Emily Boudreaux
67dde830af
Note that currently this actually slows the code down. Spinning up the threads and tearing them down is expensive
1339 lines
57 KiB
C++
1339 lines
57 KiB
C++
#pragma once
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#include "fourdst/atomic/atomicSpecies.h"
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#include "fourdst/composition/composition.h"
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#include "fourdst/logging/logging.h"
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#include "fourdst/config/config.h"
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#include "gridfire/types/types.h"
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#include "gridfire/reaction/reaction.h"
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#include "gridfire/engine/engine_abstract.h"
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#include "gridfire/screening/screening_abstract.h"
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#include "gridfire/screening/screening_types.h"
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#include "gridfire/partition/partition_abstract.h"
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#include "gridfire/engine/procedures/construction.h"
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#include "gridfire/config/config.h"
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#include <string>
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#include <unordered_map>
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#include <vector>
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#include <memory>
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#include <ranges>
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#include <functional>
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#include "cppad/cppad.hpp"
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#include "cppad/utility/sparse_rc.hpp"
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#include "cppad/speed/sparse_jac_fun.hpp"
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#include "gridfire/reaction/weak/weak_interpolator.h"
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#include "gridfire/reaction/weak/weak_rate_library.h"
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// PERF: The function getNetReactionStoichiometry returns a map of species to their stoichiometric coefficients for a given reaction.
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// this makes extra copies of the species, which is not ideal and could be optimized further.
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// Even more relevant is the member m_reactionIDMap which makes copies of a REACLIBReaction for each reaction ID.
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// REACLIBReactions are quite large data structures, so this could be a performance bottleneck.
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namespace gridfire::engine {
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/**
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* @brief Alias for CppAD AD type for double precision.
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*
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* This alias simplifies the use of the CppAD automatic differentiation type.
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*/
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typedef CppAD::AD<double> ADDouble;
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using fourdst::config::Config;
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using fourdst::logging::LogManager;
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using fourdst::constant::Constants;
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/**
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* @brief Minimum density threshold below which reactions are ignored.
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*
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* Reactions are not calculated if the density falls below this threshold.
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* This helps to improve performance by avoiding unnecessary calculations
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* in very low-density regimes.
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*/
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static constexpr double MIN_DENSITY_THRESHOLD = 1e-18;
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/**
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* @brief Minimum abundance threshold below which species are ignored.
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*
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* Species with abundances below this threshold are treated as zero in
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* reaction rate calculations. This helps to improve performance by
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* avoiding unnecessary calculations for trace species.
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*/
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static constexpr double MIN_ABUNDANCE_THRESHOLD = 1e-18;
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/**
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* @brief Minimum value for Jacobian matrix entries.
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*
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* Jacobian matrix entries with absolute values below this threshold are
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* treated as zero to maintain sparsity and improve performance.
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*/
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static constexpr double MIN_JACOBIAN_THRESHOLD = 1e-24;
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/**
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* @class GraphEngine
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* @brief A reaction network engine that uses a graph-based representation.
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*
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* The GraphEngine class implements the DynamicEngine interface using a
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* graph-based representation of the reaction network. It uses sparse
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* matrices for efficient storage and computation of the stoichiometry
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* and Jacobian matrices. Automatic differentiation (AD) is used to
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* calculate the Jacobian matrix.
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*
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* The engine supports:
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* - Calculation of the right-hand side (dY/dt) and energy generation rate.
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* - Generation and access to the Jacobian matrix.
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* - Generation and access to the stoichiometry matrix.
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* - Calculation of molar reaction flows.
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* - Access to the set of logical reactions in the network.
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* - Computation of timescales for each species.
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* - Exporting the network to DOT and CSV formats for visualization and analysis.
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*
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* @implements DynamicEngine
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*
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* @see engine_abstract.h
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*/
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class GraphEngine final : public DynamicEngine {
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public:
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/**
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* @brief Constructs a GraphEngine from a composition.
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*
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* @param composition The composition of the material.
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*
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* This constructor builds the reaction network from the given composition
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* using the `build_reaclib_nuclear_network` function.
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*
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* @see build_reaclib_nuclear_network
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*/
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explicit GraphEngine(
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const fourdst::composition::Composition &composition,
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BuildDepthType = NetworkBuildDepth::Full
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);
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explicit GraphEngine(
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const fourdst::composition::Composition &composition,
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const partition::PartitionFunction& partitionFunction,
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BuildDepthType buildDepth = NetworkBuildDepth::Full
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);
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explicit GraphEngine(
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const fourdst::composition::Composition &composition,
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const partition::PartitionFunction& partitionFunction,
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BuildDepthType buildDepth,
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NetworkConstructionFlags reactionTypes
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);
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/**
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* @brief Constructs a GraphEngine from a set of reactions.
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*
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* @param reactions The set of reactions to use in the network.
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*
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* This constructor uses the given set of reactions to construct the
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* reaction network.
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*/
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explicit GraphEngine(const reaction::ReactionSet &reactions);
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/**
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* @brief Calculates the right-hand side (dY/dt) and energy generation rate.
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*
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* @param comp Composition object containing current abundances.
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* @param T9 Temperature in units of 10^9 K.
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* @param rho Density in g/cm^3.
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* @return StepDerivatives<double> containing dY/dt and energy generation rate.
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*
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* This method calculates the time derivatives of all species and the
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* specific nuclear energy generation rate for the current state.
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*
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* @see StepDerivatives
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*/
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[[nodiscard]] std::expected<StepDerivatives<double>, engine::EngineStatus> calculateRHSAndEnergy(
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const fourdst::composition::CompositionAbstract &comp,
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double T9,
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double rho
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) const override;
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/**
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* @brief Calculates the right-hand side (dY/dt) and energy generation rate for a subset of reactions.
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*
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* @param comp Composition object containing current abundances.
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* @param T9 Temperature in units of 10^9 K.
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* @param rho Density in g/cm^3.
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* @param activeReactions The set of reactions to include in the calculation.
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* @return StepDerivatives<double> containing dY/dt and energy generation rate.
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*
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* This method calculates the time derivatives of all species and the
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* specific nuclear energy generation rate considering only the specified
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* subset of reactions. This allows for flexible calculations with
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* different reaction sets without modifying the engine's internal state.
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*
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* @see StepDerivatives
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*/
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[[nodiscard]] std::expected<StepDerivatives<double>, EngineStatus> calculateRHSAndEnergy(
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const fourdst::composition::CompositionAbstract& comp,
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double T9,
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double rho,
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const reaction::ReactionSet &activeReactions
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) const;
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/**
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* @brief Calculates the derivatives of the energy generation rate with respect to temperature and density
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*
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* @param comp Composition object containing current abundances.
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* @param T9 Temperature in units of 10^9 K.
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* @param rho Density in g/cm^3.
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* @return EnergyDerivatives struct containing the derivatives.
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*
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* This method computes the partial derivatives of the specific nuclear
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* energy generation rate with respect to temperature (∂ε/∂T) and
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* density (∂ε/∂ρ)
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*
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* @see EnergyDerivatives
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*/
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[[nodiscard]] EnergyDerivatives calculateEpsDerivatives(
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const fourdst::composition::CompositionAbstract &comp,
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double T9,
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double rho
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) const override;
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/**
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* @brief Calculates the derivatives of the energy generation rate with respect to temperature and density for a subset of reactions
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*
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* @param comp Composition object containing current abundances.
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* @param T9 Temperature in units of 10^9 K.
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* @param rho Density in g/cm^3.
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* @param activeReactions The set of reactions to include in the calculation.
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* @return EnergyDerivatives struct containing the derivatives.
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*
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* This method computes the partial derivatives of the specific nuclear
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* energy generation rate with respect to temperature (∂ε/∂T) and
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* density (∂ε/∂ρ) considering
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* only the specified subset of reactions. This allows for flexible
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* calculations with different reaction sets without modifying the
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* engine's internal state.
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*
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* @see EnergyDerivatives
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*/
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[[nodiscard]] EnergyDerivatives calculateEpsDerivatives(
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const fourdst::composition::CompositionAbstract &comp,
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double T9,
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double rho,
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const reaction::ReactionSet &activeReactions
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) const;
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/**
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* @brief Generates the Jacobian matrix for the current state.
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*
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* @param comp Composition object containing current abundances.
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* @param T9 Temperature in units of 10^9 K.
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* @param rho Density in g/cm^3.
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*
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* This method computes and stores the Jacobian matrix (∂(dY/dt)_i/∂Y_j)
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* for the current state using automatic differentiation. The matrix can
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* then be accessed via `getJacobianMatrixEntry()`.
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*
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* @see getJacobianMatrixEntry()
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*/
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[[nodiscard]] NetworkJacobian generateJacobianMatrix(
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const fourdst::composition::CompositionAbstract &comp,
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double T9,
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double rho
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) const override;
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/**
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* @brief Generates the Jacobian matrix for the current state with a specified set of active species.
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* generally this will be much faster than the full matrix generation. Here we use forward mode
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* to generate the Jacobian only for the active species.
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* @param comp The Composition object containing current abundances.
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* @param T9 The temperature in units of 10^9 K.
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* @param rho The density in g/cm^3.
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* @param activeSpecies A vector of Species objects representing the active species.
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*
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* @see getJacobianMatrixEntry()
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* @see generateJacobianMatrix()
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*/
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[[nodiscard]] NetworkJacobian generateJacobianMatrix(
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const fourdst::composition::CompositionAbstract &comp,
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double T9,
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double rho,
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const std::vector<fourdst::atomic::Species>& activeSpecies
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) const override;
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/**
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* @brief Generates the Jacobian matrix for the current state with a specified sparsity pattern.
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*
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* @param comp Composition object containing current abundances.
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* @param T9 Temperature in units of 10^9 K.
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* @param rho Density in g/cm^3.
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* @param sparsityPattern The sparsity pattern to use for the Jacobian matrix.
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*
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* This method computes and stores the Jacobian matrix (∂(dY/dt)_i/∂Y_j)
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* for the current state using automatic differentiation, taking into
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* account the provided sparsity pattern. The matrix can then be accessed
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* via `getJacobianMatrixEntry()`.
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*
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* @see getJacobianMatrixEntry()
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*/
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[[nodiscard]] NetworkJacobian generateJacobianMatrix(
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const fourdst::composition::CompositionAbstract &comp,
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double T9,
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double rho,
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const SparsityPattern &sparsityPattern
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) const override;
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/**
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* @brief Generates the stoichiometry matrix for the network.
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*
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* This method computes and stores the stoichiometry matrix,
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* which encodes the net change of each species in each reaction.
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*/
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void generateStoichiometryMatrix() override;
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/**
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* @brief Calculates the molar reaction flow for a given reaction.
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*
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* @param reaction The reaction for which to calculate the flow.
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* @param comp Composition object containing current abundances.
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* @param T9 Temperature in units of 10^9 K.
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* @param rho Density in g/cm^3.
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* @return Molar flow rate for the reaction (e.g., mol/g/s).
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*
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* This method computes the net rate at which the given reaction proceeds
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* under the current state.
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*
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*/
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[[nodiscard]] double calculateMolarReactionFlow(
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const reaction::Reaction& reaction,
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const fourdst::composition::CompositionAbstract &comp,
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double T9,
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double rho
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) const override;
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/**
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* @brief Gets the list of species in the network.
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* @return Vector of Species objects representing all network species.
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*/
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[[nodiscard]] const std::vector<fourdst::atomic::Species>& getNetworkSpecies() const override;
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/**
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* @brief Gets the set of logical reactions in the network.
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* @return Reference to the LogicalReactionSet containing all reactions.
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*/
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[[nodiscard]] const reaction::ReactionSet& getNetworkReactions() const override;
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/**
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* @brief Sets the reactions for the network.
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*
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* @param reactions The set of reactions to use in the network.
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*
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* This method replaces the current set of reactions in the network
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* with the provided set. It marks the engine as stale, requiring
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* regeneration of matrices and recalculation of rates.
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*/
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void setNetworkReactions(const reaction::ReactionSet& reactions) override;
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/**
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* @brief Gets the net stoichiometry for a given reaction.
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*
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* @param reaction The reaction for which to get the stoichiometry.
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* @return Map of species to their stoichiometric coefficients.
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*/
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[[nodiscard]] static std::unordered_map<fourdst::atomic::Species, int> getNetReactionStoichiometry(
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const reaction::Reaction& reaction
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);
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/**
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* @brief Gets an entry from the stoichiometry matrix.
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*
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* @param species Species to look up stoichiometry for.
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* @param reaction Reaction to find.
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* @return Stoichiometric coefficient for the species in the reaction.
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*
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* The stoichiometry matrix must have been generated by `generateStoichiometryMatrix()`.
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*
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* @see generateStoichiometryMatrix()
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*/
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[[nodiscard]] int getStoichiometryMatrixEntry(
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const fourdst::atomic::Species& species,
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const reaction::Reaction& reaction
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) const override;
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/**
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* @brief Computes timescales for all species in the network.
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*
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* @param comp Composition object containing current abundances.
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* @param T9 Temperature in units of 10^9 K.
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* @param rho Density in g/cm^3.
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* @return Map from Species to their characteristic timescales (s).
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*
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* This method estimates the timescale for abundance change of each species,
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* which can be used for timestep control or diagnostics.
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*/
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[[nodiscard]] std::expected<std::unordered_map<fourdst::atomic::Species, double>, engine::EngineStatus>
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getSpeciesTimescales(
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const fourdst::composition::CompositionAbstract &comp,
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double T9,
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double rho
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) const override;
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/**
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* @brief Computes timescales for all species in the network considering a subset of reactions.
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*
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* @param comp Composition object containing current abundances.
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* @param T9 Temperature in units of 10^9 K.
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* @param rho Density in g/cm^3.
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* @param activeReactions The set of reactions to include in the calculation.
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* @return Map from Species to their characteristic timescales (s).
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*
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* This method estimates the timescale for abundance change of each species,
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* considering only the specified subset of reactions. This allows for flexible
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* calculations with different reaction sets without modifying the engine's internal state.
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*/
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[[nodiscard]] std::expected<std::unordered_map<fourdst::atomic::Species, double>, EngineStatus> getSpeciesTimescales(
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const fourdst::composition::CompositionAbstract &comp,
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double T9,
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double rho,
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const reaction::ReactionSet &activeReactions
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) const;
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/**
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* @brief Computes destruction timescales for all species in the network.
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*
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* @param comp Composition object containing current abundances.
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* @param T9 Temperature in units of 10^9 K.
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* @param rho Density in g/cm^3.
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* @return Map from Species to their destruction timescales (s).
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*
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* This method estimates the destruction timescale for each species,
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* which can be useful for understanding reaction flows and equilibrium states.
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*/
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[[nodiscard]] std::expected<std::unordered_map<fourdst::atomic::Species, double>, engine::EngineStatus>
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getSpeciesDestructionTimescales(
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const fourdst::composition::CompositionAbstract &comp,
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double T9,
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double rho
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) const override;
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/**
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* @brief Computes destruction timescales for all species in the network considering a subset of reactions.
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*
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* @param comp Composition object containing current abundances.
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* @param T9 Temperature in units of 10^9 K.
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* @param rho Density in g/cm^3.
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* @param activeReactions The set of reactions to include in the calculation.
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* @return Map from Species to their destruction timescales (s).
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*
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* This method estimates the destruction timescale for each species,
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* considering only the specified subset of reactions. This allows for flexible
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* calculations with different reaction sets without modifying the engine's internal state.
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*/
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[[nodiscard]] std::expected<std::unordered_map<fourdst::atomic::Species, double>, EngineStatus> getSpeciesDestructionTimescales(
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const fourdst::composition::CompositionAbstract &comp,
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double T9,
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double rho,
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const reaction::ReactionSet &activeReactions
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) const;
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/**
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* @brief Updates the state of the network and the composition to be usable for the current network.
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*
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* @details For graph engine all this does is ensure that the returned composition has all the species in the network registered.
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* if a species was already in the composition is will keep its abundance, otherwise it will be added with zero abundance.
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*
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* @param netIn The input netIn to use, this includes the composition, temperature, and density
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*
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* @return The updated composition that includes all species in the network.
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*/
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fourdst::composition::Composition update(
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const NetIn &netIn
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) override;
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|
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/**
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* @brief Checks if the engine view is stale and needs to be updated.
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*
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* @param netIn The current network input (unused).
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* @return True if the view is stale, false otherwise.
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*
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* @deprecated This method is deprecated and will be removed in future versions.
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* Stale states are returned as part of the results of methods that
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* require the ability to report them.
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*/
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[[deprecated]] bool isStale(
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const NetIn &netIn
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) override;
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/**
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* @brief Checks if a given species is involved in the network.
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*
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* @param species The species to check.
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* @return True if the species is involved in the network, false otherwise.
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*/
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[[nodiscard]] bool involvesSpecies(
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const fourdst::atomic::Species& species
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) const;
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/**
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* @brief Exports the network to a DOT file for visualization.
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*
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* @param filename The name of the DOT file to create.
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*
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* This method generates a DOT file that can be used to visualize the
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* reaction network as a graph. The DOT file can be converted to a
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* graphical image using Graphviz.
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*
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* @throws std::runtime_error If the file cannot be opened for writing.
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*
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* Example usage:
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* @code
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* engine.exportToDot("network.dot");
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* @endcode
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*/
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void exportToDot(
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const std::string& filename
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) const;
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/**
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* @brief Exports the network to a CSV file for analysis.
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*
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* @param filename The name of the CSV file to create.
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*
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* This method generates a CSV file containing information about the
|
|
* reactions in the network, including the reactants, products, Q-value,
|
|
* and reaction rate coefficients.
|
|
*
|
|
* @throws std::runtime_error If the file cannot be opened for writing.
|
|
*
|
|
* Example usage:
|
|
* @code
|
|
* engine.exportToCSV("network.csv");
|
|
* @endcode
|
|
*/
|
|
void exportToCSV(
|
|
const std::string& filename
|
|
) const;
|
|
|
|
/**
|
|
* @brief Sets the electron screening model for reaction rate calculations.
|
|
*
|
|
* @param model The type of screening model to use.
|
|
*
|
|
* This method allows changing the screening model at runtime. Screening corrections
|
|
* account for the electrostatic shielding of nuclei by electrons, which affects
|
|
* reaction rates in dense stellar plasmas.
|
|
*/
|
|
void setScreeningModel(
|
|
screening::ScreeningType model
|
|
) override;
|
|
|
|
/**
|
|
* @brief Gets the current electron screening model.
|
|
*
|
|
* @return The currently active screening model type.
|
|
*
|
|
* Example usage:
|
|
* @code
|
|
* screening::ScreeningType currentModel = engine.getScreeningModel();
|
|
* @endcode
|
|
*/
|
|
[[nodiscard]] screening::ScreeningType getScreeningModel() const override;
|
|
|
|
/**
|
|
* @brief Sets whether to precompute reaction rates.
|
|
*
|
|
* @param precompute True to enable precomputation, false to disable.
|
|
*
|
|
* This method allows enabling or disabling precomputation of reaction rates
|
|
* for performance optimization. When enabled, reaction rates are computed
|
|
* once and stored for later use.
|
|
*
|
|
* @post If precomputation is enabled, reaction rates will be precomputed and cached.
|
|
* If disabled, reaction rates will be computed on-the-fly as needed.
|
|
*/
|
|
void setPrecomputation(
|
|
bool precompute
|
|
);
|
|
|
|
/**
|
|
* @brief Checks if precomputation of reaction rates is enabled.
|
|
*
|
|
* @return True if precomputation is enabled, false otherwise.
|
|
*
|
|
* This method allows checking the current state of precomputation for
|
|
* reaction rates in the engine.
|
|
*/
|
|
[[nodiscard]] bool isPrecomputationEnabled() const;
|
|
|
|
/**
|
|
* @brief Gets the partition function used for reaction rate calculations.
|
|
*
|
|
* @return Reference to the PartitionFunction object.
|
|
*
|
|
* This method provides access to the partition function used in the engine,
|
|
* which is essential for calculating thermodynamic properties and reaction rates.
|
|
*/
|
|
[[nodiscard]] const partition::PartitionFunction& getPartitionFunction() const;
|
|
|
|
/**
|
|
* @brief Calculates the reverse rate for a given reaction.
|
|
*
|
|
* @param reaction The reaction for which to calculate the reverse rate.
|
|
* @param T9 Temperature in units of 10^9 K.
|
|
* @param rho
|
|
* @param comp Composition object containing current abundances.
|
|
* @return Reverse rate for the reaction (e.g., mol/g/s).
|
|
*
|
|
* This method computes the reverse rate based on the forward rate and
|
|
* thermodynamic properties of the reaction.
|
|
*/
|
|
[[nodiscard]] double calculateReverseRate(
|
|
const reaction::Reaction &reaction,
|
|
double T9,
|
|
double rho,
|
|
const fourdst::composition::CompositionAbstract &comp
|
|
) const;
|
|
|
|
/**
|
|
* @brief Calculates the reverse rate for a two-body reaction.
|
|
*
|
|
* @param reaction The reaction for which to calculate the reverse rate.
|
|
* @param T9 Temperature in units of 10^9 K.
|
|
* @param forwardRate The forward rate of the reaction.
|
|
* @param expFactor Exponential factor for the reaction.
|
|
* @return Reverse rate for the two-body reaction (e.g., mol/g/s).
|
|
*
|
|
* This method computes the reverse rate using the forward rate and
|
|
* thermodynamic properties of the reaction.
|
|
*/
|
|
[[nodiscard]] double calculateReverseRateTwoBody(
|
|
const reaction::Reaction &reaction,
|
|
double T9,
|
|
double forwardRate,
|
|
double expFactor
|
|
) const;
|
|
|
|
/**
|
|
* @brief Calculates the derivative of the reverse rate for a two-body reaction with respect to temperature.
|
|
*
|
|
* @param reaction The reaction for which to calculate the derivative.
|
|
* @param T9 Temperature in units of 10^9 K.
|
|
* @param rho Density in g/cm^3.
|
|
* @param comp Composition object containing current abundances.
|
|
* @param reverseRate The reverse rate of the reaction.
|
|
* @return Derivative of the reverse rate with respect to temperature.
|
|
*
|
|
* This method computes the derivative of the reverse rate using automatic differentiation.
|
|
*/
|
|
[[nodiscard]] double calculateReverseRateTwoBodyDerivative(
|
|
const reaction::Reaction &reaction,
|
|
double T9,
|
|
double rho,
|
|
const fourdst::composition::Composition& comp,
|
|
double reverseRate
|
|
) const;
|
|
|
|
/**
|
|
* @brief Checks if reverse reactions are enabled.
|
|
*
|
|
* @return True if reverse reactions are enabled, false otherwise.
|
|
*
|
|
* This method allows checking whether the engine is configured to use
|
|
* reverse reactions in its calculations.
|
|
*/
|
|
[[nodiscard]] bool isUsingReverseReactions() const;
|
|
|
|
/**
|
|
* @brief Sets whether to use reverse reactions in the engine.
|
|
*
|
|
* @param useReverse True to enable reverse reactions, false to disable.
|
|
*
|
|
* This method allows enabling or disabling reverse reactions in the engine.
|
|
* If disabled, only forward reactions will be considered in calculations.
|
|
*
|
|
* @post If reverse reactions are enabled, the engine will consider both
|
|
* forward and reverse reactions in its calculations. If disabled,
|
|
* only forward reactions will be considered.
|
|
*/
|
|
void setUseReverseReactions(
|
|
bool useReverse
|
|
);
|
|
|
|
/**
|
|
* @brief Gets the index of a species in the network.
|
|
*
|
|
* @param species The species for which to get the index.
|
|
* @return Index of the species in the network, or -1 if not found.
|
|
*
|
|
* This method returns the index of the given species in the network's
|
|
* species vector. If the species is not found, it returns -1.
|
|
*/
|
|
[[nodiscard]] size_t getSpeciesIndex(
|
|
const fourdst::atomic::Species &species
|
|
) const override;
|
|
|
|
/**
|
|
* @brief Maps the NetIn object to a vector of molar abundances.
|
|
*
|
|
* @param netIn The NetIn object containing the input conditions.
|
|
* @return Vector of molar abundances corresponding to the species in the network.
|
|
*
|
|
* This method converts the NetIn object into a vector of molar abundances
|
|
* for each species in the network, which can be used for further calculations.
|
|
*/
|
|
[[deprecated]] [[nodiscard]] std::vector<double> mapNetInToMolarAbundanceVector(
|
|
const NetIn &netIn
|
|
) const override;
|
|
|
|
/**
|
|
* @brief Prepares the engine for calculations with initial conditions.
|
|
*
|
|
* @param netIn The input conditions for the network.
|
|
* @return PrimingReport containing information about the priming process.
|
|
*
|
|
* This method initializes the engine with the provided input conditions,
|
|
* setting up reactions, species, and precomputing necessary data.
|
|
*/
|
|
[[nodiscard]] PrimingReport primeEngine(
|
|
const NetIn &netIn
|
|
) override;
|
|
|
|
/**
|
|
* @brief Gets the depth of the network.
|
|
*
|
|
* @return The build depth of the network.
|
|
*
|
|
* This method returns the current build depth of the reaction network,
|
|
* which indicates how many levels of reactions are included in the network.
|
|
*/
|
|
[[nodiscard]] BuildDepthType getDepth() const override;
|
|
|
|
/**
|
|
* @brief Rebuilds the reaction network based on a new composition.
|
|
*
|
|
* @param comp The new composition to use for rebuilding the network.
|
|
* @param depth The build depth to use for the network.
|
|
*
|
|
* This method rebuilds the reaction network using the provided composition
|
|
* and build depth. It updates all internal data structures accordingly.
|
|
*/
|
|
void rebuild(
|
|
const fourdst::composition::CompositionAbstract &comp,
|
|
BuildDepthType depth
|
|
) override;
|
|
|
|
/**
|
|
* @brief This will return the input comp with the molar abundances of any species not registered in that but
|
|
* registered in the engine active species set to 0.0.
|
|
* @note Effectively this method does not change input composition; rather it ensures that all species which
|
|
* can be tracked by an instance of GraphEngine are registered in the composition object.
|
|
* @note If a species is in the input comp but not in the network
|
|
* @param comp Input Composition
|
|
* @param T9
|
|
* @param rho
|
|
* @param T9
|
|
* @param rho
|
|
* @return A new composition where all members of the active species set are registered. And any members not in comp
|
|
* have a molar abundance set to 0.
|
|
* @throws BadCollectionError If the input composition contains species not present in the network species set
|
|
*/
|
|
fourdst::composition::Composition collectComposition(const fourdst::composition::CompositionAbstract &comp, double T9, double rho) const override;
|
|
|
|
/**
|
|
* @brief Gets the status of a species in the network.
|
|
*
|
|
* @param species The species for which to get the status.
|
|
* @return SpeciesStatus indicating the status of the species.
|
|
*
|
|
* This method checks if the given species is part of the network and
|
|
* returns its status (e.g., Active, Inactive, NotFound).
|
|
*/
|
|
[[nodiscard]]
|
|
SpeciesStatus getSpeciesStatus(const fourdst::atomic::Species &species) const override;
|
|
|
|
[[nodiscard]] bool get_store_intermediate_reaction_contributions() const {
|
|
return m_store_intermediate_reaction_contributions;
|
|
}
|
|
|
|
void set_store_intermediate_reaction_contributions(const bool value) {
|
|
m_store_intermediate_reaction_contributions = value;
|
|
}
|
|
|
|
|
|
private:
|
|
struct PrecomputedReaction {
|
|
// Forward cacheing
|
|
size_t reaction_index{};
|
|
reaction::ReactionType reaction_type{};
|
|
uint64_t reaction_hash{};
|
|
std::vector<size_t> unique_reactant_indices{};
|
|
std::vector<int> reactant_powers{};
|
|
double symmetry_factor{};
|
|
std::vector<size_t> affected_species_indices{};
|
|
std::vector<int> stoichiometric_coefficients{};
|
|
|
|
// Reverse cacheing
|
|
std::vector<size_t> unique_product_indices{}; ///< Unique product indices for reverse reactions.
|
|
std::vector<int> product_powers{}; ///< Powers of each unique product in the reverse reaction.
|
|
double reverse_symmetry_factor{}; ///< Symmetry factor for reverse reactions.
|
|
};
|
|
|
|
struct constants {
|
|
const double u = Constants::getInstance().get("u").value; ///< Atomic mass unit in g.
|
|
const double Na = Constants::getInstance().get("N_a").value; ///< Avogadro's number.
|
|
const double c = Constants::getInstance().get("c").value; ///< Speed of light in cm/s.
|
|
const double kB = Constants::getInstance().get("kB").value; ///< Boltzmann constant in erg/K.
|
|
const double MeV_to_erg = Constants::getInstance().get("MeV_to_erg").value; ///< Conversion factor from MeV to erg.
|
|
};
|
|
|
|
enum class JacobianMatrixState {
|
|
UNINITIALIZED,
|
|
STALE,
|
|
READY_DENSE,
|
|
READY_SPARSE
|
|
};
|
|
|
|
std::unordered_map<JacobianMatrixState, std::string> m_jacobianMatrixStateNameMap = {
|
|
{JacobianMatrixState::UNINITIALIZED, "Uninitialized"},
|
|
{JacobianMatrixState::STALE, "Stale"},
|
|
{JacobianMatrixState::READY_DENSE, "Ready (dense)"},
|
|
{JacobianMatrixState::READY_SPARSE, "Ready (sparse)"},
|
|
};
|
|
private:
|
|
class AtomicReverseRate final : public CppAD::atomic_base<double> {
|
|
public:
|
|
AtomicReverseRate(
|
|
const reaction::Reaction& reaction,
|
|
const GraphEngine& engine
|
|
):
|
|
atomic_base<double>("AtomicReverseRate"),
|
|
m_reaction(reaction),
|
|
m_engine(engine) {}
|
|
|
|
bool forward(
|
|
size_t p,
|
|
size_t q,
|
|
const CppAD::vector<bool>& vx,
|
|
CppAD::vector<bool>& vy,
|
|
const CppAD::vector<double>& tx,
|
|
CppAD::vector<double>& ty
|
|
) override;
|
|
bool reverse(
|
|
size_t q,
|
|
const CppAD::vector<double>& tx,
|
|
const CppAD::vector<double>& ty,
|
|
CppAD::vector<double>& px,
|
|
const CppAD::vector<double>& py
|
|
) override;
|
|
bool for_sparse_jac(
|
|
size_t q,
|
|
const CppAD::vector<std::set<size_t>>&r,
|
|
CppAD::vector<std::set<size_t>>& s
|
|
) override;
|
|
bool rev_sparse_jac(
|
|
size_t q,
|
|
const CppAD::vector<std::set<size_t>>&rt,
|
|
CppAD::vector<std::set<size_t>>& st
|
|
) override;
|
|
bool for_sparse_jac(
|
|
size_t q,
|
|
const CppAD::vector<bool> &r,
|
|
CppAD::vector<bool> &s,
|
|
const CppAD::vector<double> &x
|
|
) override;
|
|
bool rev_sparse_jac(
|
|
size_t q,
|
|
const CppAD::vector<bool> &rt,
|
|
CppAD::vector<bool> &st,
|
|
const CppAD::vector<double> &x
|
|
) override;
|
|
|
|
private:
|
|
const reaction::Reaction& m_reaction;
|
|
const GraphEngine& m_engine;
|
|
};
|
|
|
|
struct PrecomputationKernelResults {
|
|
std::vector<double> dydt_vector;
|
|
double total_neutrino_energy_loss_rate{0.0};
|
|
double total_neutrino_flux{0.0};
|
|
};
|
|
private:
|
|
Config<config::GridFireConfig> m_config;
|
|
quill::Logger* m_logger = LogManager::getInstance().getLogger("log");
|
|
|
|
constants m_constants;
|
|
|
|
rates::weak::WeakRateInterpolator m_weakRateInterpolator; ///< Interpolator for weak reaction rates.
|
|
|
|
reaction::ReactionSet m_reactions; ///< Set of REACLIB reactions in the network.
|
|
std::unordered_map<std::string_view, reaction::Reaction*> m_reactionIDMap; ///< Map from reaction ID to REACLIBReaction. //PERF: This makes copies of REACLIBReaction and could be a performance bottleneck.
|
|
|
|
std::vector<fourdst::atomic::Species> m_networkSpecies; ///< Vector of unique species in the network.
|
|
std::unordered_map<std::string_view, fourdst::atomic::Species> m_networkSpeciesMap; ///< Map from species name to Species object.
|
|
std::unordered_map<fourdst::atomic::Species, size_t> m_speciesToIndexMap; ///< Map from species to their index in the stoichiometry matrix.
|
|
std::unordered_map<size_t, fourdst::atomic::Species> m_indexToSpeciesMap; ///< Map from index to species in the stoichiometry matrix.
|
|
|
|
|
|
mutable CppAD::ADFun<double> m_rhsADFun; ///< CppAD function for the right-hand side of the ODE.
|
|
mutable CppAD::ADFun<double> m_epsADFun; ///< CppAD function for the energy generation rate.
|
|
mutable CppAD::sparse_jac_work m_jac_work; ///< Work object for sparse Jacobian calculations.
|
|
mutable std::vector<double> m_local_abundance_cache;
|
|
|
|
bool m_has_been_primed = false; ///< Flag indicating if the engine has been primed.
|
|
|
|
CppAD::sparse_rc<std::vector<size_t>> m_full_jacobian_sparsity_pattern; ///< Full sparsity pattern for the Jacobian matrix.
|
|
std::set<std::pair<size_t, size_t>> m_full_sparsity_set; ///< For quick lookups of the base sparsity pattern
|
|
|
|
std::vector<std::unique_ptr<AtomicReverseRate>> m_atomicReverseRates;
|
|
|
|
screening::ScreeningType m_screeningType = screening::ScreeningType::BARE; ///< Screening type for the reaction network. Default to no screening.
|
|
std::unique_ptr<screening::ScreeningModel> m_screeningModel = screening::selectScreeningModel(m_screeningType);
|
|
|
|
bool m_usePrecomputation = true; ///< Flag to enable or disable using precomputed reactions for efficiency. Mathematically, this should not change the results. Generally end users should not need to change this.
|
|
bool m_useReverseReactions = true; ///< Flag to enable or disable reverse reactions. If false, only forward reactions are considered.
|
|
bool m_store_intermediate_reaction_contributions = false; ///< Flag to enable or disable storing intermediate reaction contributions for debugging.
|
|
|
|
BuildDepthType m_depth;
|
|
|
|
std::vector<PrecomputedReaction> m_precomputedReactions; ///< Precomputed reactions for efficiency.
|
|
std::unordered_map<uint64_t, size_t> m_precomputedReactionIndexMap; ///< Set of hashed precomputed reactions for quick lookup.
|
|
std::unique_ptr<partition::PartitionFunction> m_partitionFunction; ///< Partition function for the network.
|
|
|
|
private:
|
|
/**
|
|
* @brief Synchronizes the internal maps.
|
|
*
|
|
* This method synchronizes the internal maps used by the engine,
|
|
* including the species map, reaction ID map, and species-to-index map.
|
|
* It also generates the stoichiometry matrix and records the AD tape.
|
|
*/
|
|
void syncInternalMaps();
|
|
|
|
/**
|
|
* @brief Collects the unique species in the network.
|
|
*
|
|
* This method collects the unique species in the network from the
|
|
* reactants and products of all reactions.
|
|
*/
|
|
void collectNetworkSpecies();
|
|
|
|
/**
|
|
* @brief Populates the reaction ID map.
|
|
*
|
|
* This method populates the reaction ID map, which maps reaction IDs
|
|
* to REACLIBReaction objects.
|
|
*/
|
|
void populateReactionIDMap();
|
|
|
|
/**
|
|
* @brief Populates the species-to-index map.
|
|
*
|
|
* This method populates the species-to-index map, which maps species
|
|
* to their index in the stoichiometry matrix.
|
|
*/
|
|
void populateSpeciesToIndexMap();
|
|
|
|
|
|
/**
|
|
* @brief Records the AD tape for the right-hand side of the ODE.
|
|
*
|
|
* This method records the AD tape for the right-hand side of the ODE,
|
|
* which is used to calculate the Jacobian matrix using automatic
|
|
* differentiation.
|
|
*
|
|
* @throws std::runtime_error If there are no species in the network.
|
|
*/
|
|
void recordADTape() const;
|
|
|
|
void collectAtomicReverseRateAtomicBases();
|
|
|
|
void precomputeNetwork();
|
|
|
|
|
|
/**
|
|
* @brief Validates mass and charge conservation across all reactions.
|
|
*
|
|
* @return True if all reactions conserve mass and charge, false otherwise.
|
|
*
|
|
* This method checks that all reactions in the network conserve mass
|
|
* and charge. If any reaction does not conserve mass or charge, an
|
|
* error message is logged and false is returned.
|
|
*/
|
|
[[nodiscard]] bool validateConservation() const;
|
|
|
|
double compute_reaction_flow(
|
|
const std::vector<double> &local_abundances,
|
|
const std::vector<double> &screening_factors,
|
|
const std::vector<double> &bare_rates,
|
|
const std::vector<double> &bare_reverse_rates,
|
|
double rho,
|
|
size_t reactionCounter,
|
|
const reaction::Reaction &reaction,
|
|
size_t reactionIndex,
|
|
const PrecomputedReaction &precomputedReaction
|
|
) const;
|
|
|
|
std::pair<double, double> compute_neutrino_fluxes(
|
|
double netFlow,
|
|
const reaction::Reaction &reaction) const;
|
|
|
|
PrecomputationKernelResults accumulate_flows_serial(
|
|
const std::vector<double>& local_abundances,
|
|
const std::vector<double>& screening_factors,
|
|
const std::vector<double>& bare_rates,
|
|
const std::vector<double>& bare_reverse_rates,
|
|
double rho,
|
|
const reaction::ReactionSet& activeReactions
|
|
) const;
|
|
|
|
#ifdef GRIDFIRE_USE_OPENMP
|
|
PrecomputationKernelResults accumulate_flows_parallel(
|
|
const std::vector<double>& local_abundances,
|
|
const std::vector<double>& screening_factors,
|
|
const std::vector<double>& bare_rates,
|
|
const std::vector<double>& bare_reverse_rates,
|
|
double rho,
|
|
const reaction::ReactionSet& activeReactions
|
|
) const;
|
|
#endif
|
|
|
|
|
|
[[nodiscard]] StepDerivatives<double> calculateAllDerivativesUsingPrecomputation(
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const fourdst::composition::CompositionAbstract &comp,
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const std::vector<double> &bare_rates,
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const std::vector<double> &bare_reverse_rates,
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double T9,
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double rho, const reaction::ReactionSet &activeReactions
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) const;
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/**
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* @brief Calculates the molar reaction flow for a given reaction.
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*
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* @tparam T The numeric type to use for the calculation.
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* @param reaction The reaction for which to calculate the flow.
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* @param Y Vector of molar abundances for all species in the network.
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* @param T9 Temperature in units of 10^9 K.
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* @param rho Density in g/cm^3.
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* @param Ye
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* @param mue
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* @param speciesIDLookup
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* @return Molar flow rate for the reaction (e.g., mol/g/s).
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*
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* This method computes the net rate at which the given reaction proceeds
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* under the current state.
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*/
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template <IsArithmeticOrAD T>
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T calculateMolarReactionFlow(
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const reaction::Reaction &reaction,
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const std::vector<T>& Y,
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T T9,
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T rho,
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T Ye,
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T mue,
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const std::function<std::optional<size_t>(const fourdst::atomic::Species &)>&speciesIDLookup
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) const;
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template<IsArithmeticOrAD T>
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T calculateReverseMolarReactionFlow(
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T T9,
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T rho,
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std::vector<T> screeningFactors,
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const std::vector<T>& Y,
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size_t reactionIndex,
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const reaction::Reaction &reaction
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) const;
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/**
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* @brief Calculates all derivatives (dY/dt) and the energy generation rate.
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*
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* @tparam T The numeric type to use for the calculation.
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* @param Y_in Vector of molar abundances for all species in the network.
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* @param T9 Temperature in units of 10^9 K.
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* @param rho Density in g/cm^3.
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* @param Ye
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* @param mue
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* @param speciesLookup
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* @param reactionLookup
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* @return StepDerivatives<T> containing dY/dt and energy generation rate.
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*
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* This method calculates the time derivatives of all species and the
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* specific nuclear energy generation rate for the current state.
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*/
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template<IsArithmeticOrAD T>
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[[nodiscard]] StepDerivatives<T> calculateAllDerivatives(
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const std::vector<T>& Y_in,
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T T9,
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T rho,
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T Ye,
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T mue,
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std::function<std::optional<size_t>(const fourdst::atomic::Species &)> speciesLookup, const std::function<bool(const
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reaction::Reaction &)>& reactionLookup
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) const;
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};
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template <IsArithmeticOrAD T>
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T GraphEngine::calculateReverseMolarReactionFlow(
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T T9,
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T rho,
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std::vector<T> screeningFactors,
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const std::vector<T>& Y,
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size_t reactionIndex,
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const reaction::Reaction &reaction
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) const {
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if (!m_useReverseReactions) {
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return static_cast<T>(0.0); // If reverse reactions are not used, return zero
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}
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T reverseMolarFlow = static_cast<T>(0.0);
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if (reaction.qValue() != 0.0) {
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T reverseRateConstant = static_cast<T>(0.0);
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if constexpr (std::is_same_v<T, ADDouble>) { // Check if T is an AD type at compile time
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const auto& atomic_func_ptr = m_atomicReverseRates[reactionIndex];
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if (atomic_func_ptr != nullptr) {
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// A. Instantiate the atomic operator for the specific reaction
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// B. Marshal the input vector
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std::vector<T> ax = { T9 };
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std::vector<T> ay(1);
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(*atomic_func_ptr)(ax, ay);
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reverseRateConstant = static_cast<T>(ay[0]);
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} else {
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return reverseMolarFlow; // If no atomic function is available, return zero
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}
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} else { // The case where T is of type double
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// A,B If not calling with an AD type, calculate the reverse rate directly
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std::vector<std::string> symbols;
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symbols.reserve(m_networkSpecies.size());
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for (const auto& species : m_networkSpecies) {
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symbols.emplace_back(species.name());
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}
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std::vector<double> X;
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X.reserve(m_networkSpecies.size());
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for (const auto& species: m_networkSpecies) {
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double Xi = species.mass() * Y[m_speciesToIndexMap.at(species)];
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X.push_back(Xi);
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}
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fourdst::composition::Composition comp(symbols, X);
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reverseRateConstant = calculateReverseRate(reaction, T9, rho, comp);
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}
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// C. Get product multiplicities
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std::unordered_map<fourdst::atomic::Species, int> productCounts;
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for (const auto& product : reaction.products()) {
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productCounts[product]++;
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}
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// D. Calculate the symmetry factor
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T reverseSymmetryFactor = static_cast<T>(1.0);
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for (const auto &count: productCounts | std::views::values) {
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reverseSymmetryFactor /= static_cast<T>(std::tgamma(static_cast<double>(count + 1))); // Gamma function for factorial
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}
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// E. Calculate the abundance term
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T productAbundanceTerm = static_cast<T>(1.0);
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for (const auto& [species, count] : productCounts) {
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const size_t speciesIndex = m_speciesToIndexMap.at(species);
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productAbundanceTerm *= CppAD::pow(Y[speciesIndex], count);
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}
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// F. Determine the power for the density term
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const size_t num_products = reaction.products().size();
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const T rho_power = CppAD::pow(rho, static_cast<T>(num_products > 1 ? num_products - 1 : 0)); // Density raised to the power of (N-1) for N products
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// G. Assemble the reverse molar flow rate
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reverseMolarFlow = screeningFactors[reactionIndex] *
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reverseRateConstant *
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productAbundanceTerm *
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reverseSymmetryFactor *
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rho_power;
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}
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return reverseMolarFlow;
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}
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template<IsArithmeticOrAD T>
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StepDerivatives<T> GraphEngine::calculateAllDerivatives(
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const std::vector<T>& Y_in,
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const T T9,
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const T rho,
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const T Ye,
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const T mue,
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const std::function<std::optional<size_t>(const fourdst::atomic::Species &)> speciesLookup,
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const std::function<bool(const reaction::Reaction &)>& reactionLookup
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) const {
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std::vector<T> screeningFactors = m_screeningModel->calculateScreeningFactors(
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m_reactions,
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m_networkSpecies,
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Y_in,
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T9,
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rho
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);
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// --- Setup output derivatives structure ---
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// We use a vector internally since indexed lookups are much cheeper, O(1)
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std::vector<T> dydt_vec;
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dydt_vec.resize(m_reactions.size(), static_cast<T>(0.0));
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// --- AD Pre-setup (flags to control conditionals in an AD safe / branch aware manner) ---
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// ----- Constants for AD safe calculations ---
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const T zero = static_cast<T>(0.0);
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const T one = static_cast<T>(1.0);
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// ----- Initialize variables for molar concentration product and thresholds ---
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// Note: the logic here is that we use CppAD::CondExprLt to test thresholds and if they are less we set the flag
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// to zero so that the final returned reaction flow is 0. This is as opposed to standard if statements
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// which create branches that break the AD tape.
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const T rho_threshold = static_cast<T>(MIN_DENSITY_THRESHOLD);
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// --- Check if the density is below the threshold where we ignore reactions ---
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T threshold_flag = CppAD::CondExpLt(rho, rho_threshold, zero, one); // If rho < threshold, set flag to 0
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std::vector<T> Y = Y_in;
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for (size_t i = 0; i < m_networkSpecies.size(); ++i) {
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// We use CppAD::CondExpLt to handle AD taping and prevent branching
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// Note that while this is syntactically more complex this is equivalent to
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// if (Y[i] < 0) {Y[i] = 0;}
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// The issue is that this would introduce a branch which would require the auto diff tape to be re-recorded
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// each timestep, which is very inefficient.
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Y[i] = CppAD::CondExpLt(Y[i], zero, zero, Y[i]); // Ensure no negative abundances
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}
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const T u = static_cast<T>(m_constants.u); // Atomic mass unit in grams
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const T N_A = static_cast<T>(m_constants.Na); // Avogadro's number in mol^-1
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const T c = static_cast<T>(m_constants.c); // Speed of light in cm/s
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// --- SINGLE LOOP OVER ALL REACTIONS ---
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StepDerivatives<T> result{};
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for (size_t reactionIndex = 0; reactionIndex < m_reactions.size(); ++reactionIndex) {
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bool skipReaction = false;
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const auto& reaction = m_reactions[reactionIndex];
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if (!reactionLookup(reaction)) {
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continue; // Skip this reaction if not in the "active" reaction set
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}
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for (const auto& reactant : reaction.reactant_species()) {
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if (!speciesLookup(reactant).has_value()) {
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skipReaction = true;
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break;
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}
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}
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if (skipReaction) {
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continue; // Skip this reaction if any reactant is not present
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}
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// 1. Calculate forward reaction rate
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const T forwardMolarReactionFlow = screeningFactors[reactionIndex] *
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calculateMolarReactionFlow<T>(
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reaction,
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Y,
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T9,
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rho,
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Ye,
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mue,
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speciesLookup
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);
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// 2. Calculate reverse reaction rate
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T reverseMolarFlow = static_cast<T>(0.0);
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// Do not calculate reverse flow for weak reactions since photodisintegration does not apply
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if ((reaction.type() == reaction::ReactionType::LOGICAL_REACLIB || reaction.type() == reaction::ReactionType::REACLIB) && m_useReverseReactions) {
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reverseMolarFlow = calculateReverseMolarReactionFlow<T>(
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T9,
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rho,
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screeningFactors,
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Y,
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reactionIndex,
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reaction
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);
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}
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const T molarReactionFlow = forwardMolarReactionFlow - reverseMolarFlow; // Net molar reaction flow
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// 3. Use the rate to update all relevant species derivatives (dY/dt)
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for (size_t speciesIdx = 0; speciesIdx < m_networkSpecies.size(); ++speciesIdx) {
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const auto& species = m_networkSpecies[speciesIdx];
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const T nu_ij = static_cast<T>(reaction.stoichiometry(species));
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const T dydt_increment = threshold_flag * molarReactionFlow * nu_ij;
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dydt_vec[speciesIdx] += dydt_increment;
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if (m_store_intermediate_reaction_contributions) {
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result.reactionContributions.value()[species][std::string(reaction.id())] = dydt_increment;
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}
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}
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}
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T massProductionRate = static_cast<T>(0.0); // [mol][s^-1]
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for (const auto& [species, deriv] : std::views::zip(m_networkSpecies, dydt_vec)) {
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massProductionRate += deriv * species.mass() * u;
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result.dydt[species] = deriv; // [mol][s^-1][g^-1]
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}
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result.nuclearEnergyGenerationRate = -massProductionRate * N_A * c * c; // [cm^2][s^-3] = [erg][s^-1][g^-1]
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return result;
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}
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template <IsArithmeticOrAD T>
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T GraphEngine::calculateMolarReactionFlow(
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const reaction::Reaction &reaction,
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const std::vector<T>& Y,
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const T T9,
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const T rho,
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const T Ye,
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const T mue,
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const std::function<std::optional<size_t>(const fourdst::atomic::Species &)>& speciesIDLookup
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) const {
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// --- Pre-setup (flags to control conditionals in an AD safe / branch aware manner) ---
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// ----- Constants for AD safe calculations ---
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const T zero = static_cast<T>(0.0);
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// --- Calculate the molar reaction rate (in units of [s^-1][cm^3(N-1)][mol^(1-N)] for N reactants) ---
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const T k_reaction = reaction.calculate_rate(T9, rho, Ye, mue, Y, m_indexToSpeciesMap);
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// --- Cound the number of each reactant species to account for species multiplicity ---
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std::unordered_map<fourdst::atomic::Species, int> reactant_counts;
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reactant_counts.reserve(reaction.reactants().size());
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for (const auto& reactant : reaction.reactants()) {
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reactant_counts[reactant] = reaction.countReactantOccurrences(reactant);
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}
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const int totalReactants = static_cast<int>(reaction.reactants().size());
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// --- Accumulator for the molar concentration ---
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auto molar_concentration_product = static_cast<T>(1.0);
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// --- Loop through each unique reactant species and calculate the molar concentration for that species then multiply that into the accumulator ---
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for (const auto& [species, count] : reactant_counts) {
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// --- Resolve species to molar abundance ---
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const std::optional<size_t> species_index = speciesIDLookup(species);
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if (!species_index.has_value()) {
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return static_cast<T>(0.0); // If any reactant is not present, the reaction cannot proceed
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}
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const T Yi = Y[species_index.value()];
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// --- If count is > 1 , we need to raise the molar concentration to the power of count since there are really count bodies in that reaction ---
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molar_concentration_product *= CppAD::pow(Yi, static_cast<T>(count)); // ni^count
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// --- Apply factorial correction for identical reactions ---
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if (count > 1) {
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molar_concentration_product /= static_cast<T>(std::tgamma(static_cast<double>(count + 1))); // Gamma function for factorial
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}
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}
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// --- Final reaction flow calculation [mol][s^-1][g^-1] ---
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// Note: If the threshold flag ever gets set to zero this will return zero.
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// This will result basically in multiple branches being written to the AD tape, which will make
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// the tape more expensive to record, but it will also mean that we only need to record it once for
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// the entire network.
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const T densityTerm = CppAD::pow(rho, totalReactants > 1 ? static_cast<T>(totalReactants - 1) : zero); // Density raised to the power of (N-1) for N reactants
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return molar_concentration_product * k_reaction * densityTerm;
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}
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};
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