From 36849783f5a9a10d4e5b92f8c7f20671bea165fa Mon Sep 17 00:00:00 2001
From: Emily Boudreaux <thomas@boudreauxmail.com>
Date: Wed, 22 Oct 2025 10:12:59 -0400
Subject: [PATCH] perf(CompositionEntry): made symbol and isotope std::optional
 for comopsition entry so that construction can be cheaper

---
 .../include/fourdst/composition/composition.h |  5 +++--
 src/composition/lib/composition.cpp           | 21 ++++++++-----------
 2 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/src/composition/include/fourdst/composition/composition.h b/src/composition/include/fourdst/composition/composition.h
index 5ffdaa6..0be32ea 100644
--- a/src/composition/include/fourdst/composition/composition.h
+++ b/src/composition/include/fourdst/composition/composition.h
@@ -25,6 +25,7 @@
 #include <set>
 
 #include <utility>
+#include <optional>
 
 #include "fourdst/config/config.h"
 #include "fourdst/logging/logging.h"
@@ -82,8 +83,8 @@ namespace fourdst::composition {
      * fraction or number fraction). It manages the state and conversions for that single entry.
      */
     struct CompositionEntry {
-        std::string m_symbol; ///< The chemical symbol of the species (e.g., "H-1", "Fe-56").
-        atomic::Species m_isotope; ///< The `atomic::Species` object containing detailed isotope data.
+        std::optional<std::string> m_symbol = std::nullopt; ///< The chemical symbol of the species (e.g., "H-1", "Fe-56").
+        std::optional<atomic::Species> m_isotope = std::nullopt; ///< The `atomic::Species` object containing detailed isotope data.
         bool m_massFracMode = true; ///< The mode of the composition entry. True if mass fraction, false if number fraction.
 
         double m_massFraction = 0.0; ///< The mass fraction of the species. Valid only if `m_massFracMode` is true.
diff --git a/src/composition/lib/composition.cpp b/src/composition/lib/composition.cpp
index 396f144..79c5956 100644
--- a/src/composition/lib/composition.cpp
+++ b/src/composition/lib/composition.cpp
@@ -66,10 +66,7 @@ namespace {
 
 namespace fourdst::composition {
 
-    CompositionEntry::CompositionEntry() :
-    m_symbol("H-1"),
-    m_isotope(fourdst::atomic::species.at("H-1")),
-    m_initialized(false) {}
+    CompositionEntry::CompositionEntry() = default;
 
     CompositionEntry::CompositionEntry(
         const std::string& symbol,
@@ -96,7 +93,7 @@ namespace fourdst::composition {
     }
 
     std::string CompositionEntry::symbol() const {
-        return m_symbol;
+        return m_symbol.value();
     }
 
     double CompositionEntry::mass_fraction() const {
@@ -104,7 +101,7 @@ namespace fourdst::composition {
             throw exceptions::CompositionModeError("Composition entry is in number fraction mode.");
         }
         // X_i = (moles_i / mass_total) * (mass_i / moles_i) = m_molesPerMass * A_i
-        return m_molesPerMass * m_isotope.mass();
+        return m_molesPerMass * m_isotope->mass();
     }
 
     double CompositionEntry::number_fraction() const {
@@ -128,7 +125,7 @@ namespace fourdst::composition {
     }
 
     atomic::Species CompositionEntry::isotope() const {
-        return m_isotope;
+        return m_isotope.value();
     }
 
     void CompositionEntry::setMassFraction(
@@ -138,10 +135,10 @@ namespace fourdst::composition {
             throw exceptions::CompositionModeError("Composition entry is in number fraction mode.");
         }
         // Set the invariant from the given mass fraction
-        if (m_isotope.mass() == 0.0) {
+        if (m_isotope->mass() == 0.0) {
              m_molesPerMass = 0.0;
         } else {
-             m_molesPerMass = mass_fraction / m_isotope.mass();
+             m_molesPerMass = mass_fraction / m_isotope->mass();
         }
     }
 
@@ -705,7 +702,7 @@ namespace fourdst::composition {
 
         for (const auto &val: m_compositions | std::views::values) {
             // Sum of (X_i * Z_i / A_i)
-            zSum += (val.mass_fraction() * val.m_isotope.z())/val.m_isotope.a();
+            zSum += (val.mass_fraction() * val.m_isotope->z())/val.m_isotope->a();
         }
 
         // <Z> = <A> * sum(X_i * Z_i / A_i)
@@ -725,7 +722,7 @@ namespace fourdst::composition {
 
         double Ye = 0.0;
         for (const auto &val: m_compositions | std::views::values) {
-            Ye += (val.mass_fraction() * val.m_isotope.z())/val.m_isotope.a();
+            Ye += (val.mass_fraction() * val.m_isotope->z())/val.m_isotope->a();
         }
         m_cache.Ye = Ye;
         return Ye;
@@ -1071,7 +1068,7 @@ namespace fourdst::composition {
         std::ostream& os,
         const CompositionEntry& entry
     ) {
-        os << "<" << entry.m_symbol << " : m_frac = " << entry.mass_fraction() << ">";
+        os << "<" << entry.m_symbol.value() << " : m_frac = " << entry.mass_fraction() << ">";
         return os;
     }