perf(jacobian-action): major updates to jacobian action application by removing redudant quadrature work. ~5x increase in speed

libmeanfield/interface/equilibrium/stellar_discretization.cppm

@@ -0,0 +1,64 @@
+module;
+
+#include <memory>
+#include <stdexcept>
+
+export module mean_field:equilibrium.stellar_discretization;
+
+export import :fem;
+export import :mapping.domain_mapper;
+
+export namespace mean_field::equilibrium {
+    /*
+     * An explicit, non-owning view of the numerical discretization used by a
+     * stellar equilibrium problem. The referenced FEM and mapper must outlive
+     * every problem and structure that uses this view.
+     *
+     * Ownership cannot move here yet because FEM currently also contains
+     * mutable field workspaces. Separating those workspaces is a prerequisite
+     * for shared discretization ownership by solved Structure objects.
+     */
+    class StellarDiscretization final {
+    public:
+        explicit StellarDiscretization(fem::FEM &finiteElementModel)
+            : StellarDiscretization(
+                  finiteElementModel,
+                  RequireDomainMapper(finiteElementModel)
+              ) {
+        }
+
+        StellarDiscretization(
+            fem::FEM &finiteElementModel,
+            const mapping::DomainMapper &domainMapper
+        )
+            : m_finiteElementModel(std::addressof(finiteElementModel)),
+              m_domainMapper(std::addressof(domainMapper)) {
+            if (!finiteElementModel.okay()) {
+                throw std::invalid_argument("A stellar discretization requires a complete finite-element model.");
+            }
+        }
+
+        [[nodiscard]] fem::FEM &finiteElementModel() const noexcept {
+            return *m_finiteElementModel;
+        }
+
+        [[nodiscard]] const mapping::DomainMapper &domainMapper() const noexcept {
+            return *m_domainMapper;
+        }
+
+        [[nodiscard]] bool isCurrent() const noexcept {
+            return m_finiteElementModel != nullptr && m_domainMapper != nullptr && m_finiteElementModel->okay();
+        }
+
+    private:
+        [[nodiscard]] static const mapping::DomainMapper &RequireDomainMapper(const fem::FEM &finiteElementModel) {
+            if (finiteElementModel.domainMapperStateless == nullptr) {
+                throw std::invalid_argument("A stellar discretization requires a domain mapper.");
+            }
+            return *finiteElementModel.domainMapperStateless;
+        }
+
+        fem::FEM *m_finiteElementModel;
+        const mapping::DomainMapper *m_domainMapper;
+    };
+} // namespace mean_field::equilibrium