feat(mean_field): added initial implementation

note this implementation lacks many tests

libmeanfield/interface/mapping/coefficients.cppm

@@ -0,0 +1,95 @@
+module;
+#include "mean_field.h"
+
+export module mean_field:mapping.coefficients;
+export import :mapping.domain_mapper;
+export import :mapping.types;
+
+export namespace mean_field::mapping {
+    class MappedScalarCoefficient : public mfem::Coefficient {
+    public:
+        MappedScalarCoefficient(
+            const DomainMapper &map,
+            mfem::Coefficient &coeff,
+            COORDINATE_SPACE coord_space = COORDINATE_SPACE::PHYSICAL
+        );
+
+        double Eval(
+            mfem::ElementTransformation &T,
+            const mfem::IntegrationPoint &ip
+        ) override;
+
+    private:
+        static double eval_at_point(
+            mfem::Coefficient &c,
+            mfem::ElementTransformation &T,
+            const mfem::IntegrationPoint &ip
+        );
+
+    private:
+        const DomainMapper &m_map;
+        mfem::Coefficient &m_coeff;
+        COORDINATE_SPACE m_coord_space;
+    };
+
+    class MappedDiffusionCoefficient : public mfem::MatrixCoefficient {
+    public:
+        MappedDiffusionCoefficient(
+            const DomainMapper &map,
+            mfem::Coefficient &sigma,
+            int dim
+        );
+
+        MappedDiffusionCoefficient(
+            const DomainMapper &map,
+            mfem::MatrixCoefficient &sigma
+        );
+
+        void Eval(mfem::DenseMatrix &K, mfem::ElementTransformation &T, const mfem::IntegrationPoint &ip) override;
+
+    private:
+        const DomainMapper &m_map;
+        mfem::Coefficient *m_scalar;
+        mfem::MatrixCoefficient *m_tensor;
+    };
+
+    class MappedVectorCoefficient : public mfem::VectorCoefficient {
+    public:
+        MappedVectorCoefficient(
+            const DomainMapper &map,
+            mfem::VectorCoefficient &coeff
+        );
+
+        void Eval(mfem::Vector &V, mfem::ElementTransformation &T, const mfem::IntegrationPoint &ip) override;
+
+    private:
+        const DomainMapper &m_map;
+        mfem::VectorCoefficient &m_coeff;
+    };
+
+    class PhysicalPositionFunctionCoefficient : public mfem::Coefficient {
+    public:
+        using Func = std::function<double(const mfem::Vector &x)>;
+
+        PhysicalPositionFunctionCoefficient(
+            const DomainMapper &map,
+            Func f
+        );
+
+        double Eval(mfem::ElementTransformation &T, const mfem::IntegrationPoint &ip) override;
+
+    private:
+        Func m_f;
+        const DomainMapper &m_map;
+    };
+
+    class MappedHDivMassCoefficient final : public mfem::MatrixCoefficient {
+    public:
+        MappedHDivMassCoefficient(const DomainMapper& map, const int dim);
+
+        void Eval(mfem::DenseMatrix& matrix, mfem::ElementTransformation& transformation, const mfem::IntegrationPoint& integration_point) override;
+    private:
+        const DomainMapper& m_map;
+
+    };
+}