feat(libmeanfield): centrifugal + pressure

libmeanfield/interface/operators/prepared_hdiv_mass.cppm

@@ -0,0 +1,40 @@
+module;
+#include <cstdint>
+#include <memory>
+#include <mfem.hpp>
+
+export module mean_field:operators.prepared_hdiv_mass;
+export import :fem;
+export import :mapping.domain_mapper;
+
+export namespace mean_field::operators {
+    class PreparedMappedHDivMassOperator final : public mfem::Operator {
+    public:
+        PreparedMappedHDivMassOperator(
+            const fem::FEM &f,
+            const mapping::DomainMapperStateless &domain_mapper
+        );
+
+        void Prepare(const mfem::Vector &displacement_true);
+        void Mult(
+            const mfem::Vector &gravity_gradient_true,
+            mfem::Vector &action
+        ) const override;
+
+        [[nodiscard]] bool IsPrepared() const noexcept;
+        [[nodiscard]] std::uint64_t GetPreparationCount() const noexcept;
+
+    private:
+        const fem::FEM &m_fem;
+        const mapping::DomainMapperStateless &m_domain_mapper;
+
+        mfem::Array<int> m_stellar_marker;
+        mfem::Array<int> m_vacuum_marker;
+
+        std::unique_ptr<mfem::MatrixCoefficient> m_stellar_mass_coefficient;
+        std::unique_ptr<mfem::MatrixCoefficient> m_vacuum_mass_coefficient;
+        std::unique_ptr<mfem::ParBilinearForm> m_mass_form;
+        std::uint64_t m_preparation_count{0};
+        bool m_is_prepared{false};
+    };
+} // namespace mean_field::operators