sparsityPattern.hpp

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// SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: 2025 NeoN authors
 
#pragma once
 
#include "NeoN/mesh/unstructured/unstructuredMesh.hpp"
// #include "NeoN/linearAlgebra/linearSystem.hpp"
 
namespace NeoN::finiteVolume::cellCentred
{
 
/* @class SparsityPattern
 * @brief row and column index representation of a mesh
 *
 * This class implements the finite volume 3/5/7 pt stencil specific generation
 * of sparsity patterns from a given unstructured mesh
 *
 */
class SparsityPattern
{
public:
 
    // TODO implement ctor copying all members
    SparsityPattern(const UnstructuredMesh& mesh);
 
    void update();
 
    // TODO: rename upperOffset
    const Vector<uint8_t>& ownerOffset() const;
 
    // TODO: rename lowerOffset
    const Vector<uint8_t>& neighbourOffset() const;
 
    const Vector<uint8_t>& diagOffset() const;
 
    const UnstructuredMesh& mesh() const { return mesh_; };
 
    [[nodiscard]] const Vector<localIdx>& colIdxs() const { return colIdxs_; };
 
    [[nodiscard]] const Vector<localIdx>& rowPtrs() const { return rowPtrs_; };
 
    [[nodiscard]] localIdx rows() const { return diagOffset_.size(); };
 
    [[nodiscard]] localIdx nnz() const { return colIdxs_.size(); };
 
    // add selection mechanism via dictionary later
    static const std::shared_ptr<SparsityPattern> readOrCreate(const UnstructuredMesh& mesh);
 
private:
 
    const UnstructuredMesh& mesh_;
 
    Vector<localIdx> rowPtrs_; 
 
    Vector<localIdx> colIdxs_; 
 
    Vector<uint8_t> ownerOffset_; 
 
    Vector<uint8_t> neighbourOffset_; 
 
    Vector<uint8_t> diagOffset_; 
};
 
} // namespace NeoN::finiteVolume::cellCentred