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Converts a Math.NET matrix into a CsrMatrix.

public static CsrMatrix ToCsrMatrix(Matrix<double> matrix)

Parameters — matrix is the matrix to convert; sparse or dense.

Returns — a CsrMatrix of the same shape holding the same values, sharing no array with the source.

Exceptions — ArgumentNullException when matrix is null.

Example — a dense matrix keeps only what it actually stores.

using Lodestar.Abstractions;
using Lodestar.Extensions.MathNet;
using MathNet.Numerics.LinearAlgebra;
using MathNet.Numerics.LinearAlgebra.Double;

Matrix<double> dense = DenseMatrix.OfRowArrays(
    [0.0, 3.0, 0.0],
    [0.0, 0.0, 0.0],
    [4.0, 0.0, 5.0]);

CsrMatrix csr = MathNetInterop.ToCsrMatrix(dense);

int stored = csr.NonZeroCount;   // => 3
int rows = csr.RowCount;         // => 3

Remarks — a matrix already in compressed-row form hands over its three arrays, copied so neither side can mutate the other's. Any other storage is walked. A dense matrix, or a compressed-column one, has none of the arrays the fast path copies, so its cells are visited row by row and the non-zero ones collected — the honest cost of changing layout, not a defect of this path. A caller converting a large dense matrix is paying for the layout change and should expect to.

An empty row is a row: it contributes no stored value and its row pointer repeats the previous one, which is what the example's middle row shows.

Applies to — net10.0, netstandard2.0.

See also — MathNetInterop, MathNetInterop.ToSparseMatrix.