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MathNetInterop

Converts between CsrMatrix and Math.NET Numerics' sparse matrix.

public static class MathNetInterop

Example — a matrix out of Lodestar, into Math.NET, and back.

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

var matrix = new CsrMatrix(
    rowCount: 2,
    columnCount: 3,
    values: [1.0, 2.0, 3.0],
    columnIndices: [0, 2, 1],
    rowPointers: [0, 2, 3]);

SparseMatrix sparse = MathNetInterop.ToSparseMatrix(matrix);
double corner = sparse[0, 2];              // => 2

CsrMatrix back = MathNetInterop.ToCsrMatrix(sparse);
int stored = back.NonZeroCount;            // => 3

Remarks — the two sides agree on the layout, so a compressed-row matrix moves as three arrays rather than rows × columns cells; a dense or diagonal Math.NET matrix is walked over what it stores. Neither result shares an array with its source: Math.NET's storage is mutable through At, and a shared buffer would let a write on one matrix move the other.

One asymmetry is worth knowing. CsrMatrix validates four things — the row pointers start at zero, do not decrease, end at the stored count, and every column index is in range — and says nothing about the order of column indices within a row, about explicit zeros, or about a column appearing twice. Math.NET reaches a cell by searching the row, which assumes the order. Its own compressed-row factory sorts each row of its copy and adds duplicate columns, but with a sort that is unstable past 16 entries, so MathNetInterop.ToSparseMatrix bypasses it: a matrix with strictly increasing rows is copied as it is, and any other sorted here first, a repeated column added in stored order as CsrMatrix.ToDense does (#1548).

Applies to — net10.0, netstandard2.0.

See also — the matrix conversion index, sparse matrices, matrix factorization.

Members

Member	What it does
MathNetInterop.ToCsrMatrix	Converts a Math.NET matrix into a CsrMatrix.
MathNetInterop.ToSparseMatrix	Converts a CsrMatrix into a Math.NET SparseMatrix.