Gpu devicesparsematrix upload

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DeviceSparseMatrix.Upload

Uploads a CSR matrix to the accelerator.

public static DeviceSparseMatrix Upload(GpuContext context, ReadOnlySpan<int> rowPointers, ReadOnlySpan<int> columnIndices, ReadOnlySpan<double> values, int rowCount, int columnCount)

Parameters — context is the accelerator to upload to. rowPointers holds rowCount + 1 offsets into the other two. columnIndices holds one column per stored value, ascending inside a row. values holds the stored values in the same order. rowCount and columnCount are the matrix's shape; columnCount is not derived from the indices, because a matrix may have trailing columns no row stores anything in.

Returns — DeviceSparseMatrix, owning three device buffers the caller disposes.

Exceptions — ArgumentNullException when context is null; ArgumentOutOfRangeException when a dimension is below 1; ArgumentException when the three arrays do not describe one CSR matrix — rowPointers not starting at 0, decreasing, or ending anywhere but at the value count, or a column index outside [0, columnCount).

Example — the shape a caller writes.

using Lodestar.Gpu.Compute;

using var context = GpuContext.Create(preferCpu: true);
using var matrix = DeviceSparseMatrix.Upload(
    context, [0, 2, 3], [0, 1, 1], [1.0, 2.0, 3.0], rowCount: 2, columnCount: 2);

int stored = matrix.NonZeroCount;  // => 3

Remarks — the shapes and the structure are checked because each has its own failure. rowPointers of the wrong length silently shifts every row; columnIndices and values of different lengths reads past one of them; and a final offset that disagrees with the value count means the last row is truncated without anything noticing. The kernel indexes device memory with the offsets and the columns unchecked, so a first offset past 0 drops stored values, and an offset that steps back or a column outside the matrix reads another buffer (#898). The structure is checked in one pass per array, once per upload.

Column indices ascending inside a row is a precondition, not a check. The kernel relies on it only to read contiguous memory, so an unsorted row produces the same arithmetic more slowly rather than a wrong answer — but it is what CsrMatrix guarantees and what a caller building the arrays by hand has to preserve.

Applies to — net10.0, netstandard2.1.

See also — DeviceSparseMatrix.