/// <summary>
/// Sparse matrix multiplication, C = A*B
/// </summary>
/// <param name="other">column-compressed matrix</param>
/// <returns>C = A*B, null on error</returns>
public override CompressedColumnStorage <double> Multiply(CompressedColumnStorage <double> other)
{
if (other == null)
{
throw new ArgumentNullException(nameof(other));
}
int p, j, nz = 0;
int[] cp, ci;
double[] cx;
int m = this.rowCount;
int n = other.ColumnCount;
int anz = this.NonZerosCount;
int bnz = other.NonZerosCount;
if (this.ColumnCount != other.RowCount)
{
throw new ArgumentException(Resources.MatrixDimensions);
}
if ((m > 0 && this.ColumnCount == 0) || (other.RowCount == 0 && n > 0))
{
throw new Exception(Resources.InvalidDimensions);
}
var bp = other.ColumnPointers;
var bi = other.RowIndices;
var bx = other.Values;
// Workspace
var w = new int[m];
var x = new double[m];
var result = new SparseMatrix(m, n, anz + bnz);
cp = result.ColumnPointers;
for (j = 0; j < n; j++)
{
if (nz + m > result.Values.Length)
{
// Might throw out of memory exception.
result.Resize(2 * (result.Values.Length) + m);
}
ci = result.RowIndices;
cx = result.Values; // C.i and C.x may be reallocated
cp[j] = nz; // column j of C starts here
for (p = bp[j]; p < bp[j + 1]; p++)
{
nz = this.Scatter(bi[p], bx[p], w, x, j + 1, result, nz);
}
for (p = cp[j]; p < nz; p++)
{
cx[p] = x[ci[p]];
}
}
cp[n] = nz; // finalize the last column of C
result.Resize(0); // remove extra space from C
result.SortIndices();
return(result); // success
}