implementation of csr_todense

csr.h

/*
 * Compute B += A for CSR matrix A, C-contiguous dense matrix B
 *
 * Input Arguments:
 *   I  n_row           - number of rows in A
 *   I  n_col           - number of columns in A
 *   I  Ap[n_row+1]     - row pointer
 *   I  Aj[nnz(A)]      - column indices
 *   T  Ax[nnz(A)]      - nonzero values
 *   T  Bx[n_row*n_col] - dense matrix in row-major order
 *
 */
template <class I, class T>
void csr_todense(const I n_row,
                 const I n_col,
                 const I Ap[],
                 const I Aj[],
                 const T Ax[],
                       T Bx[])
{
    T * Bx_row = Bx;
    for(I i = 0; i < n_row; i++){
        for(I jj = Ap[i]; jj < Ap[i+1]; jj++){
            Bx_row[Aj[jj]] += Ax[jj];
        }
        Bx_row += (npy_intp)n_col;
    }
}