SparseCompRow.c

/* multiple iterations used to make kernel have roughly same granulairty as
 * other Scimark kernels.
 */
double SparseCompRow_num_flops(int N, int nz, int num_iterations)
{
    /* Note that if nz does not divide N evenly, then the actual number of
     * nonzeros used is adjusted slightly.
     */
    int actual_nz = (nz / N) * N;
    return ((double) actual_nz) * 2.0 * ((double) num_iterations);
}

/* computes  a matrix-vector multiply with a sparse matrix held in compress-row
 * format.  If the size of the matrix in MxN with nz nonzeros, then the val[]
 * is the nz nonzeros, with its ith entry in column col[i]. The integer vector
 * row[] is of size M+1 and row[i] points to the begining of the ith row in
 * col[].
 */
void SparseCompRow_matmult(int M,
                           double *y,
                           const double *val,
                           const int *row,
                           const int *col,
                           const double *x,
                           int NUM_ITERATIONS)
{
    for (int reps = 0; reps < NUM_ITERATIONS; reps++) {
        for (int r = 0; r < M; r++) {
            double sum = 0.0;
            int rowR = row[r];
            int rowRp1 = row[r + 1];
            for (int i = rowR; i < rowRp1; i++)
                sum += x[col[i]] * val[i];
            y[r] = sum;
        }
    }
}