scscmv.c

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//       Ifpack: Object-Oriented Algebraic Preconditioner Package
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void  scscmv (int isym, int indexbase, int m, int n, 
        double *val, int *indx, int *pntr, 
        double *x, double *y)
{
    int i, j, jbgn, jend;
 
 
/*     Performs the matrix-vector operation
 
                      y = A*x 
 
       where x and y are vectors and A is a sparse matrix stored
       in (Harwell-Boeing) compress column format. */
 
/*     -------------------------- 
       First executable statement 
       -------------------------- */
 
/* .....initialize soln */
 
    for (i = 0; i < m; i++)
  y[i] = 0.0;
 
/* .....do a series of SPAXPYs (sparse saxpys) */
 
    for (j = 0; j <n ; j++) 
      {
  jbgn = pntr[j]-indexbase;
  jend = pntr[j + 1]-indexbase;
 
  for (i = jbgn; i < jend; i++)
    {
      y[indx[i]-indexbase] += val[i] * x[j];
      if (indx[i]-indexbase != j && isym) y[j] += val[i]*x[indx[i]-indexbase];
    }
      }
 
    return;
} /* scscmv */