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scscmv.c
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00001 /*@HEADER
00002 // ***********************************************************************
00003 // 
00004 //       Ifpack: Object-Oriented Algebraic Preconditioner Package
00005 //                 Copyright (2002) Sandia Corporation
00006 // 
00007 // Under terms of Contract DE-AC04-94AL85000, there is a non-exclusive
00008 // license for use of this work by or on behalf of the U.S. Government.
00009 // 
00010 // This library is free software; you can redistribute it and/or modify
00011 // it under the terms of the GNU Lesser General Public License as
00012 // published by the Free Software Foundation; either version 2.1 of the
00013 // License, or (at your option) any later version.
00014 //  
00015 // This library is distributed in the hope that it will be useful, but
00016 // WITHOUT ANY WARRANTY; without even the implied warranty of
00017 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00018 // Lesser General Public License for more details.
00019 //  
00020 // You should have received a copy of the GNU Lesser General Public
00021 // License along with this library; if not, write to the Free Software
00022 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
00023 // USA
00024 // Questions? Contact Michael A. Heroux (maherou@sandia.gov) 
00025 // 
00026 // ***********************************************************************
00027 //@HEADER
00028 */
00029 
00030 void  scscmv (int isym, int indexbase, int m, int n, 
00031         double *val, int *indx, int *pntr, 
00032         double *x, double *y)
00033 {
00034     int i, j, jbgn, jend;
00035 
00036 
00037 /*     Performs the matrix-vector operation
00038 
00039                       y = A*x 
00040 
00041        where x and y are vectors and A is a sparse matrix stored
00042        in (Harwell-Boeing) compress column format. */
00043 
00044 /*     -------------------------- 
00045        First executable statement 
00046        -------------------------- */
00047 
00048 /* .....initialize soln */
00049 
00050     for (i = 0; i < m; i++)
00051   y[i] = 0.0;
00052 
00053 /* .....do a series of SPAXPYs (sparse saxpys) */
00054 
00055     for (j = 0; j <n ; j++) 
00056       {
00057   jbgn = pntr[j]-indexbase;
00058   jend = pntr[j + 1]-indexbase;
00059 
00060   for (i = jbgn; i < jend; i++)
00061     {
00062       y[indx[i]-indexbase] += val[i] * x[j];
00063       if (indx[i]-indexbase != j && isym) y[j] += val[i]*x[indx[i]-indexbase];
00064     }
00065       }
00066 
00067     return;
00068 } /* scscmv */
00069 
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