133 lines
4.0 KiB
C
133 lines
4.0 KiB
C
/*BHEADER**********************************************************************
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* Copyright (c) 2007, Lawrence Livermore National Security, LLC.
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* Produced at the Lawrence Livermore National Laboratory.
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* Written by the HYPRE team. UCRL-CODE-222953.
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* All rights reserved.
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*
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* This file is part of HYPRE (see http://www.llnl.gov/CASC/hypre/).
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* Please see the COPYRIGHT_and_LICENSE file for the copyright notice,
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* disclaimer, contact information and the GNU Lesser General Public License.
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*
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* HYPRE is free software; you can redistribute it and/or modify it under the
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* terms of the GNU General Public License (as published by the Free Software
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* Foundation) version 2.1 dated February 1999.
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*
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* HYPRE is distributed in the hope that it will be useful, but WITHOUT ANY
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* WARRANTY; without even the IMPLIED WARRANTY OF MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the terms and conditions of the GNU General
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* Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* $Revision$
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***********************************************************************EHEADER*/
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/******************************************************************************
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*
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* This is an example of a C code illustrating the indentation used
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* for Hypre. This code does not illustrate issues related to
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* documentation, error handling, efficiency of implementation or
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* naming conventions.
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*
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* The most important item here is consistent indentation of the following
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* structures:
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* - for loops
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* - if statements
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*
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* Note that this code does something nonsensical - it is mainly for the
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* illustration of indentation.
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*
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*****************************************************************************/
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#include "headers.h"
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/*--------------------------------------------------------------------------
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* Matvec - matrix-vector function.
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*
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* Calculates y = alpha * A * x + beta * y
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* where A is a matrix stored in compressed sparse row format, x and y
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* are n vectors, and alpha and beta are scalars.
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*
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*--------------------------------------------------------------------------*/
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void
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Matvec( double alpha,
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Matrix *A,
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Vector *x,
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double beta,
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Vector *y )
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{
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double *a = MatrixData(A); /* element values for matrix A */
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int *ia = MatrixIA(A); /* pointer to start of each row */
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int *ja = MatrixJA(A); /* column values for matrix elements */
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int n = MatrixSize(A); /* size of matrix */
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double *xp = VectorData(x);
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double *yp = VectorData(y);
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double temp;
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int i, j, jj;
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/*-----------------------------------------------------------------------
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* Do (alpha == 0.0) computation
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*-----------------------------------------------------------------------*/
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if (alpha == 0.0)
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{
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for (i = 0; i < n; i++)
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yp[i] *= beta;
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return;
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}
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/*-----------------------------------------------------------------------
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* y = (beta/alpha)*y
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*-----------------------------------------------------------------------*/
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temp = beta / alpha;
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if (temp != 1.0)
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{
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if (temp == 0.0)
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{
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for (i = 0; i < n; i++)
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yp[i] = 0.0;
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}
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else
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{
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for (i = 0; i < n; i++)
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yp[i] *= temp;
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}
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}
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/*-----------------------------------------------------------------
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* y += A*x
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*-----------------------------------------------------------------*/
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for (i = 0; i < n; i++)
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{
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for (jj = ia[i]-1; jj < ia[i+1]-1; jj++)
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{
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j = ja[jj]-1;
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yp[i] += a[jj] * xp[j];
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}
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}
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/*-----------------------------------------------------------------
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* y = alpha*y
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*-----------------------------------------------------------------*/
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if (alpha != 1.0)
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{
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for (i = 0; i < n; i++)
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yp[i] *= alpha;
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}
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}
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