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/*
This file is part of the FElt finite element analysis package.
Copyright (C) 1993-2000 Jason I. Gobat and Darren C. Atkinson
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/************************************************************************
*
* File: solvers.c
*
* Description:
*
************************************************************************/
# include <stdio.h>
# include <math.h>
# include <string.h>
# include "matrix.h"
int GaussSeidel(x, A, b)
Matrix x;
Matrix A;
Matrix b;
{
static int maxits = 5000;
static double tol = 0.0001;
int iter;
int i, j;
int n;
double sum1, sum2;
int converged;
double new_x;
double diff, base;;
if (!IsSquare(A))
return M_NOTSQUARE;
if (Mrows(b) != Mrows(A) || Mrows(x) != Mrows(A))
return M_SIZEMISMATCH;
if (!IsColumnVector(x) || !IsColumnVector(b))
return M_NOTCOLUMN;
n = Mrows(A);
for (i = 1 ; i <= n ; i++)
if (mdata(A,i,i) == 0.0)
return M_SINGULAR;
converged = 0;
for (iter = 1 ; iter <= maxits ; iter++) {
diff = 0.0;
base = 0.0;
for (i = 1 ; i <= n ; i++) {
sum1 = sum2 = 0.0;
for (j = 1 ; j <= i-1 ; j++)
sum1 += mdata(A,i,j)*mdata(x,j,1);
for (j = i+1 ; j <= n ; j++)
sum2 += mdata(A,i,j)*mdata(x,j,1);
new_x = (mdata(b,i,1) - sum1 - sum2) / mdata(A,i,i);
diff += (new_x - mdata(x,i,1))*(new_x - mdata(x,i,1));
base += new_x*new_x;
sdata(x, i, 1) = new_x;
}
if (base > 0 && diff/base < tol) {
converged = 1;
break;
}
}
if (!converged)
return M_NOTCONVERGED;
return 0;
}
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