Commit d3b482aa authored by Matthias Braun's avatar Matthias Braun
Browse files

gaussjordan: Cleanup

parent 7863c88e
......@@ -15,13 +15,14 @@
*/
/**
* solves a system of linear equations and returns 0 if successful
* Solves a system of linear equations.
*
* @param A the linear equations as matrix
* @param b the result vector, will contain the result if successful
* @param nsize the size of the equation system
* @param matrix the linear equations as matrix (square matrix, \t n x \p n)
* @param result the result vector, will contain the result if successful
* @param n the size of the equation system
* @returns 0 if successful, -1 if ill-conditioned matrix
*/
FIRM_API int firm_gaussjordansolve(double *A, double *b, int nsize);
FIRM_API int firm_gaussjordansolve(double *matrix, double *result, unsigned n);
/** @} */
......
......@@ -24,43 +24,37 @@
/* Inverse Theory--1984 p210 ), but performs actual */
/* row switching to simplify the programming. */
/* Partial pivoting is used. */
/* */
/* A[][] is a square matrix, N x N */
/* vec[] is N x 1 of the matrix */
/* nsize is the size of the equation system */
/* */
/* returns 0 if successful */
/* returns -1 if ill-conditioned matrix */
/*------------------------------------------------------*/
#include "gaussjordan.h"
#include <math.h>
#include <stdlib.h>
#include "xmalloc.h"
#include "gaussjordan.h"
#define SMALL 0.00001
int firm_gaussjordansolve(double *A, double *vec, int nsize)
int firm_gaussjordansolve(double *A, double *vec, unsigned nsize)
{
int i, j, row, col, col2, biggest_r = 0, biggest_c = 0, t;
double big, temp, sum;
double *scramvec = XMALLOCN(double, nsize);
int *x = XMALLOCN(int, nsize);
unsigned *x = XMALLOCN(unsigned, nsize);
int res = 0;
#define _A(row,col) A[(row)*nsize + (col)]
/* init x[] */
for (i = 0; i < nsize; ++i)
for (unsigned i = 0; i < nsize; ++i) {
x[i] = i;
}
/* triangularize A */
/* ie A has zeros below its diagonal */
for (col = 0; col < nsize - 1; ++col) {
big = 0;
unsigned biggest_r = 0;
unsigned biggest_c = 0;
for (unsigned col = 0; col < nsize - 1; ++col) {
double big = 0;
/* find the largest left in LRH box */
for (row = col; row < nsize; ++row) {
for (col2 = col; col2 < nsize; ++col2) {
temp = fabs(_A(row,col2));
for (unsigned row = col; row < nsize; ++row) {
for (unsigned col2 = col; col2 < nsize; ++col2) {
double temp = fabs(_A(row,col2));
if (temp > big) {
biggest_r = row;
biggest_c = col2;
......@@ -74,36 +68,35 @@ int firm_gaussjordansolve(double *A, double *vec, int nsize)
}
/* swap rows */
for (i=0;i<nsize;i++) {
temp = _A(col,i);
for (unsigned i = 0; i < nsize; ++i) {
double temp = _A(col,i);
_A(col,i) = _A(biggest_r,i);
_A(biggest_r,i) = temp;
}
/* swap vec elements */
temp = vec[col];
double temp = vec[col];
vec[col] = vec[biggest_r];
vec[biggest_r] = temp;
/* swap columns */
for (i=0;i<nsize;i++) {
temp = _A(i,col);
for (unsigned i = 0; i < nsize; ++i) {
double temp = _A(i,col);
_A(i,col) = _A(i,biggest_c);
_A(i,biggest_c) = temp;
}
/* swap unknowns */
t = x[col];
unsigned t = x[col];
x[col] = x[biggest_c];
x[biggest_c] = t;
/* partially annihilate this col */
/* zero columns below diag */
for (row=col+1;row<nsize;row++) {
for (unsigned row = col+1; row < nsize; ++row) {
/* changes during calc */
temp = _A(row,col) / _A(col,col);
double temp = _A(row,col) / _A(col,col);
/* annihilates A[][] */
for (i=col;i<nsize;i++)
for (unsigned i = col; i < nsize; ++i)
_A(row,i) = _A(row,i) - temp * _A(col,i);
/* same op on vec */
......@@ -115,15 +108,15 @@ int firm_gaussjordansolve(double *A, double *vec, int nsize)
scramvec[nsize - 1] = vec[nsize - 1] / _A(nsize - 1,nsize - 1);
/* answer needs sorting */
for (i=nsize-2;i>=0;i--) {
sum = 0;
for (j=i+1;j<nsize;j++)
sum = sum + _A(i,j) * scramvec[j];
for (unsigned i = nsize - 1; i-- > 0;) {
int sum = 0;
for (unsigned j = i+1; j < nsize; ++j)
sum += _A(i,j) * scramvec[j];
scramvec[i] = (vec[i] - sum) / _A(i,i);
}
/* reorder unknowns--return in vec */
for (i=0;i<nsize;i++) {
j = x[i];
for (unsigned i = 0; i < nsize; ++i) {
unsigned j = x[i];
vec[j] = scramvec[i];
}
......
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