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gauss.c
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gauss.c
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/***********************************************************
gauss.c -- Gauss (ガウス) 法
***********************************************************/
#include "matutil.c"
void gauss(int n, matrix a)
{
int i, j, k;
double t;
for (k = 0; k < n - 1; k++) {
for (i = k + 1; i < n; i++) {
t = a[i][k] / a[k][k];
for (j = k + 1; j <= n; j++)
a[i][j] -= t * a[k][j];
}
}
for (i = n - 1; i >= 0; i--) {
t = a[i][n];
for (j = i + 1; j < n; j++) t -= a[i][j] * a[j][n];
a[i][n] = t / a[i][i];
}
}
#include <limits.h>
double rnd(void) /* 乱数 0 < rnd() < 1 */
{
static unsigned long seed = 123456789UL; /* 奇数 */
return (seed *= 69069UL) / (ULONG_MAX + 1.0);
}
int main(void)
{
int i, j, n;
matrix a, b;
double s;
printf("n = "); scanf("%d", &n);
a = new_matrix(n, n + 1);
b = new_matrix(n, n + 1);
for (i = 0; i < n; i++)
for (j = 0; j < n; j++)
a[i][j] = b[i][j] = rnd() - rnd();
for (i = 0; i < n; i++)
a[i][n] = b[i][n] = rnd() - rnd();
printf("係数行列 (右辺も含む)\n");
matprint(a, n + 1, 10, "%7.3f");
gauss(n, a);
printf("解と, 解を代入したときの両辺の差\n");
for (i = 0; i < n; i++) {
s = b[i][n];
for (j = 0; j < n; j++) s -= b[i][j] * a[j][n];
printf("%4d: %12.7f %12.7f\n", i, a[i][n], s);
}
return 0;
}