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#2
沈和2020-09-05 17:10
在站内找到了运行更快的。是把矩阵先化成上三角形式，再进行求值的。
https://bbs.bccn.net/thread-292421-1-1.html  程序代码：#include "stdio.h" #include <math.h> #include <stdlib.h> int main(void) { int size_n = 7; double matrix[size_n][size_n]; srand(0); for (int i = 0; i < size_n; ++i) for (int j = 0; j < size_n; ++j) { matrix[i][j] = 0.03 * (rand() % 51 + 19); } double r2z; int i, j, z; for (i = 0; i < size_n - 1; i++) { for (j = i; j < size_n - 1; j++) { if (matrix[i][i] == 0) for (j = i; matrix[i][i] == 0; j++) { for (z = 0; z < size_n; z++) matrix[i][z] = matrix[i][z] + matrix[j + 1][z]; if (matrix[i][i] != 0) break; } r2z = -matrix[j + 1][i] / matrix[i][i]; for (z = i; z < size_n; z++) matrix[j + 1][z] = r2z * (matrix[i][z]) + matrix[j + 1][z]; } } double res = 1.0; for (i = 0; i < size_n; i++) res = res * (matrix[i][i]); for (int m = 0; m < size_n; ++m) { for (int n=0; n< size_n;++n) { printf("%4.1lf,", matrix[m][n]); } printf("\n"); } printf("%lf\n", res); } [此贴子已经被作者于2020-9-5 18:14编辑过] |
n取11以及以下时，运行时间挺短的。n取12时，运行时间是1分钟。n取13时，要12分钟。
det.h
程序代码：#ifndef DET_H
#define DET_H
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
double det(double *matrix, unsigned size_n);
#endif
det.c
程序代码：#include "det.h"
double det(double *matrix, unsigned size_n) {
if (size_n == 1)
return *matrix;
else {
double sum = 0.0;
double *slice = malloc(sizeof(double) * pow(size_n - 1, 2));
for (int i = 0; i < size_n; ++i) {
int cnt = 0;
for (int j = 1; j < size_n; ++j) {
for (int k = 0; k < size_n; ++k) {
if (i != k) {
slice[cnt++] = matrix[j * size_n + k];
}
}
}
sum += pow(-1, i) * det(slice, size_n - 1) * matrix[i];
}
free(slice);
return sum;
}
}
1.c
程序代码：#include "det.h"
#include <stdio.h>
int main(void) {
double a[1] = {1};
printf("%lf\n", det(a, 1));
double b[4] = {1, 2, 3, 4};
printf("%lf\n", det(b, 2));
double c[9] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
printf("%lf\n", det(c, 3));
unsigned n = 12;
double *d = malloc(sizeof(double) * pow(n, 2));
srand(0);
for (int i = 0; i < pow(n, 2); ++i) {
d[i] = 0.03*(rand() % 51 + 19);
}
printf("%lf\n", det(d, n));
// getchar();
return 0;
}