cholesky.c

cholesky.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

void cholesky(float* m, int n) {
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < i; j++) {
            float sum = 0;
            for (int k = 0; k < j; k++) {
                sum += m[i * n + k] * m[j * n + k];
            }
            m[i * n + j] = (m[i * n + j] - sum) / m[j * n + j];
        }
        
        float sum = 0;
        for (int j = 0; j < i; j++) {
            float f = m[i * n + j];
            sum += f * f;
        }
        m[i * n + i] = sqrtf(m[i * n + i] - sum);
    }
}

void print_matrix(float* m, int n) {
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            printf("%f ", m[i * n + j]);
        }
        printf("\n");
    }
    printf("\n");
}

int main(int argc, char** argv) {
    int n;
    scanf("%d", &n);

    float* m = malloc(n * n * sizeof(float));

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            float x;
            scanf("%f", &x);
            m[i * n + j] = x;
        }
    }

    cholesky(m, n);
    print_matrix(m, n);

    free(m);
}