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

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

}

void gausspv(float *a, float *b, int n)
{
	int i,j,k,il;
	float aux, aux2;
	for(i=0;i<n-1;i++)
	{
		aux=fabs(*(a + i*n + i));
		il=i;
		for(k = i+1; k < n; k++)
			if (aux<fabs(*(a + k*n + i)))
				{
				aux = fabs(*(a + k*n + i));
				il = k;
			};
		if (il != i)
			{
			for(j=i;j<n;j++)
				{
				aux = *(a + il*n + j);
				*(a + il*n + j) = *(a + i*n + j);
				*(a + i*n + j) = aux;
			}
			aux = *(b + il);
			*(b + il) = *(b + i);
			*(b + i) = aux;
		}
		aux = *(a + i*n + i);
		for(i=0;i<n-1;i++)
    {
        aux = *(a + i*n + i);
        for(k=i+1; k<n; k++)
            *(a + i*n + k) /= aux;
        *(b + i) /= aux;
        for(k=i+1;k<n;k++){
            aux2 = *(a + k*n + i);
            for(j=i+1;j<n;j++)
                *(a + k*n + j) -= aux2 * *(a + i*n + j);
            *(b + k) -= aux2 * *(b+i);
        }
    }
    *(b + n-1) /= *(a + n*n -1);
    for(i=n-2;i>=0;i--){
        aux= *(b + i);
        for(k=i+1;k<n;k++)
            aux -= *(a + i*n + k) * *(b + k);
        *(b + i) = aux;
    }
}


void main(){
		float a[16]={2.5,1.5,1.7,2.5,1.7,1.8,2.2,1.8,2.0,1.2,2.5,3.0,2.1,1.2,2.2,1.5};
    		float b[4]={11.11,10.67,12.41,10.52};
		float c[16]={21.0,130.0,0.0,2.1,13.0,80.0,4.74,752.0,0.0,-0.4,3.9816,4.2,0.0,0.0,1.7,0.9};
		float d[4]={153.1,849.74,7.7816,2.6};
		int mode_arrondi;
    int choix;
    printf("Choisissez le mode d'arrondi : \nFE_TOWARDZERO : 0\nFE_TONEAREST : 1\nFE_DOWNWARD : 2\nFE_UPWARD : 3\n");
    choix = scanf("%d",&mode_arrondi);
    switch (choix){
    case 0:
    fesetround(FE_TOWARDZERO);
    case 1:
    fesetround(FE_TONEAREST);
    case 2:
    fesetround(FE_DOWNWARD);
    case 3:
    fesetround(FE_UPWARD);
    }

		//test de la fonction avec pivot sur le cas de la première activité:
		gausspv(a,b,4);
		afficher_matrice(a,4,4);
		afficher_matrice(b,4,1);


}