#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#define Num 5
void mprint(double A[Num][Num], double B[Num]);
time_t t1;
int main()
{
int i,j,k;
int o_row,n_row;
double A[Num][Num];
double A2[Num][Num];
double B[Num];
double B2[Num];
double pivot;
double temp;
double ans[Num];
srand(time(&t1));
for (i=0;i<Num;i++)
{
B[i] = rand()/32767.0;
B2[i]= B[i];
for (j=0;j<Num;j++)
{
A[i][j] = rand()/32767.0;
A2[i][j] = A[i][j];
}
}
printf("The matrix is now as following:\n");
mprint(A,B);
for (i=0;i<Num-1;i++)
{
pivot = fabs(A[i][i]);
o_row = i;
n_row = i;
for (j=i+1;j<Num;j++)
{
if (fabs(A[j][i])>=pivot)
{
pivot = fabs(A[j][i]);
n_row = j;
}
}
if (o_row != n_row)
{
for (k=0;k<Num;k++)
{
temp = A[o_row][k];
A[o_row][k] = A[n_row][k];
A[n_row][k] = temp;
}
temp = B[o_row];
B[o_row] = B[n_row];
B[n_row] = temp;
}
printf("The matrix is now as following:\n");
mprint(A,B);
for (j=i+1;j<Num;j++)
{
temp = A[j][i]/A[i][i];
for (k=0;k<Num;k++) A[j][k] = A[j][k] - A[i][k]*temp;
B[j]= B[j]-B[i]*temp;
}
printf("The matrix is now as following:\n");
mprint(A,B);
system("pause");
}
ans[Num-1] = B[Num-1]/A[Num-1][Num-1];
for (i=Num-2;i>=0;i--)
{
ans[i]=B[i];
for ( j=Num-1;j>i;j--) ans[i]-=A[i][j]*ans[j];
ans[i] = ans[i]/A[i][i];
}
for (i =0;i<Num;i++) printf("x[%d]= %lf\n",i+1,ans[i]);
for (i=0;i<Num;i++)
{
temp = 0;
for (j=0;j<Num;j++) temp+=A2[i][j]*ans[j];
printf("%dth:old value = %lf, new value =%lf\n",i+1,B2[i],temp);
}
return 0;
}
void mprint(double A[Num][Num], double B[Num])
{
int i,j;
for (i=0;i<Num;i++)
{
for (j=0;j<Num-1;j++) printf("%lf ",A[i][j]);
printf("%lf | ",A[i][Num-1]);
printf("%lf\n",B[i]);
}
}
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