Check Error Numer Subject

error.c

#include <stdio.h>

int main() {
	float fsum1, fsum2;
	double dsum1, dsum2;
	int i,n;
	
	printf ("%5s%11s%11s%11s%11s%15s%15s\n","N","Float S1","Float S2","Double S1","Double S2","Error S1","Error S2");
	for (n=1000;n<=10000;n+=1000) {
		fsum1=fsum2=dsum1=dsum2=0;
		for (i=1;i<=n;i++) {
			fsum1+=1.0f/(i*i);
			fsum2+=1.0f/((n-i+1)*(n-i+1));
			dsum1+=1.0/(i*i);
			dsum2+=1.0/((n-i+1)*(n-i+1));
		}
		printf ("%5d%11f%11f%11lf%11lf%15e%15e\n",n,fsum1,fsum2,dsum1,dsum2,dsum1-fsum1,dsum2-fsum2);
	}	
	return 0;
}

/*
Result:
    N   Float S1   Float S2  Double S1  Double S2       Error S1       Error S2
 1000   1.643935   1.643934   1.643935   1.643935 -2.792428e-007  7.838505e-008
 2000   1.644432   1.644434   1.644434   1.644434  2.123956e-006 -2.181091e-008
 3000   1.644595   1.644601   1.644601   1.644601  6.119722e-006  4.004847e-008
 4000   1.644714   1.644684   1.644684   1.644684 -2.978054e-005  2.178642e-008
 5000   1.644725   1.644734   1.644734   1.644734  8.764124e-006 -5.736392e-008
 6000   1.644725   1.644767   1.644767   1.644767  4.209135e-005  1.046708e-008
 7000   1.644725   1.644791   1.644791   1.644791  6.589719e-005 -2.555155e-008
 8000   1.644725   1.644809   1.644809   1.644809  8.375194e-005  6.701575e-008
 9000   1.644725   1.644823   1.644823   1.644823  9.763919e-005  6.778195e-009
10000   1.644725   1.644834   1.644834   1.644834  1.087491e-004  3.025260e-008
*/