#include <cstdio>
#include <ctime>

const double TEMPOEXECUCAO = 300;

union casting {
	int i;
	float f;
};

float InvSqrt (float x) {
   union casting cast;
   float xhalf = 0.5f*x;
   cast.f = x;					//   int i = *(int*)&x;
   cast.i = 0x5f3759df - ((cast.i)>>1);		//   x = *(float*)&i;
   return cast.f*(1.5f - xhalf*cast.f*cast.f); //   x = x*(1.5f - xhalf*x*x);
}


int main(void){
	time_t tStart, tActual;
	long int termosPorSegundo = 0l;				// contador de termos gerados
	float i=1.f;					// i-esimo termo
	double t1,t2;

	time(&tStart); time(&tActual);

	t1 = difftime(tActual, tStart);
	t2 = t1;


	printf("Tempo versus Termos Criados.\n");

	while(t1 < TEMPOEXECUCAO){
		InvSqrt(i++);		
		
	
		if((int)t2 == (int)(t1+1)){
			printf("%0.0f\t%ld\n",t1,termosPorSegundo);
			termosPorSegundo = 0;
			t1 = difftime(tActual, tStart);
			t2 = t1;			
		}else{
			termosPorSegundo++;
			t2 = difftime(tActual, tStart);	
		}

		time(&tActual);				
	}
}