exercise02_mem_hierarchy.c

/* Source: http://www.hpl.hp.com/research/cacti/aca_ch2_cs2.c */

//#include "stdafx.h"
#include <stdio.h>
#include <time.h>
#include <sys/time.h>    

#define ARRAY_MIN (1024) /* 1/4 smallest cache */
#define ARRAY_MAX (4096*4096) /* 1/4 largest cache */

int x[ARRAY_MAX]; /* array going to stride through */

long get_seconds() { /* routine to read time in seconds */
//double get_seconds() { /* routine to read time in seconds */
//__time64_t ltime;
//_time64( &ltime );
//return (double) ltime;

return time ( NULL ); // time in seconds

/*long usec;
struct timeval tp;
gettimeofday ( &tp, NULL );
usec = tp.tv_sec * 1E6 + tp.tv_usec;
return usec;*/
}

int label(int i) {/* generate text labels */
if (i<1e3) printf("%1dB,",i);
else if (i<1e6) printf("%1dK,",i/1024);
else if (i<1e9) printf("%1dM,",i/1048576);
else printf("%1dG,",i/1073741824);
return 0;
}

int main(int argc, char* argv[]) 
{
int register nextstep, i, index, stride;
int csize;
double steps, tsteps;
double loadtime, lastsec, sec0, sec1, sec; /* timing variables */

/* Initialize output */
printf(" ,");
for (stride=1; stride <= ARRAY_MAX/2; stride=stride*2)
	label(stride*sizeof(int));
printf("\n");

/* Main loop for each configuration */
for (csize=ARRAY_MIN; csize <= ARRAY_MAX; csize=csize*2) 
	{
	label(csize*sizeof(int)); /* print cache size this loop */
	for (stride=1; stride <= csize/2; stride=stride*2) {
	
		/* Lay out path of memory references in array */
		for (index=0; index < csize; index=index+stride)
			x[index] = index + stride; /* pointer to next */		
		x[index-stride] = 0; /* loop back to beginning */
		
		/* Wait for timer to roll over */
		lastsec = get_seconds();
		do sec0 = get_seconds(); while (sec0 == lastsec);
		
		/* Walk through path in array for twenty seconds */
		/* This gives 5% accuracy with second resolution */
		steps = 0.0; /* number of steps taken */
		nextstep = 0; /* start at beginning of path */
		sec0 = get_seconds(); /* start timer */
		do { /* repeat until collect 20 seconds */
			for (i=stride;i!=0;i=i-1) { /* keep samples same */
				nextstep = 0;
				do nextstep = x[nextstep]; /* dependency */
				while (nextstep != 0);
			}
			steps = steps + 1.0; /* count loop iterations */
			sec1 = get_seconds(); /* end timer */
		//} while ((sec1 - sec0) < 5000000); // collect .5 seconds
		} while ((sec1 - sec0) < 20); /* collect 20 seconds */
		sec = sec1 - sec0;
		
		/* Repeat empty loop to loop subtract overhead */
		tsteps = 0.0; /* used to match no. while iterations */
		sec0 = get_seconds(); /* start timer */
		do { /* repeat until same no. iterations as above */
			for (i=stride;i!=0;i=i-1) { /* keep samples same */
				index = 0;
				do index = index + stride;
				while (index < csize);
			}
			tsteps = tsteps + 1.0;
			sec1 = get_seconds(); /* - overhead */
		} while (tsteps<steps); /* until = no. iterations */
		sec = sec - (sec1 - sec0);
		//sec /= 1E6;
		loadtime = (sec*1e9)/(steps*csize);
		/* write out results in .csv format for Excel */
		printf("%4.1f,", (loadtime<0.1) ? 0.1 : loadtime);
	}; /* end of inner for loop */

	printf("\n");
	}; /* end of outer for loop */
return 0;
}