My C Shit

p1.c

#define VERSION "P2V3_3 by Mark Provan. Updated last on 24/11/11\n"

#include <stdio.h>
#include <string.h>
#include <time.h>

static clock_t _startTick,_stopTick;
#define SNAP() (_startTick = clock())
#define SHOT() (_stopTick  = clock())
#define ELAPSED() (_stopTick - _startTick)

#define BLOCKSIZE 10000000
char str1[BLOCKSIZE];
char str2[BLOCKSIZE];

void * mymemcpyv1( void * destination, const void * source, size_t num ) {
  int i;
  for ( i = 0 ; i < num ; ++i ) {
    ((char *)destination)[i] = ((char *)source)[i];
  }
}

void * mymemcpyv2 ( void * destination, const void * source, size_t num ) {
	int i;
	for ( i = 0 ; i < num ; ++i ) {
		*((char *)destination + i) = *((char *)source + i);
	}
	return (destination);
}

void *mymemcpyv3 ( void *destination, const void *source, size_t num ) {
	char *dst = (char *) destination;
	const char *src = (char *) source;
	while (num--) {
		*dst++ = *src++;
	}
	return (destination);
}

int main ()
{	
	
	printf(VERSION);
	printf("\nOn this machine, CLOCKS_PER_SEC is %d\n", (int)CLOCKS_PER_SEC);
	printf("This means the timing accuracy is %f seconds\n\n", 1.0/CLOCKS_PER_SEC);
	printf("About to invoke a C memcopy of %d bytes\n", BLOCKSIZE);
	SNAP();
  	memcpy(str2,str1, BLOCKSIZE);
	SHOT();
	double runTimeLib = (double)ELAPSED()/CLOCKS_PER_SEC;
	printf("It took %f seconds to execute memcpy.\n", runTimeLib);
	printf("...at a speed of %f Mb/s.\n\n", ((BLOCKSIZE/runTimeLib)/1024)/1024);
	
	printf("Stage 2: About to invoke a mymemcpyv1 of %d bytes\n", BLOCKSIZE);
	SNAP();
	mymemcpyv1(str1, str2, BLOCKSIZE);
	SHOT();
	double myrunTime1 = (double)ELAPSED()/CLOCKS_PER_SEC;
	printf("It took %f seconds to execute mymemcpy.\n", myrunTime1);
	printf("...at a speed of %f Mb/s.\n\n", ((BLOCKSIZE/myrunTime1)/1024)/1024);
	
	printf("Stage 3: About to invoke a mymemcpyv2 of %d bytes\n", BLOCKSIZE);
	SNAP();
	mymemcpyv2(str1, str2, BLOCKSIZE);
	SHOT();
	double myrunTime2 = (double)ELAPSED()/CLOCKS_PER_SEC;
	printf("It took %f seconds to execute mymemcpy.\n", myrunTime2);
	printf("...at a speed of %f Mb/s.\n\n", ((BLOCKSIZE/myrunTime2)/1024)/1024);
	
	printf("Stage 4: About to invoke a mymemcpyv3 of %d bytes\n", BLOCKSIZE);
	SNAP();
	mymemcpyv3(str1, str2, BLOCKSIZE);
	SHOT();
	double myrunTime3 = (double)ELAPSED()/CLOCKS_PER_SEC;
	printf("It took %f seconds to execute mymemcpy.\n", myrunTime3);
	printf("...at a speed of %f Mb/s.\n\n\n", ((BLOCKSIZE/myrunTime3)/1024)/1024);
	
	/*Print out data for easier analysis */
	printf("             *****RESULTS******             \n\n");
	printf("----------------------------------------------\n");
	printf("| MEMCPY VERSION       | RUNTIME (SECS)      |\n");
	printf("----------------------------------------------\n");
	printf("| memcpy               |  %f           |\n", runTimeLib);
	printf("----------------------------------------------\n");
	printf("| mymemcpyv1           |  %f           |\n", myrunTime1);
	printf("----------------------------------------------\n");
	printf("| mymemcpyv2           |  %f           |\n", myrunTime2);
	printf("----------------------------------------------\n");
	printf("| mymemcpyv3           |  %f           |\n", myrunTime3);
	printf("----------------------------------------------\n\n");
	
	
	/*Determine the fastest function */
	double t[4] = {runTimeLib, myrunTime1, myrunTime2, myrunTime3};
	double fastest = 1000.00;
	int fastest_index = 0;
	int i=0;
	for (i=0; i<4; i++){
		if (t[i] < fastest ) {
			fastest = t[i];
			fastest_index = i;
		}
	}
	
	/* Assign the fastest function its respective name */
	char fastest_name[11];
	switch (fastest_index) {
		case 0 : strncpy(fastest_name, "memcpy", 6);
		fastest_name[6] = '\0'; 
			break;
		case 1 : strncpy(fastest_name, "mymemcpyv1", 10);
		fastest_name[10] = '\0';
			break;
		case 2 : strncpy(fastest_name, "mymemcpyv2", 10);
		fastest_name[10] = '\0';
			break;
		case 3 : strncpy(fastest_name, "mymemcpyv3", 10);
		fastest_name[10] = '\0';
			break;
			
	}
	/*Output fastest and terminate */
	printf("The quickest implementation of memcopy is %s, completing in %f seconds\n\n",fastest_name, t[fastest_index]);
	printf("Program Terminated\n\n");
	
  	return 0;
}