Created
January 15, 2009 21:36
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| #include <stdio.h> | |
| #include <stdlib.h> | |
| #include <sys/time.h> | |
| #include <time.h> | |
| #include <string.h> | |
| #define SIZE (1024 * 1024 * 500) | |
| #define TIMES 10000000 | |
| #define START_TIMER() { \ | |
| struct timeval startt, endt; \ | |
| gettimeofday(&startt, NULL); \ | |
| #define END_TIMER(name) \ | |
| gettimeofday(&endt, NULL); \ | |
| printf("%20s: %8luus\n", name, 1000000 * (endt.tv_sec - startt.tv_sec) + (endt.tv_usec - startt.tv_usec)); \ | |
| } | |
| typedef struct { | |
| unsigned char type; | |
| union { | |
| int i; | |
| double d; | |
| void* p; | |
| } val; | |
| } struct1; | |
| // just to confirm that adding more doesn't increase the struct size | |
| typedef struct { | |
| unsigned char type; | |
| unsigned char flags; | |
| union { | |
| char c; | |
| int i; | |
| double d; | |
| void* p; | |
| } val; | |
| } struct2; | |
| // what if we use four-byte offsets, at the cost of an additional add | |
| // every time we dereference? i don't know if this is even doable. | |
| typedef struct { | |
| unsigned char type; | |
| unsigned char flags; | |
| union { | |
| char c; | |
| int i; | |
| int offset; | |
| } val; | |
| } struct3; | |
| int main(int argc, char* argv[]) { | |
| int i; | |
| void* mem; | |
| printf("sizeof(int) = %lu\n", sizeof(int)); | |
| printf("sizeof(int*) = %lu\n", sizeof(int*)); | |
| printf("sizeof(struct1) = %lu\n", sizeof(struct1)); | |
| printf("sizeof(struct2) = %lu\n", sizeof(struct2)); | |
| printf("sizeof(struct3) = %lu\n", sizeof(struct3)); | |
| START_TIMER(); | |
| mem = malloc(SIZE); | |
| END_TIMER("allocate"); | |
| // just curious how long this takes | |
| START_TIMER(); | |
| memset(mem, 9, SIZE); | |
| END_TIMER("memset"); | |
| START_TIMER(); | |
| for(i = 0; i < TIMES; i++) { | |
| unsigned int start = rand() % (SIZE / sizeof(struct1)); | |
| unsigned int end = rand() % (SIZE / sizeof(struct1)); | |
| } | |
| END_TIMER("empty loop"); | |
| printf("can fit %lu struct1's (size %lu)\n", SIZE / sizeof(struct1), sizeof(struct1)); | |
| START_TIMER(); | |
| for(i = 0; i < TIMES; i++) { | |
| unsigned int start = rand() % (SIZE / sizeof(struct1)); | |
| unsigned int end = rand() % (SIZE / sizeof(struct1)); | |
| *((struct1*)mem + start) = *((struct1*)mem + end); | |
| } | |
| END_TIMER("copying struct1s"); | |
| printf("can fit %lu struct3's (size %lu)\n", SIZE / sizeof(struct3), sizeof(struct3)); | |
| START_TIMER(); | |
| for(i = 0; i < TIMES; i++) { | |
| unsigned int start = rand() % (SIZE / sizeof(struct3)); | |
| unsigned int end = rand() % (SIZE / sizeof(struct3)); | |
| *((struct3*)mem + start) = *((struct3*)mem + end); | |
| } | |
| END_TIMER("copying struct3s"); | |
| printf("can fit %lu int's (size %lu)\n", SIZE / sizeof(int), sizeof(int)); | |
| START_TIMER(); | |
| for(i = 0; i < TIMES; i++) { | |
| unsigned int start = rand() % (SIZE / sizeof(int)); | |
| unsigned int end = rand() % (SIZE / sizeof(int)); | |
| *((int*)mem + start) = *((int*)mem + end); | |
| } | |
| END_TIMER("copying ints"); | |
| // sanity check | |
| START_TIMER(); | |
| sleep(2); | |
| END_TIMER("sleep(2)"); | |
| return 0; | |
| } |
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