Created
July 13, 2017 02:34
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Super fast way to sort fixed integer arrays of size 7.
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#include <cstdlib> | |
#include <ctime> | |
#include <cstdio> | |
#include <sys/time.h> | |
#include <sys/resource.h> | |
#define NTESTS (5000000) | |
static double get_time() | |
{ | |
struct timeval t; | |
struct timezone tzp; | |
gettimeofday(&t, &tzp); | |
return t.tv_sec + t.tv_usec*1e-6; | |
} | |
static void sort7(int* a) { | |
#define max(x, y) (x ^ ((x ^ y) & -(x < y))) | |
#define min(x, y) (y ^ ((x ^ y) & -(x < y))) | |
#define SWAP(i, j) do { int temp = max(a[i], a[j]); a[i] = min(a[i], a[j]); a[j] = temp; } while(0) | |
// sorting network from the site below: | |
// http://pages.ripco.net/~jgamble/nw.html | |
SWAP(1, 2); SWAP(0, 2); SWAP(0, 1); SWAP(3, 4); | |
SWAP(5, 6); SWAP(3, 5); SWAP(4, 6); SWAP(4, 5); | |
SWAP(0, 4); SWAP(0, 3); SWAP(1, 5); SWAP(2, 6); | |
SWAP(2, 5); SWAP(1, 3); SWAP(2, 4); SWAP(2, 3); | |
#undef SWAP | |
#undef min | |
#undef max | |
} | |
int main() { | |
srand(time(NULL)); | |
// init test cases | |
int* arr = new int[7 * NTESTS]; | |
for (int i = 0; i < 7 * NTESTS; i++) { | |
arr[i] = rand(); | |
} | |
// begin testing | |
double startTime = get_time(); | |
for (int i = 0; i < NTESTS; i++) { | |
sort7(&arr[7 * i]); | |
} | |
double elapsed = get_time() - startTime; | |
// verify | |
for (int i = 0; i < NTESTS; i++) { | |
for (int j = 0; j < 6; j++) { | |
if (arr[7 * i + j] > arr[7 * i + j + 1]) { | |
printf("FAILED!!!\n"); | |
return 1; | |
} | |
} | |
} | |
printf("Completed %d sorts in %lfs\n", NTESTS, elapsed); | |
} |
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