Created
October 5, 2015 21:28
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jaccard similarity using AVX2 SIMD
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#include <stdio.h> | |
#include <immintrin.h> | |
#include <stdint.h> | |
int intersectionSize(int* a, const int alen, int* b, const int blen) { | |
int ai = 0, bi = 0, size = 0; | |
while (ai < alen && bi < blen) { | |
int av = a[ai]; | |
int bv = b[bi]; | |
size += ((av == bv) ? 1 : 0); | |
ai += ((av <= bv) ? 1 : 0); | |
bi += ((av >= bv) ? 1 : 0); | |
} | |
return size; | |
} | |
#define SWAP(a, b) do { typeof(a) temp = a; a = b; b = temp; } while (0) | |
int intersectionSizeAVX(int* a, int alen, int* b, int blen) { | |
int *aa = a; | |
int *bb = b; | |
int size = 0; | |
int *a_end = a+alen-7; | |
int *b_end = b+blen-7; | |
while (a < a_end && b < b_end) { | |
if (*b > *a) { | |
SWAP(a, b); | |
SWAP(a_end, b_end); | |
SWAP(aa, bb); | |
SWAP(alen, blen); | |
} | |
__m256i q = _mm256_set1_epi32(*a); | |
__m256i bv = _mm256_loadu_si256((__m256i *)b); | |
__m256i cmp = _mm256_cmpgt_epi32(bv, q); // bv > q | |
uint32_t mask = ~_mm256_movemask_epi8(cmp); | |
uint32_t pos = 8 - _lzcnt_u32(mask) / 4; | |
b += pos; | |
size += ((*(b-1) == *a) ? 1 : 0); | |
a += (pos < 8 ? 1 : 0); | |
} | |
size += intersectionSize(a, aa+alen-a, b, bb+blen-b); | |
return size; | |
} | |
float jaccard(int* a, const int alen, int* b, const int blen) { | |
int is = intersectionSize(a, alen, b, blen); | |
int us = alen + blen - is; | |
return (us == 0) ? 0.0 : (is / (float) us); | |
} | |
float jaccardAVX(int* a, const int alen, int* b, const int blen) { | |
int is = intersectionSizeAVX(a, alen, b, blen); | |
int us = alen + blen - is; | |
return (us == 0) ? 0.0 : (is / (float) us); | |
} | |
int main(int argc, char *argv[]) { | |
int len = atoi(argv[1]); | |
int m = atoi(argv[2]); | |
int alen = len; | |
int blen = len; | |
int* a = malloc(alen * sizeof(int)); | |
int* b = malloc(blen * sizeof(int)); | |
for (int i = 0; i < alen; i++) a[i] = i; | |
for (int i = 0; i < blen; i++) b[i] = i*m; | |
long sum = 0; | |
for (int i = 0; i < 10000; i++) { | |
sum += intersectionSizeAVX(a, alen, b, blen); | |
} | |
printf("%ld\n", sum); | |
} |
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