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Better NEON Hamming distance

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This commit is contained in:
Andrey Kamaev
2011-10-26 13:04:53 +00:00
parent 509730c1cd
commit d7ff92439d
5 changed files with 42 additions and 38 deletions
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49
modules/flann/include/opencv2/flann/dist.h
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@@ -421,43 +421,42 @@ struct Hamming
{
ResultType result = 0;
#if __GNUC__
#if ANDROID && HAVE_NEON
static uint64_t features = android_getCpuFeatures();
if ((features& ANDROID_CPU_ARM_FEATURE_NEON)) {
#if CV_NEON
if (CPU_HAS_NEON_FEATURE) {
uint32x4_t bits = vmovq_n_u32(0);
for (size_t i = 0; i < size; i += 16) {
uint8x16_t A_vec = vld1q_u8 (a + i);
uint8x16_t B_vec = vld1q_u8 (b + i);
//uint8x16_t veorq_u8 (uint8x16_t, uint8x16_t)
uint8x16_t AxorB = veorq_u8 (A_vec, B_vec);
uint8x16_t bitsSet += vcntq_u8 (AxorB);
//uint16x8_t vpadalq_u8 (uint16x8_t, uint8x16_t)
uint8x16_t bitsSet = vcntq_u8 (AxorB);
uint16x8_t bitSet8 = vpaddlq_u8 (bitsSet);
uint32x4_t bitSet4 = vpaddlq_u16 (bitSet8);
uint64x2_t bitSet2 = vpaddlq_u32 (bitSet4);
result += vgetq_lane_u64 (bitSet2,0);
result += vgetq_lane_u64 (bitSet2,1);
bits = vaddq_u32(bits, bitSet4);
}
uint64x2_t bitSet2 = vpaddlq_u32 (bits);
result = vgetq_lane_s32 (vreinterpretq_s32_u64(bitSet2),0);
result += vgetq_lane_s32 (vreinterpretq_s32_u64(bitSet2),2);
}
else
#endif
//for portability just use unsigned long -- and use the __builtin_popcountll (see docs for __builtin_popcountll)
typedef unsigned long long pop_t;
const size_t modulo = size % sizeof(pop_t);
const pop_t* a2 = reinterpret_cast<const pop_t*> (a);
const pop_t* b2 = reinterpret_cast<const pop_t*> (b);
const pop_t* a2_end = a2 + (size / sizeof(pop_t));
{
//for portability just use unsigned long -- and use the __builtin_popcountll (see docs for __builtin_popcountll)
typedef unsigned long long pop_t;
const size_t modulo = size % sizeof(pop_t);
const pop_t* a2 = reinterpret_cast<const pop_t*> (a);
const pop_t* b2 = reinterpret_cast<const pop_t*> (b);
const pop_t* a2_end = a2 + (size / sizeof(pop_t));
for (; a2 != a2_end; ++a2, ++b2) result += __builtin_popcountll((*a2) ^ (*b2));
for (; a2 != a2_end; ++a2, ++b2) result += __builtin_popcountll((*a2) ^ (*b2));
if (modulo) {
//in the case where size is not dividable by sizeof(size_t)
//need to mask off the bits at the end
pop_t a_final = 0, b_final = 0;
memcpy(&a_final, a2, modulo);
memcpy(&b_final, b2, modulo);
result += __builtin_popcountll(a_final ^ b_final);
if (modulo) {
//in the case where size is not dividable by sizeof(size_t)
//need to mask off the bits at the end
pop_t a_final = 0, b_final = 0;
memcpy(&a_final, a2, modulo);
memcpy(&b_final, b2, modulo);
result += __builtin_popcountll(a_final ^ b_final);
}
}
#else
HammingLUT lut;