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Replace SSE3 intrinsics in Index2Layer with portable scalar code (#5076) #5076

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algoriddle wants to merge 1 commit into from
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Replace SSE3 intrinsics in Index2Layer with portable scalar code (#5076) #5076

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65 changes: 23 additions & 42 deletions faiss/Index2Layer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -13,10 +13,6 @@
#include <cstdint>
#include <cstdio>

#ifdef __SSE3__
#include <immintrin.h>
#endif

#include <algorithm>

#include <faiss/IndexIVFPQ.h>
Expand Down Expand Up @@ -177,34 +173,26 @@ struct DistanceXPQ4 : Distance2Level {
}

float operator()(idx_t i) override {
#ifdef __SSE3__
const uint8_t* code = storage.codes.data() + i * storage.code_size;
idx_t key = 0;
memcpy(&key, code, storage.code_size_1);
code += storage.code_size_1;

// walking pointers
const float* qa = q;
const __m128* l1_t = (const __m128*)(pq_l1_tab + d * key);
const __m128* pq_l2_t = (const __m128*)pq_l2_tab;
__m128 accu = _mm_setzero_ps();
const float* l1 = pq_l1_tab + d * key;
const float* l2 = pq_l2_tab;
float accu = 0;

for (int m = 0; m < M; m++) {
__m128 qi = _mm_loadu_ps(qa);
__m128 recons = _mm_add_ps(l1_t[m], pq_l2_t[*code++]);
__m128 diff = _mm_sub_ps(qi, recons);
accu = _mm_add_ps(accu, _mm_mul_ps(diff, diff));
pq_l2_t += 256;
for (int j = 0; j < 4; j++) {
float diff = qa[j] - (l1[m * 4 + j] + l2[*code * 4 + j]);
accu += diff * diff;
}
code++;
l2 += 256 * 4;
qa += 4;
}

accu = _mm_hadd_ps(accu, accu);
accu = _mm_hadd_ps(accu, accu);
return _mm_cvtss_f32(accu);
#else
(void)i;
FAISS_THROW_MSG("not implemented for non-x64 platforms");
#endif
return accu;
}
};

Expand All @@ -229,42 +217,36 @@ struct Distance2xXPQ4 : Distance2Level {
int64_t key01 = 0;
memcpy(&key01, code, storage.code_size_1);
code += storage.code_size_1;
#ifdef __SSE3__

// walking pointers
const float* qa = q;
const __m128* pq_l1_t = (const __m128*)pq_l1_tab;
const __m128* pq_l2_t = (const __m128*)pq_l2_tab;
__m128 accu = _mm_setzero_ps();
const float* l1 = pq_l1_tab;
const float* l2 = pq_l2_tab;
float accu = 0;

for (int mi_m = 0; mi_m < 2; mi_m++) {
int64_t l1_idx = key01 & (((int64_t)1 << mi_nbits) - 1);
const __m128* pq_l1 = pq_l1_t + M_2 * l1_idx;
const float* l1_sub = l1 + M_2 * l1_idx * 4;

for (int m = 0; m < M_2; m++) {
__m128 qi = _mm_loadu_ps(qa);
__m128 recons = _mm_add_ps(pq_l1[m], pq_l2_t[*code++]);
__m128 diff = _mm_sub_ps(qi, recons);
accu = _mm_add_ps(accu, _mm_mul_ps(diff, diff));
pq_l2_t += 256;
for (int j = 0; j < 4; j++) {
float diff =
qa[j] - (l1_sub[m * 4 + j] + l2[*code * 4 + j]);
accu += diff * diff;
}
code++;
l2 += 256 * 4;
qa += 4;
}
pq_l1_t += M_2 << mi_nbits;
l1 += (M_2 << mi_nbits) * 4;
key01 >>= mi_nbits;
}
accu = _mm_hadd_ps(accu, accu);
accu = _mm_hadd_ps(accu, accu);
return _mm_cvtss_f32(accu);
#else
FAISS_THROW_MSG("not implemented for non-x64 platforms");
#endif
return accu;
}
};

} // namespace

DistanceComputer* Index2Layer::get_distance_computer() const {
#ifdef __SSE3__
const MultiIndexQuantizer* mi =
dynamic_cast<MultiIndexQuantizer*>(q1.quantizer);

Expand All @@ -277,7 +259,6 @@ DistanceComputer* Index2Layer::get_distance_computer() const {
if (fl && pq.dsub == 4) {
return new DistanceXPQ4(*this);
}
#endif

return Index::get_distance_computer();
}
Expand Down
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