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stockfish/src/nnue/layers/affine_transform.h

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/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2021 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
// Definition of layer AffineTransform of NNUE evaluation function
#ifndef NNUE_LAYERS_AFFINE_TRANSFORM_H_INCLUDED
#define NNUE_LAYERS_AFFINE_TRANSFORM_H_INCLUDED
#include <iostream>
#include <algorithm>
#include <type_traits>
#include "../nnue_common.h"
#include "../../simd.h"
/*
This file contains the definition for a fully connected layer (aka affine transform).
Two approaches are employed, depending on the sizes of the transform.
Approach 1:
- used when the PaddedInputDimensions >= 128
- uses AVX512 if possible
- processes inputs in batches of 2*InputSimdWidth
- so in batches of 128 for AVX512
- the weight blocks of size InputSimdWidth are transposed such that
access is sequential
- N columns of the weight matrix are processed a time, where N
depends on the architecture (the amount of registers)
- accumulate + hadd is used
Approach 2:
- used when the PaddedInputDimensions < 128
- does not use AVX512
- expected use-case is for when PaddedInputDimensions == 32 and InputDimensions <= 32.
- that's why AVX512 is hard to implement
- expected use-case is small layers
- not optimized as well as the approach 1
- inputs are processed in chunks of 4, weights are respectively transposed
- accumulation happens directly to int32s
*/
namespace Stockfish::Eval::NNUE::Layers {
// Fallback implementation for older/other architectures.
// Identical for both approaches. Requires the input to be padded to at least 16 values.
#if !defined(USE_SSSE3)
template <IndexType InputDimensions, IndexType PaddedInputDimensions, IndexType OutputDimensions>
static void affine_transform_non_ssse3(std::int32_t* output, const std::int8_t* weights, const std::int32_t* biases, const std::uint8_t* input)
{
# if defined(USE_SSE2)
// At least a multiple of 16, with SSE2.
static_assert(PaddedInputDimensions % 16 == 0);
constexpr IndexType NumChunks = PaddedInputDimensions / 16;
const __m128i Zeros = _mm_setzero_si128();
const auto inputVector = reinterpret_cast<const __m128i*>(input);
# elif defined(USE_MMX)
static_assert(InputDimensions % 8 == 0);
constexpr IndexType NumChunks = InputDimensions / 8;
const __m64 Zeros = _mm_setzero_si64();
const auto inputVector = reinterpret_cast<const __m64*>(input);
# elif defined(USE_NEON)
static_assert(PaddedInputDimensions % 16 == 0);
constexpr IndexType NumChunks = PaddedInputDimensions / 16;
const auto inputVector = reinterpret_cast<const int8x8_t*>(input);
# endif
for (IndexType i = 0; i < OutputDimensions; ++i) {
const IndexType offset = i * PaddedInputDimensions;
# if defined(USE_SSE2)
__m128i sumLo = _mm_cvtsi32_si128(biases[i]);
__m128i sumHi = Zeros;
const auto row = reinterpret_cast<const __m128i*>(&weights[offset]);
for (IndexType j = 0; j < NumChunks; ++j) {
__m128i row_j = _mm_load_si128(&row[j]);
__m128i input_j = _mm_load_si128(&inputVector[j]);
__m128i extendedRowLo = _mm_srai_epi16(_mm_unpacklo_epi8(row_j, row_j), 8);
__m128i extendedRowHi = _mm_srai_epi16(_mm_unpackhi_epi8(row_j, row_j), 8);
__m128i extendedInputLo = _mm_unpacklo_epi8(input_j, Zeros);
__m128i extendedInputHi = _mm_unpackhi_epi8(input_j, Zeros);
__m128i productLo = _mm_madd_epi16(extendedRowLo, extendedInputLo);
__m128i productHi = _mm_madd_epi16(extendedRowHi, extendedInputHi);
sumLo = _mm_add_epi32(sumLo, productLo);
sumHi = _mm_add_epi32(sumHi, productHi);
}
__m128i sum = _mm_add_epi32(sumLo, sumHi);
__m128i sumHigh_64 = _mm_shuffle_epi32(sum, _MM_SHUFFLE(1, 0, 3, 2));
sum = _mm_add_epi32(sum, sumHigh_64);
__m128i sum_second_32 = _mm_shufflelo_epi16(sum, _MM_SHUFFLE(1, 0, 3, 2));
sum = _mm_add_epi32(sum, sum_second_32);
output[i] = _mm_cvtsi128_si32(sum);
# elif defined(USE_MMX)
__m64 sumLo = _mm_cvtsi32_si64(biases[i]);
__m64 sumHi = Zeros;
const auto row = reinterpret_cast<const __m64*>(&weights[offset]);
for (IndexType j = 0; j < NumChunks; ++j) {
__m64 row_j = row[j];
__m64 input_j = inputVector[j];
__m64 extendedRowLo = _mm_srai_pi16(_mm_unpacklo_pi8(row_j, row_j), 8);
__m64 extendedRowHi = _mm_srai_pi16(_mm_unpackhi_pi8(row_j, row_j), 8);
__m64 extendedInputLo = _mm_unpacklo_pi8(input_j, Zeros);
__m64 extendedInputHi = _mm_unpackhi_pi8(input_j, Zeros);
__m64 productLo = _mm_madd_pi16(extendedRowLo, extendedInputLo);
__m64 productHi = _mm_madd_pi16(extendedRowHi, extendedInputHi);
sumLo = _mm_add_pi32(sumLo, productLo);
sumHi = _mm_add_pi32(sumHi, productHi);
}
__m64 sum = _mm_add_pi32(sumLo, sumHi);
sum = _mm_add_pi32(sum, _mm_unpackhi_pi32(sum, sum));
output[i] = _mm_cvtsi64_si32(sum);
# elif defined(USE_NEON)
int32x4_t sum = {biases[i]};
const auto row = reinterpret_cast<const int8x8_t*>(&weights[offset]);
for (IndexType j = 0; j < NumChunks; ++j) {
int16x8_t product = vmull_s8(inputVector[j * 2], row[j * 2]);
product = vmlal_s8(product, inputVector[j * 2 + 1], row[j * 2 + 1]);
sum = vpadalq_s16(sum, product);
}
output[i] = sum[0] + sum[1] + sum[2] + sum[3];
# else
std::int32_t sum = biases[i];
for (IndexType j = 0; j < InputDimensions; ++j) {
sum += weights[offset + j] * input[j];
}
output[i] = sum;
# endif
}
# if defined(USE_MMX)
_mm_empty();
# endif
}
#endif
template <typename PreviousLayer, IndexType OutDims, typename Enabled = void>
class AffineTransform;
// A specialization for large inputs.
template <typename PreviousLayer, IndexType OutDims>
class AffineTransform<PreviousLayer, OutDims, std::enable_if_t<(PreviousLayer::OutputDimensions >= 2*64-1)>> {
public:
// Input/output type
using InputType = typename PreviousLayer::OutputType;
using OutputType = std::int32_t;
static_assert(std::is_same<InputType, std::uint8_t>::value, "");
// Number of input/output dimensions
static constexpr IndexType InputDimensions = PreviousLayer::OutputDimensions;
static constexpr IndexType OutputDimensions = OutDims;
static constexpr IndexType PaddedInputDimensions =
ceil_to_multiple<IndexType>(InputDimensions, MaxSimdWidth);
static_assert(PaddedInputDimensions >= 128, "Something went wrong. This specialization should not have been chosen.");
#if defined (USE_AVX512)
static constexpr const IndexType InputSimdWidth = 64;
static constexpr const IndexType MaxNumOutputRegs = 16;
#elif defined (USE_AVX2)
static constexpr const IndexType InputSimdWidth = 32;
static constexpr const IndexType MaxNumOutputRegs = 8;
#elif defined (USE_SSSE3)
static constexpr const IndexType InputSimdWidth = 16;
static constexpr const IndexType MaxNumOutputRegs = 8;
#else
// The fallback implementation will not have permuted weights.
// We define these to avoid a lot of ifdefs later.
static constexpr const IndexType InputSimdWidth = 1;
static constexpr const IndexType MaxNumOutputRegs = 1;
#endif
// A big block is a region in the weight matrix of the size [PaddedInputDimensions, NumOutputRegs].
// A small block is a region of size [InputSimdWidth, 1]
static constexpr const IndexType NumOutputRegs = std::min(MaxNumOutputRegs, OutputDimensions);
static constexpr const IndexType SmallBlockSize = InputSimdWidth;
static constexpr const IndexType BigBlockSize = NumOutputRegs * PaddedInputDimensions;
static constexpr const IndexType NumSmallBlocksInBigBlock = BigBlockSize / SmallBlockSize;
static constexpr const IndexType NumSmallBlocksPerOutput = PaddedInputDimensions / SmallBlockSize;
static constexpr const IndexType NumBigBlocks = OutputDimensions / NumOutputRegs;
static_assert(OutputDimensions % NumOutputRegs == 0);
// Size of forward propagation buffer used in this layer
static constexpr std::size_t SelfBufferSize =
ceil_to_multiple(OutputDimensions * sizeof(OutputType), CacheLineSize);
// Size of the forward propagation buffer used from the input layer to this layer
static constexpr std::size_t BufferSize =
PreviousLayer::BufferSize + SelfBufferSize;
// Hash value embedded in the evaluation file
static constexpr std::uint32_t get_hash_value() {
std::uint32_t hashValue = 0xCC03DAE4u;
hashValue += OutputDimensions;
hashValue ^= PreviousLayer::get_hash_value() >> 1;
hashValue ^= PreviousLayer::get_hash_value() << 31;
return hashValue;
}
/*
Transposes the small blocks within a block.
Effectively means that weights can be traversed sequentially during inference.
*/
static IndexType get_weight_index(IndexType i)
{
const IndexType smallBlock = (i / SmallBlockSize) % NumSmallBlocksInBigBlock;
const IndexType smallBlockCol = smallBlock / NumSmallBlocksPerOutput;
const IndexType smallBlockRow = smallBlock % NumSmallBlocksPerOutput;
const IndexType bigBlock = i / BigBlockSize;
const IndexType rest = i % SmallBlockSize;
const IndexType idx =
bigBlock * BigBlockSize
+ smallBlockRow * SmallBlockSize * NumOutputRegs
+ smallBlockCol * SmallBlockSize
+ rest;
return idx;
}
// Read network parameters
bool read_parameters(std::istream& stream) {
if (!previousLayer.read_parameters(stream)) return false;
for (std::size_t i = 0; i < OutputDimensions; ++i)
biases[i] = read_little_endian<BiasType>(stream);
for (std::size_t i = 0; i < OutputDimensions * PaddedInputDimensions; ++i)
weights[get_weight_index(i)] = read_little_endian<WeightType>(stream);
return !stream.fail();
}
// Write network parameters
bool write_parameters(std::ostream& stream) const {
if (!previousLayer.write_parameters(stream)) return false;
for (std::size_t i = 0; i < OutputDimensions; ++i)
write_little_endian<BiasType>(stream, biases[i]);
for (std::size_t i = 0; i < OutputDimensions * PaddedInputDimensions; ++i)
write_little_endian<WeightType>(stream, weights[get_weight_index(i)]);
return !stream.fail();
}
// Forward propagation
const OutputType* propagate(
const TransformedFeatureType* transformedFeatures, char* buffer) const {
const auto input = previousLayer.propagate(
transformedFeatures, buffer + SelfBufferSize);
OutputType* output = reinterpret_cast<OutputType*>(buffer);
#if defined (USE_AVX512)
using vec_t = __m512i;
#define vec_setzero _mm512_setzero_si512
#define vec_set_32 _mm512_set1_epi32
#define vec_add_dpbusd_32 Simd::m512_add_dpbusd_epi32
#define vec_add_dpbusd_32x2 Simd::m512_add_dpbusd_epi32x2
#define vec_hadd Simd::m512_hadd
#define vec_haddx4 Simd::m512_haddx4
#elif defined (USE_AVX2)
using vec_t = __m256i;
#define vec_setzero _mm256_setzero_si256
#define vec_set_32 _mm256_set1_epi32
#define vec_add_dpbusd_32 Simd::m256_add_dpbusd_epi32
#define vec_add_dpbusd_32x2 Simd::m256_add_dpbusd_epi32x2
#define vec_hadd Simd::m256_hadd
#define vec_haddx4 Simd::m256_haddx4
#elif defined (USE_SSSE3)
using vec_t = __m128i;
#define vec_setzero _mm_setzero_si128
#define vec_set_32 _mm_set1_epi32
#define vec_add_dpbusd_32 Simd::m128_add_dpbusd_epi32
#define vec_add_dpbusd_32x2 Simd::m128_add_dpbusd_epi32x2
#define vec_hadd Simd::m128_hadd
#define vec_haddx4 Simd::m128_haddx4
#endif
#if defined (USE_SSSE3)
const vec_t* invec = reinterpret_cast<const vec_t*>(input);
// Perform accumulation to registers for each big block
for (IndexType bigBlock = 0; bigBlock < NumBigBlocks; ++bigBlock)
{
vec_t acc[NumOutputRegs] = { vec_setzero() };
// Each big block has NumOutputRegs small blocks in each "row", one per register.
// We process two small blocks at a time to save on one addition without VNNI.
for (IndexType smallBlock = 0; smallBlock < NumSmallBlocksPerOutput; smallBlock += 2)
{
const vec_t* weightvec =
reinterpret_cast<const vec_t*>(
weights
+ bigBlock * BigBlockSize
+ smallBlock * SmallBlockSize * NumOutputRegs);
const vec_t in0 = invec[smallBlock + 0];
const vec_t in1 = invec[smallBlock + 1];
for (IndexType k = 0; k < NumOutputRegs; ++k)
vec_add_dpbusd_32x2(acc[k], in0, weightvec[k], in1, weightvec[k + NumOutputRegs]);
}
// Horizontally add all accumulators.
if constexpr (NumOutputRegs % 4 == 0)
{
__m128i* outputvec = reinterpret_cast<__m128i*>(output);
const __m128i* biasvec = reinterpret_cast<const __m128i*>(biases);
for (IndexType k = 0; k < NumOutputRegs; k += 4)
{
const IndexType idx = (bigBlock * NumOutputRegs + k) / 4;
outputvec[idx] = vec_haddx4(acc[k+0], acc[k+1], acc[k+2], acc[k+3], biasvec[idx]);
}
}
else
{
for (IndexType k = 0; k < NumOutputRegs; ++k)
{
const IndexType idx = (bigBlock * NumOutputRegs + k);
output[idx] = vec_hadd(acc[k], biases[idx]);
}
}
}
# undef vec_setzero
# undef vec_set_32
# undef vec_add_dpbusd_32
# undef vec_add_dpbusd_32x2
# undef vec_hadd
# undef vec_haddx4
#else
// Use old implementation for the other architectures.
affine_transform_non_ssse3<
InputDimensions,
PaddedInputDimensions,
OutputDimensions>(output, weights, biases, input);
#endif
return output;
}
private:
using BiasType = OutputType;
using WeightType = std::int8_t;
PreviousLayer previousLayer;
alignas(CacheLineSize) BiasType biases[OutputDimensions];
alignas(CacheLineSize) WeightType weights[OutputDimensions * PaddedInputDimensions];
};
template <typename PreviousLayer, IndexType OutDims>
class AffineTransform<PreviousLayer, OutDims, std::enable_if_t<(PreviousLayer::OutputDimensions < 2*64-1)>> {
public:
// Input/output type
using InputType = typename PreviousLayer::OutputType;
using OutputType = std::int32_t;
static_assert(std::is_same<InputType, std::uint8_t>::value, "");
// Number of input/output dimensions
static constexpr IndexType InputDimensions =
PreviousLayer::OutputDimensions;
static constexpr IndexType OutputDimensions = OutDims;
static constexpr IndexType PaddedInputDimensions =
ceil_to_multiple<IndexType>(InputDimensions, MaxSimdWidth);
static_assert(PaddedInputDimensions < 128, "Something went wrong. This specialization should not have been chosen.");
#if defined (USE_SSSE3)
static constexpr const IndexType OutputSimdWidth = SimdWidth / 4;
static constexpr const IndexType InputSimdWidth = SimdWidth;
#endif
// Size of forward propagation buffer used in this layer
static constexpr std::size_t SelfBufferSize =
ceil_to_multiple(OutputDimensions * sizeof(OutputType), CacheLineSize);
// Size of the forward propagation buffer used from the input layer to this layer
static constexpr std::size_t BufferSize =
PreviousLayer::BufferSize + SelfBufferSize;
// Hash value embedded in the evaluation file
static constexpr std::uint32_t get_hash_value() {
std::uint32_t hashValue = 0xCC03DAE4u;
hashValue += OutputDimensions;
hashValue ^= PreviousLayer::get_hash_value() >> 1;
hashValue ^= PreviousLayer::get_hash_value() << 31;
return hashValue;
}
static IndexType get_weight_index_scrambled(IndexType i)
{
return
(i / 4) % (PaddedInputDimensions / 4) * OutputDimensions * 4 +
i / PaddedInputDimensions * 4 +
i % 4;
}
static IndexType get_weight_index(IndexType i)
{
#if defined (USE_SSSE3)
return get_weight_index_scrambled(i);
#else
return i;
#endif
}
// Read network parameters
bool read_parameters(std::istream& stream) {
if (!previousLayer.read_parameters(stream)) return false;
for (std::size_t i = 0; i < OutputDimensions; ++i)
biases[i] = read_little_endian<BiasType>(stream);
for (std::size_t i = 0; i < OutputDimensions * PaddedInputDimensions; ++i)
weights[get_weight_index(i)] = read_little_endian<WeightType>(stream);
return !stream.fail();
}
// Write network parameters
bool write_parameters(std::ostream& stream) const {
if (!previousLayer.write_parameters(stream)) return false;
for (std::size_t i = 0; i < OutputDimensions; ++i)
write_little_endian<BiasType>(stream, biases[i]);
for (std::size_t i = 0; i < OutputDimensions * PaddedInputDimensions; ++i)
write_little_endian<WeightType>(stream, weights[get_weight_index(i)]);
return !stream.fail();
}
// Forward propagation
const OutputType* propagate(
const TransformedFeatureType* transformedFeatures, char* buffer) const {
const auto input = previousLayer.propagate(
transformedFeatures, buffer + SelfBufferSize);
const auto output = reinterpret_cast<OutputType*>(buffer);
#if defined (USE_AVX2)
using vec_t = __m256i;
#define vec_setzero _mm256_setzero_si256
#define vec_set_32 _mm256_set1_epi32
#define vec_add_dpbusd_32 Simd::m256_add_dpbusd_epi32
#define vec_add_dpbusd_32x2 Simd::m256_add_dpbusd_epi32x2
#define vec_add_dpbusd_32x4 Simd::m256_add_dpbusd_epi32x4
#define vec_hadd Simd::m256_hadd
#define vec_haddx4 Simd::m256_haddx4
#elif defined (USE_SSSE3)
using vec_t = __m128i;
#define vec_setzero _mm_setzero_si128
#define vec_set_32 _mm_set1_epi32
#define vec_add_dpbusd_32 Simd::m128_add_dpbusd_epi32
#define vec_add_dpbusd_32x2 Simd::m128_add_dpbusd_epi32x2
#define vec_add_dpbusd_32x4 Simd::m128_add_dpbusd_epi32x4
#define vec_hadd Simd::m128_hadd
#define vec_haddx4 Simd::m128_haddx4
#endif
#if defined (USE_SSSE3)
const auto inputVector = reinterpret_cast<const vec_t*>(input);
static_assert(InputDimensions % 8 == 0);
static_assert(OutputDimensions % OutputSimdWidth == 0 || OutputDimensions == 1);
if constexpr (OutputDimensions % OutputSimdWidth == 0)
{
constexpr IndexType NumChunks = InputDimensions / 4;
constexpr IndexType NumRegs = OutputDimensions / OutputSimdWidth;
const auto input32 = reinterpret_cast<const std::int32_t*>(input);
const vec_t* biasvec = reinterpret_cast<const vec_t*>(biases);
vec_t acc[NumRegs];
for (IndexType k = 0; k < NumRegs; ++k)
acc[k] = biasvec[k];
for (IndexType i = 0; i < NumChunks; i += 2)
{
const vec_t in0 = vec_set_32(input32[i + 0]);
const vec_t in1 = vec_set_32(input32[i + 1]);
const auto col0 = reinterpret_cast<const vec_t*>(&weights[(i + 0) * OutputDimensions * 4]);
const auto col1 = reinterpret_cast<const vec_t*>(&weights[(i + 1) * OutputDimensions * 4]);
for (IndexType k = 0; k < NumRegs; ++k)
vec_add_dpbusd_32x2(acc[k], in0, col0[k], in1, col1[k]);
}
vec_t* outptr = reinterpret_cast<vec_t*>(output);
for (IndexType k = 0; k < NumRegs; ++k)
outptr[k] = acc[k];
}
else if constexpr (OutputDimensions == 1)
{
constexpr IndexType NumChunks = PaddedInputDimensions / SimdWidth;
vec_t sum0 = vec_setzero();
const auto row0 = reinterpret_cast<const vec_t*>(&weights[0]);
for (int j = 0; j < (int)NumChunks; ++j)
{
const vec_t in = inputVector[j];
vec_add_dpbusd_32(sum0, in, row0[j]);
}
output[0] = vec_hadd(sum0, biases[0]);
}
# undef vec_setzero
# undef vec_set_32
# undef vec_add_dpbusd_32
# undef vec_add_dpbusd_32x2
# undef vec_add_dpbusd_32x4
# undef vec_hadd
# undef vec_haddx4
#else
// Use old implementation for the other architectures.
affine_transform_non_ssse3<
InputDimensions,
PaddedInputDimensions,
OutputDimensions>(output, weights, biases, input);
#endif
return output;
}
private:
using BiasType = OutputType;
using WeightType = std::int8_t;
PreviousLayer previousLayer;
alignas(CacheLineSize) BiasType biases[OutputDimensions];
alignas(CacheLineSize) WeightType weights[OutputDimensions * PaddedInputDimensions];
};
} // namespace Stockfish::Eval::NNUE::Layers
#endif // #ifndef NNUE_LAYERS_AFFINE_TRANSFORM_H_INCLUDED
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