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L2Norm.cu
/**
* Copyright (c) 2015-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the CC-by-NC license found in the
* LICENSE file in the root directory of this source tree.
*/
// Copyright 2004-present Facebook. All Rights Reserved.
#include "L2Norm.cuh"
#include "../../FaissAssert.h"
#include "../utils/ConversionOperators.cuh"
#include "../utils/DeviceDefs.cuh"
#include "../utils/DeviceUtils.h"
#include "../utils/Float16.cuh"
#include "../utils/MathOperators.cuh"
#include "../utils/PtxUtils.cuh"
#include "../utils/StaticUtils.h"
#include "../utils/Reductions.cuh"
namespace faiss { namespace gpu {
// Input: (batch x dim), # repeats
// Output: (# repeats, norm of batch vector)
// Done under the presumption that the dimension size is not too large
// (<10k or so), since there wouldn't be enough parallelism applying a
// single block to the problem. Also that each vector is large enough
// (>64), since a single block works on multiple rows' norms at the
// same time.
// T: the type we are doing the math in (e.g., float, half)
// TVec: the potentially vectorized type we are loading in (e.g.,
// float4, half2)
template <typename T, typename TVec,
int RowTileSize, bool NormLoop, bool NormSquared>
__global__ void l2Norm(Tensor<TVec, 2, true> input,
Tensor<T, 1, true> output) {
extern __shared__ char smemByte[]; // #warps * RowTileSize elements
T* smem = (T*) smemByte;
int numWarps = utils::divUp(blockDim.x, kWarpSize);
int laneId = getLaneId();
int warpId = threadIdx.x / kWarpSize;
bool lastRowTile = (blockIdx.x == (gridDim.x - 1));
int rowStart = RowTileSize * blockIdx.x;
T rowNorm[RowTileSize];
if (lastRowTile) {
// We are handling the very end of the input matrix rows
for (int row = 0; row < input.getSize(0) - rowStart; ++row) {
if (NormLoop) {
rowNorm[0] = Math<T>::zero();
for (int col = threadIdx.x; col < input.getSize(1); col += blockDim.x) {
TVec val = input[rowStart + row][col];
val = Math<TVec>::mul(val, val);
rowNorm[0] = Math<T>::add(rowNorm[0], Math<TVec>::reduceAdd(val));
}
} else {
TVec val = input[rowStart + row][threadIdx.x];
val = Math<TVec>::mul(val, val);
rowNorm[0] = Math<TVec>::reduceAdd(val);
}
rowNorm[0] = warpReduceAllSum(rowNorm[0]);
if (laneId == 0) {
smem[row * numWarps + warpId] = rowNorm[0];
}
}
} else {
// We are guaranteed that all RowTileSize rows are available in
// [rowStart, rowStart + RowTileSize)
if (NormLoop) {
// A single block of threads is not big enough to span each
// vector
TVec tmp[RowTileSize];
#pragma unroll
for (int row = 0; row < RowTileSize; ++row) {
rowNorm[row] = Math<T>::zero();
}
for (int col = threadIdx.x; col < input.getSize(1); col += blockDim.x) {
#pragma unroll
for (int row = 0; row < RowTileSize; ++row) {
tmp[row] = input[rowStart + row][col];
}
#pragma unroll
for (int row = 0; row < RowTileSize; ++row) {
tmp[row] = Math<TVec>::mul(tmp[row], tmp[row]);
}
#pragma unroll
for (int row = 0; row < RowTileSize; ++row) {
rowNorm[row] = Math<T>::add(rowNorm[row],
Math<TVec>::reduceAdd(tmp[row]));
}
}
} else {
TVec tmp[RowTileSize];
// A block of threads is the exact size of the vector
#pragma unroll
for (int row = 0; row < RowTileSize; ++row) {
tmp[row] = input[rowStart + row][threadIdx.x];
}
#pragma unroll
for (int row = 0; row < RowTileSize; ++row) {
tmp[row] = Math<TVec>::mul(tmp[row], tmp[row]);
}
#pragma unroll
for (int row = 0; row < RowTileSize; ++row) {
rowNorm[row] = Math<TVec>::reduceAdd(tmp[row]);
}
}
// Sum up all parts in each warp
#pragma unroll
for (int row = 0; row < RowTileSize; ++row) {
rowNorm[row] = warpReduceAllSum(rowNorm[row]);
}
if (laneId == 0) {
#pragma unroll
for (int row = 0; row < RowTileSize; ++row) {
smem[row * numWarps + warpId] = rowNorm[row];
}
}
}
__syncthreads();
// Sum across warps
if (warpId == 0) {
#pragma unroll
for (int row = 0; row < RowTileSize; ++row) {
rowNorm[row] = laneId < numWarps ?
smem[row * numWarps + laneId] : Math<T>::zero();
}
#pragma unroll
for (int row = 0; row < RowTileSize; ++row) {
rowNorm[row] = warpReduceAllSum(rowNorm[row]);
}
// Write out answer
if (laneId == 0) {
#pragma unroll
for (int row = 0; row < RowTileSize; ++row) {
int outCol = rowStart + row;
if (lastRowTile) {
if (outCol < output.getSize(0)) {
output[outCol] =
NormSquared ? rowNorm[row] :
ConvertTo<T>::to(
sqrtf(ConvertTo<float>::to(rowNorm[row])));
}
} else {
output[outCol] =
NormSquared ? rowNorm[row] :
ConvertTo<T>::to(
sqrtf(ConvertTo<float>::to(rowNorm[row])));
}
}
}
}
}
template <typename T, typename TVec>
void runL2Norm(Tensor<T, 2, true>& input,
Tensor<T, 1, true>& output,
bool normSquared,
cudaStream_t stream) {
FAISS_ASSERT(input.getSize(0) == output.getSize(0));
int maxThreads = getMaxThreadsCurrentDevice();
constexpr int rowTileSize = 8;
#define RUN_L2(TYPE_T, TYPE_TVEC, INPUT) \
do { \
if (normLoop) { \
if (normSquared) { \
l2Norm<TYPE_T, TYPE_TVEC, rowTileSize, true, true> \
<<<grid, block, smem, stream>>>(INPUT, output); \
} else { \
l2Norm<TYPE_T, TYPE_TVEC, rowTileSize, true, false> \
<<<grid, block, smem, stream>>>(INPUT, output); \
} \
} else { \
if (normSquared) { \
l2Norm<TYPE_T, TYPE_TVEC, rowTileSize, false, true> \
<<<grid, block, smem, stream>>>(INPUT, output); \
} else { \
l2Norm<TYPE_T, TYPE_TVEC, rowTileSize, false, false> \
<<<grid, block, smem, stream>>>(INPUT, output); \
} \
} \
} while (0)
if (input.template canCastResize<TVec>()) {
// Can load using the vectorized type
auto inputV = input.template castResize<TVec>();
int dim = inputV.getSize(1);
bool normLoop = dim > maxThreads;
int numThreads = min(dim, maxThreads);
auto grid = dim3(utils::divUp(inputV.getSize(0), rowTileSize));
auto block = dim3(numThreads);
auto smem = sizeof(T) * rowTileSize * utils::divUp(numThreads, kWarpSize);
RUN_L2(T, TVec, inputV);
} else {
// Can't load using the vectorized type
int dim = input.getSize(1);
bool normLoop = dim > maxThreads;
int numThreads = min(dim, maxThreads);
auto grid = dim3(utils::divUp(input.getSize(0), rowTileSize));
auto block = dim3(numThreads);
auto smem = sizeof(T) * rowTileSize * utils::divUp(numThreads, kWarpSize);
RUN_L2(T, T, input);
}
#undef RUN_L2
CUDA_VERIFY(cudaGetLastError());
}
void runL2Norm(Tensor<float, 2, true>& input,
Tensor<float, 1, true>& output,
bool normSquared,
cudaStream_t stream) {
runL2Norm<float, float4>(input, output, normSquared, stream);
}
#ifdef FAISS_USE_FLOAT16
void runL2Norm(Tensor<half, 2, true>& input,
Tensor<half, 1, true>& output,
bool normSquared,
cudaStream_t stream) {
runL2Norm<half, half2>(input, output, normSquared, stream);
}
#endif
} } // namespace
faiss::gpu::Math::reduceAdd
static __device__ T reduceAdd(T v)
For a vector type, this is a horizontal add, returning sum(v_i)
Definition: MathOperators.cuh:45