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BlockSelectKernel.cuh
1 /**
2 * Copyright (c) 2015-present, Facebook, Inc.
3 * All rights reserved.
4 *
5 * This source code is licensed under the BSD+Patents license found in the
6 * LICENSE file in the root directory of this source tree.
7 */
8
9 // Copyright 2004-present Facebook. All Rights Reserved.
10 #pragma once
11
12 #include "Float16.cuh"
13 #include "Select.cuh"
14
15 namespace faiss { namespace gpu {
16
17 template <typename K,
18 typename IndexType,
19 bool Dir,
20 int NumWarpQ,
21 int NumThreadQ,
22 int ThreadsPerBlock>
23 __global__ void blockSelect(Tensor<K, 2, true> in,
24 Tensor<K, 2, true> outK,
25 Tensor<IndexType, 2, true> outV,
26 K initK,
27 IndexType initV,
28 int k) {
29 constexpr int kNumWarps = ThreadsPerBlock / kWarpSize;
30
31 __shared__ K smemK[kNumWarps * NumWarpQ];
32 __shared__ IndexType smemV[kNumWarps * NumWarpQ];
33
34 BlockSelect<K, IndexType, Dir, Comparator<K>,
35 NumWarpQ, NumThreadQ, ThreadsPerBlock>
36 heap(initK, initV, smemK, smemV, k);
37
38 // Grid is exactly sized to rows available
39 int row = blockIdx.x;
40
41 int i = threadIdx.x;
42 K* inStart = in[row][i].data();
43
44 // Whole warps must participate in the selection
45 int limit = utils::roundDown(in.getSize(1), kWarpSize);
46
47 for (; i < limit; i += ThreadsPerBlock) {
48 heap.add(*inStart, (IndexType) i);
49 inStart += ThreadsPerBlock;
50 }
51
52 // Handle last remainder fraction of a warp of elements
53 if (i < in.getSize(1)) {
54 heap.addThreadQ(*inStart, (IndexType) i);
55 }
56
57 heap.reduce();
58
59 for (int i = threadIdx.x; i < k; i += ThreadsPerBlock) {
60 outK[row][i] = smemK[i];
61 outV[row][i] = smemV[i];
62 }
63 }
64
65 void runBlockSelect(Tensor<float, 2, true>& in,
66 Tensor<float, 2, true>& outKeys,
67 Tensor<int, 2, true>& outIndices,
68 bool dir, int k, cudaStream_t stream);
69
70 #ifdef FAISS_USE_FLOAT16
71 void runBlockSelect(Tensor<half, 2, true>& in,
72 Tensor<half, 2, true>& outKeys,
73 Tensor<int, 2, true>& outIndices,
74 bool dir, int k, cudaStream_t stream);
75 #endif
76
77 } } // namespace