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/****************************************************************************** | ||
* Copyright (c) 2011-2023, NVIDIA CORPORATION. All rights reserved. | ||
* | ||
* Redistribution and use in source and binary forms, with or without | ||
* modification, are permitted provided that the following conditions are met: | ||
* * Redistributions of source code must retain the above copyright | ||
* notice, this list of conditions and the following disclaimer. | ||
* * Redistributions in binary form must reproduce the above copyright | ||
* notice, this list of conditions and the following disclaimer in the | ||
* documentation and/or other materials provided with the distribution. | ||
* * Neither the name of the NVIDIA CORPORATION nor the | ||
* names of its contributors may be used to endorse or promote products | ||
* derived from this software without specific prior written permission. | ||
* | ||
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND | ||
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED | ||
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE | ||
* DISCLAIMED. IN NO EVENT SHALL NVIDIA CORPORATION BE LIABLE FOR ANY | ||
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES | ||
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; | ||
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND | ||
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | ||
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS | ||
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | ||
* | ||
******************************************************************************/ | ||
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#include <cub/device/device_scan.cuh> | ||
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#include <thrust/device_vector.h> | ||
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#include <iostream> | ||
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template <class ScanTileStateT> | ||
__global__ void init_kernel(ScanTileStateT tile_state, int blocks_in_grid) | ||
{ | ||
tile_state.InitializeStatus(blocks_in_grid); | ||
} | ||
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template <class MessageT> | ||
__global__ void decoupled_look_back_kernel(cub::ScanTileState<MessageT> tile_state) | ||
{ | ||
using scan_op_t = cub::Sum; | ||
using scan_tile_state_t = cub::ScanTileState<MessageT>; | ||
using tile_prefix_op = cub::TilePrefixCallbackOp<MessageT, scan_op_t, scan_tile_state_t>; | ||
using temp_storage_t = typename tile_prefix_op::TempStorage; | ||
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// Allocate temp storage in shared memory | ||
__shared__ temp_storage_t temp_storage; | ||
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scan_op_t scan_op{}; | ||
const unsigned int threads_in_warp = 32; | ||
const unsigned int tid = threadIdx.x; | ||
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// Construct prefix op | ||
tile_prefix_op prefix(tile_state, temp_storage, scan_op); | ||
const unsigned int tile_idx = prefix.GetTileIdx(); | ||
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// Compute block aggregate | ||
MessageT block_aggregate = blockIdx.x; | ||
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if (tile_idx == 0) | ||
{ | ||
// There are no blocks to look back to, immediately set the inclusive state | ||
if (tid == 0) | ||
{ | ||
tile_state.SetInclusive(tile_idx, block_aggregate); | ||
printf("tile %d: inclusive = %d\n", tile_idx, block_aggregate); | ||
} | ||
} | ||
else | ||
{ | ||
// Only the first warp in the block can perform the look back | ||
const unsigned int warp_id = tid / threads_in_warp; | ||
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if (warp_id == 0) | ||
{ | ||
// Perform the decoupled look-back | ||
// Invocation of the prefix will block until the look-back is complete. | ||
MessageT exclusive_prefix = prefix(block_aggregate); | ||
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if (tid == 0) | ||
{ | ||
MessageT inclusive_prefix = scan_op(exclusive_prefix, block_aggregate); | ||
printf("tile %d: exclusive = %d inclusive = %d\n", | ||
tile_idx, | ||
exclusive_prefix, | ||
inclusive_prefix); | ||
} | ||
} | ||
} | ||
} | ||
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template <class MessageT> | ||
void decoupled_look_back_example(int blocks_in_grid) | ||
{ | ||
using scan_tile_state_t = cub::ScanTileState<MessageT>; | ||
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// Query temporary storage requirements | ||
std::size_t temp_storage_bytes{}; | ||
scan_tile_state_t::AllocationSize(blocks_in_grid, temp_storage_bytes); | ||
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// Allocate temporary storage | ||
thrust::device_vector<std::uint8_t> temp_storage(temp_storage_bytes); | ||
std::uint8_t *d_temp_storage = thrust::raw_pointer_cast(temp_storage.data()); | ||
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// Initialize temporary storage | ||
scan_tile_state_t tile_status; | ||
tile_status.Init(blocks_in_grid, d_temp_storage, temp_storage_bytes); | ||
const unsigned int threads_in_init_block = 256; | ||
const unsigned int blocks_in_init_grid = cub::DivideAndRoundUp(blocks_in_grid, | ||
threads_in_init_block); | ||
init_kernel<<<blocks_in_init_grid, threads_in_init_block>>>(tile_status, blocks_in_grid); | ||
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// Launch decoupled look-back | ||
const unsigned int threads_in_block = 256; | ||
decoupled_look_back_kernel<<<blocks_in_grid, threads_in_block>>>(tile_status); | ||
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// Wait for kernel to finish | ||
cudaDeviceSynchronize(); | ||
} | ||
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int main() { decoupled_look_back_example<int>(14); } |