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75 lines
2.8 KiB
Plaintext
75 lines
2.8 KiB
Plaintext
/* Copyright (c) 2021, NVIDIA CORPORATION. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of NVIDIA CORPORATION nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* This example shows how to use the clock function to measure the performance
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* of block of threads of a kernel accurately. Blocks are executed in parallel
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* and out of order. Since there's no synchronization mechanism between blocks,
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* we measure the clock once for each block. The clock samples are written to
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* device memory.
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*/
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// This kernel computes a standard parallel reduction and evaluates the
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// time it takes to do that for each block. The timing results are stored
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// in device memory.
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extern "C" __global__ void timedReduction(const float *input, float *output,
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clock_t *timer) {
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// __shared__ float shared[2 * blockDim.x];
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extern __shared__ float shared[];
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const int tid = threadIdx.x;
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const int bid = blockIdx.x;
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if (tid == 0) timer[bid] = clock();
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// Copy input.
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shared[tid] = input[tid];
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shared[tid + blockDim.x] = input[tid + blockDim.x];
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// Perform reduction to find minimum.
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for (int d = blockDim.x; d > 0; d /= 2) {
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__syncthreads();
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if (tid < d) {
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float f0 = shared[tid];
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float f1 = shared[tid + d];
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if (f1 < f0) {
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shared[tid] = f1;
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}
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}
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}
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// Write result.
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if (tid == 0) output[bid] = shared[0];
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__syncthreads();
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if (tid == 0) timer[bid + gridDim.x] = clock();
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}
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