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https://github.com/OPM/opm-simulators.git
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94 lines
3.5 KiB
C++
94 lines
3.5 KiB
C++
/*
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Copyright 2024 SINTEF AS
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This file is part of the Open Porous Media project (OPM).
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OPM is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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OPM is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with OPM. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef OPM_AUTOTUNER_HPP
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#define OPM_AUTOTUNER_HPP
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#include <cuda.h>
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#include <cuda_runtime.h>
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#include <functional>
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#include <limits>
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#include <opm/common/ErrorMacros.hpp>
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#include <opm/common/OpmLog/OpmLog.hpp>
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#include <opm/simulators/linalg/gpuistl/detail/gpu_safe_call.hpp>
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#include <string>
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#include <utility>
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namespace Opm::gpuistl::detail
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{
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/// @brief Function that tests the best thread block size, assumes the provided function depends on threadblock-size
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/// @tparam The type of the function to tune
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/// @param f the function to tune, which takes the thread block size as the input
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template <typename func>
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int
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tuneThreadBlockSize(func& f, std::string descriptionOfFunction)
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{
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// This threadblock-tuner is very simple, it tests all valid block sizes divisble by 64
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// 64 is chosen so it is a multiple of the AMD wavefront size.
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// The maximum size of a threadblock is 1024, so an exhaustive search here will not be expensive
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// We time the kernel with each possible threadblock-size, and return the one
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// that gave the fastest invidivual run.
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// TODO: figure out a more rigorous way of deciding how many runs will suffice?
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constexpr const int runs = 2;
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cudaEvent_t events[runs + 1];
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// create the events
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for (int i = 0; i < runs + 1; ++i) {
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OPM_GPU_SAFE_CALL(cudaEventCreate(&events[i]));
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}
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// Initialize helper variables
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float bestTime = std::numeric_limits<float>::max();
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int bestBlockSize = -1;
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int interval = 64;
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// try each possible blocksize
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for (int thrBlockSize = interval; thrBlockSize <= 1024; thrBlockSize += interval) {
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// record a first event, and then an event after each kernel
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OPM_GPU_SAFE_CALL(cudaEventRecord(events[0]));
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for (int i = 0; i < runs; ++i) {
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f(thrBlockSize); // runs an arbitrary function with the provided arguments
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OPM_GPU_SAFE_CALL(cudaEventRecord(events[i + 1]));
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}
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// make suret he runs are over
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OPM_GPU_SAFE_CALL(cudaEventSynchronize(events[runs]));
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// kernel launch was valid
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if (cudaSuccess == cudaGetLastError()) {
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// check if we beat the record for the fastest kernel
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for (int i = 0; i < runs; ++i) {
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float candidateBlockSizeTime;
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OPM_GPU_SAFE_CALL(cudaEventElapsedTime(&candidateBlockSizeTime, events[i], events[i + 1]));
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if (candidateBlockSizeTime < bestTime) { // checks if this configuration beat the current best
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bestTime = candidateBlockSizeTime;
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bestBlockSize = thrBlockSize;
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}
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}
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}
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}
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OpmLog::info(
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fmt::format("{}: Tuned Blocksize: {} (fastest runtime: {}).", descriptionOfFunction, bestBlockSize, bestTime));
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return bestBlockSize;
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}
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} // end namespace Opm::gpuistl::detail
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#endif
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