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omptexample.cpp
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omptexample.cpp
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/*
* OpDiLib, an Open Multiprocessing Differentiation Library
*
* Copyright (C) 2020-2022 Chair for Scientific Computing (SciComp), TU Kaiserslautern
* Copyright (C) 2023-2024 Chair for Scientific Computing (SciComp), University of Kaiserslautern-Landau
* Homepage: https://scicomp.rptu.de
* Contact: Prof. Nicolas R. Gauger ([email protected])
*
* Lead developer: Johannes Blühdorn (SciComp, University of Kaiserslautern-Landau)
*
* This file is part of OpDiLib (https://scicomp.rptu.de/software/opdi).
*
* OpDiLib is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later
* version.
*
* OpDiLib is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
* details.
*
* You should have received a copy of the GNU Lesser General Public License along with OpDiLib. If not, see
* <http://www.gnu.org/licenses/>.
*
*/
#include <codi.hpp>
#include <iostream>
#include <opdi/backend/ompt/omptBackend.hpp>
#include <opdi.hpp>
using Real = codi::RealReverseIndexOpenMP; // use a suitable CoDiPack type
using Tape = typename Real::Tape;
int main(int nargs, char** args) {
// initialize OpDiLib
if (omp_get_num_threads() /* trigger OMPT initialization */ && opdi::backend == nullptr) {
std::cout << "Could not initialize OMPT backend. Please check OMPT support." << std::endl;
exit(1);
}
opdi::logic = new opdi::OmpLogic;
opdi::logic->init();
opdi::tool = new CoDiOpDiLibTool<Real>;
opdi::tool->init();
// usual AD workflow
Real x = 4.0;
Tape& tape = Real::getTape();
tape.setActive();
tape.registerInput(x);
// parallel computation
size_t constexpr N = 10000000;
Real y = 0.0;
#pragma omp parallel
{
Real localSum = 0.0;
#pragma omp for
for (size_t i = 0; i < N; ++i)
{
localSum += sin(x * i);
}
#pragma omp critical
{
y += localSum;
}
}
// usual AD workflow
tape.registerOutput(y);
tape.setPassive();
y.setGradient(1.0);
opdi::logic->prepareEvaluate(); // prepare OpDiLib for evaluation
tape.evaluate();
std::cout << "f(" << x << ") = " << y << std::endl;
std::cout << "df/dx(" << x << ") = " << x.getGradient() << std::endl;
// finalize OpDiLib
opdi::tool->finalize();
opdi::logic->finalize();
opdi::backend->finalize();
delete opdi::tool;
delete opdi::logic;
return 0;
}
// don't forget to include the OpDiLib source file
#include "opdi.cpp"