cavis/libnd4j/include/helpers/impl/OmpLaunchHelper.cpp

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/*******************************************************************************
* Copyright (c) 2015-2018 Skymind, Inc.
*
* This program and the accompanying materials are made available under the
* terms of the Apache License, Version 2.0 which is available at
* https://www.apache.org/licenses/LICENSE-2.0.
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
* SPDX-License-Identifier: Apache-2.0
******************************************************************************/
//
// @author raver119@gmail.com, created on 6/30/2018
// @author Yurii Shyrma (iuriish@yahoo.com)
//
#include <OmpLaunchHelper.h>
#include <Environment.h>
#include <templatemath.h>
#ifdef _OPENMP
#include <omp.h>
#endif
namespace nd4j {
////////////////////////////////////////////////////////////////////////////////
OmpLaunchHelper::OmpLaunchHelper(const Nd4jLong N, float desiredNumThreads) {
auto maxItersPerThread = Environment::getInstance()->elementwiseThreshold();
if(N < maxItersPerThread)
_numThreads = 1;
else {
#ifdef _OPENMP
if(desiredNumThreads == -1)
desiredNumThreads = omp_get_max_threads();
else if(desiredNumThreads < 1)
desiredNumThreads = 1;
else
desiredNumThreads = nd4j::math::nd4j_min<int>(omp_get_max_threads(), desiredNumThreads);
#else
desiredNumThreads = nd4j::Environment::getInstance()->maxThreads();
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#endif
_numThreads = nd4j::math::nd4j_min<int>(N / maxItersPerThread, desiredNumThreads);
}
_itersPerThread = N / _numThreads;
_remainder = N % _numThreads; // last thread may contain bigger number of iterations
}
Nd4jLong OmpLaunchHelper::betterSpan(Nd4jLong N) {
return OmpLaunchHelper::betterSpan(N, OmpLaunchHelper::betterThreads(N));
}
Nd4jLong OmpLaunchHelper::betterSpan(Nd4jLong N, Nd4jLong numThreads) {
auto r = N % numThreads;
auto t = N / numThreads;
if (r == 0)
return t;
else {
// breaks alignment
return t + 1;
}
}
int OmpLaunchHelper::betterThreads(Nd4jLong N) {
#ifdef _OPENMP
return betterThreads(N, omp_get_max_threads());
#else
return betterThreads(N, nd4j::Environment::getInstance()->maxThreads());;
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#endif
}
int OmpLaunchHelper::betterThreads(Nd4jLong N, int maxThreads) {
auto t = Environment::getInstance()->elementwiseThreshold();
if (N < t)
return 1;
else {
return static_cast<int>(nd4j::math::nd4j_min<Nd4jLong>(N / t, maxThreads));
}
}
int OmpLaunchHelper::tadThreads(Nd4jLong tadLength, Nd4jLong numTads) {
#ifdef _OPENMP
auto maxThreads = omp_get_max_threads();
#else
auto maxThreads = nd4j::Environment::getInstance()->maxThreads();
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#endif
// if there's only 1 thread allowed - nothing to do here
if (maxThreads <= 1)
return 1;
auto totalLength = tadLength * numTads;
// if array is tiny - no need to spawn any threeds
if (totalLength < Environment::getInstance()->elementwiseThreshold())
return 1;
// by default we're spawning as many threads we can, but not more than number of TADs
return nd4j::math::nd4j_min<int>(numTads, maxThreads);
}
}