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* dynamically adjust the number of threads

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* disbale parallelisation if we already are in a parallel session
This commit is contained in:
Gael Guennebaud 2010-03-05 10:44:31 +01:00
parent dd961f8c60
commit 48d0595c29
1 changed files with 19 additions and 3 deletions
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22
Eigen/src/Core/products/Parallelizer.h
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@ -44,8 +44,24 @@ void ei_parallelize_gemm(const Functor& func, int rows, int cols)
func(0,rows, 0,cols); func(0,rows, 0,cols);
#else #else
int threads = omp_get_max_threads(); // Dynamically check whether we should enable or disable OpenMP.
if((!Condition)||(threads==1)) // The conditions are:
// - the max number of threads we can create is greater than 1
// - we are not already in a parallel code
// - the sizes are large enough
// 1- are we already in a parallel session?
if((!Condition) || (omp_get_num_threads()>1))
return func(0,rows, 0,cols);
// 2- compute the maximal number of threads from the size of the product:
// FIXME this has to be fine tuned
int max_threads = std::max(1,rows / 32);
// 3 - compute the number of threads we are going to use
int threads = std::min(omp_get_max_threads(), max_threads);
if(threads==1)
return func(0,rows, 0,cols); return func(0,rows, 0,cols);
int blockCols = (cols / threads) & ~0x3; int blockCols = (cols / threads) & ~0x3;
@ -56,7 +72,7 @@ void ei_parallelize_gemm(const Functor& func, int rows, int cols)
GemmParallelInfo<BlockBScalar>* info = new GemmParallelInfo<BlockBScalar>[threads]; GemmParallelInfo<BlockBScalar>* info = new GemmParallelInfo<BlockBScalar>[threads];
#pragma omp parallel for schedule(static,1) #pragma omp parallel for schedule(static,1) num_threads(threads)
for(int i=0; i<threads; ++i) for(int i=0; i<threads; ++i)
{ {
int r0 = i*blockRows; int r0 = i*blockRows;