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Diffstat (limited to 'doc/TopicMultithreading.dox')
| -rw-r--r-- | doc/TopicMultithreading.dox | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/doc/TopicMultithreading.dox b/doc/TopicMultithreading.dox index 7db2b0e07..47c9b261f 100644 --- a/doc/TopicMultithreading.dox +++ b/doc/TopicMultithreading.dox @@ -8,13 +8,13 @@ Some Eigen's algorithms can exploit the multiple cores present in your hardware. * GCC: \c -fopenmp * ICC: \c -openmp * MSVC: check the respective option in the build properties. -You can control the number of thread that will be used using either the OpenMP API or Eiegn's API using the following priority: +You can control the number of thread that will be used using either the OpenMP API or Eigen's API using the following priority: \code OMP_NUM_THREADS=n ./my_program omp_set_num_threads(n); Eigen::setNbThreads(n); \endcode -Unless setNbThreads has been called, Eigen uses the number of threads specified by OpenMP. You can restore this bahavior by calling \code setNbThreads(0); \endcode +Unless setNbThreads has been called, Eigen uses the number of threads specified by OpenMP. You can restore this behavior by calling \code setNbThreads(0); \endcode You can query the number of threads that will be used with: \code n = Eigen::nbThreads( ); @@ -22,8 +22,12 @@ n = Eigen::nbThreads( ); You can disable Eigen's multi threading at compile time by defining the EIGEN_DONT_PARALLELIZE preprocessor token. Currently, the following algorithms can make use of multi-threading: - * general matrix - matrix products - * PartialPivLU + - general dense matrix - matrix products + - PartialPivLU + - row-major-sparse * dense vector/matrix products + - ConjugateGradient with \c Lower|Upper as the \c UpLo template parameter. + - BiCGSTAB with a row-major sparse matrix format. + - LeastSquaresConjugateGradient \section TopicMultiThreading_UsingEigenWithMT Using Eigen in a multi-threaded application @@ -39,6 +43,10 @@ int main(int argc, char** argv) } \endcode +\note With Eigen 3.3, and a fully C++11 compliant compiler (i.e., <a href="http://en.cppreference.com/w/cpp/language/storage_duration#Static_local_variables">thread-safe static local variable initialization</a>), then calling \c initParallel() is optional. + +\warning note that all functions generating random matrices are \b not re-entrant nor thread-safe. Those include DenseBase::Random(), and DenseBase::setRandom() despite a call to Eigen::initParallel(). This is because these functions are based on std::rand which is not re-entrant. For thread-safe random generator, we recommend the use of boost::random or c++11 random feature. + In the case your application is parallelized with OpenMP, you might want to disable Eigen's own parallization as detailed in the previous section. */ |