From b9f25ee656b5b5c4aec6975f3296a1cb10ceea87 Mon Sep 17 00:00:00 2001 From: Gael Guennebaud Date: Thu, 14 Jun 2012 14:24:15 +0200 Subject: bug #466: better fix for the race condition: this new patch add an initParallel() function which must be called at the initialization time of any multi-threaded application calling Eigen from multiple threads. --- doc/TopicMultithreading.dox | 46 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) create mode 100644 doc/TopicMultithreading.dox (limited to 'doc/TopicMultithreading.dox') diff --git a/doc/TopicMultithreading.dox b/doc/TopicMultithreading.dox new file mode 100644 index 000000000..f7d082668 --- /dev/null +++ b/doc/TopicMultithreading.dox @@ -0,0 +1,46 @@ +namespace Eigen { + +/** \page TopicMultiThreading Eigen and multi-threading + +\section TopicMultiThreading_MakingEigenMT Make Eigen run in parallel + +Some Eigen's algorithms can exploit the multiple cores present in your hardware. To this end, it is enough to enable OpenMP on your compiler, for instance: + * 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: +\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 +You can query the number of threads that will be used with: +\code +n = Eigen::nbThreads(n); +\endcode +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 + +\section TopicMultiThreading_UsingEigenWithMT Using Eigen in a multi-threaded application + +In the case your own application is multithreaded, and multiple threads make calls to Eigen, then you have to initialize Eigen by calling the following routine \b before creating the threads: +\code +#include + +int main(int argc, char** argv) +{ + Eigen::initParallel(); + + ... +} +\endcode + +In the case your application is parallelized with OpenMP, you might want to disable Eigen's own parallization as detailed in the previous section. + +*/ + +} -- cgit v1.2.3