| 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 <Eigen/Core> |
| |
| 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. |
| |
| */ |
| |
| } |
