Intel(R) - Computational and Systems Biology at MIT

6 Intel® Math Kernel Library User’s GuideNote also that if Intel MKL is called in a parallel region, it will use only one thread bydefault. If you want the library to use nested parallelism, and thread within a parallelregion is compiled with the same OpenMP compiler as Intel MKL is using, you mayexperiment with setting MKL_DYNAMIC to FALSE and manually increasing the number ofthreads.In general, you should set MKL_DYNAMIC to FALSE only under circumstances that IntelMKL is unable to detect, for example, when nested parallelism is desired where the libraryis called already from a parallel section.MKL_DYNAMIC being TRUE, in particular, provides for optimal choice of the number ofthreads in the following cases:• If the requested number of threads exceeds the number of physical cores (perhapsbecause of hyper-threading), and MKL_DYNAMIC is not changed from its default valueof TRUE, Intel MKL will scale down the number of threads to the number of physicalcores.• If you are able detect the presence of MPI, but cannot determine if it has been called ina thread-safe mode (it is impossible to detect this with MPICH 1.2.x, for instance), andMKL_DYNAMIC has not been changed from its default value of TRUE, Intel MKL will runone thread.MKL_DOMAIN_NUM_THREADSMKL_DOMAIN_NUM_THREADS accepts a string value , which must havethe following format: ::= { } ::= [ * ] ( | | | ) [ * ] ::= ::= MKL_ALL | MKL_BLAS | MKL_FFT | MKL_VML ::= [ * ] ( | |) [ * ] ::= ::= | |In the syntax above, MKL_BLAS indicates the BLAS function domain, MKL_FFT indicatesnon-cluster FFTs, and MKL_VML indicates the Vector Mathematics Library.For example,MKL_ALL 2 : MKL_BLAS 1 : MKL_FFT 46-10