Intel(R) - Computational and Systems Biology at MIT

Managing Performance and Memory 6NOTE. The functions take precedence over the respective environmentvariables.In particular, if in your application, you want Intel MKL to use a givennumber of threads and do not want users of your application to changethis via environment variables, set this number of threads by a call tomkl_set_num_threads(), which will have full precedence over anyenvironment variables set.The example below illustrates the use of the Intel MKL function mkl_set_num_threads()to mimic the Intel MKL 9.x default behavior, that is, running on one thread.Example 6-2Setting the number of threads to one#include #include …mkl_set_num_threads ( 1 );The section further expands on the Intel MKL environment variables for threading control.See the Intel MKL Reference Manual for the detailed description of the threading controlfunctions, their parameters, calling syntax, and more code examples.MKL_DYNAMICThe value of MKL_DYNAMIC is by default set to TRUE, regardless of OMP_DYNAMIC, whosedefault value may be FALSE.MKL_DYNAMIC being TRUE means that Intel MKL will always try to pick what it considers thebest number of threads, up to the maximum specified by the user. MKL_DYNAMIC beingFALSE means that Intel MKL will not deviate from the number of threads the userrequested, unless there are reasons why it has no choice.Notice that setting MKL_DYNAMIC=FALSE does not ensure that Intel MKL will use thenumber of threads that you request. The library may examine the problem and pick adifferent number of threads than the value suggested. For example, if you attempt to do asize 1 matrix-matrix multiply across 8 threads, the library may instead choose to use onlyone thread because it is impractical to use 8 threads in this event.6-9