Intel(R) Math Kernel Library for Linux* OS User's Guide

6 Intel® Math Kernel Library User’s GuideMKL_ALL=2; MKL_BLAS=1; MKL_FFT=4MKL_ALL = 2 MKL_BLAS 1 , MKL_FFT 4MKL_ALL,2: MKL_BLAS 1, MKL_FFT,4 .The global variables MKL_ALL, MKL_BLAS, MKL_FFT, and MKL_VML, as well as theinterface for the Intel MKL threading control functions, can be found in the mkl.h headerfile.Table 6-3 illustrates how values of MKL_DOMAIN_NUM_THREADS are interpreted.Table 6-3Interpretation of MKL_DOMAIN_NUM_THREADS ValuesValue ofMKL_DOMAIN_NUM_THREADSMKL_ALL=4MKL_ALL=1, MKL_BLAS=4MKL_VML = 2InterpretationAll parts of Intel MKL should try four threads. The actual number ofthreads may be still different because of the MKL_DYNAMIC setting orsystem resource issues. The setting is equivalent toMKL_NUM_THREADS = 4.All parts of Intel MKL should try one thread, except for BLAS, which issuggested to try four threads.VML should try two threads. The setting affects no other part of IntelMKL.Be aware that the domain-specific settings take precedence over the overall ones. Forexample, the "MKL_BLAS=4" value of MKL_DOMAIN_NUM_THREADS suggests trying fourthreads for BLAS, regardless of later setting MKL_NUM_THREADS, and a function call"mkl_domain_set_num_threads ( 4, MKL_BLAS );" suggests the same, regardless oflater calls to mkl_set_num_threads().However, a function call with input "MKL_ALL", such as "mkl_domain_set_num_threads(4, MKL_ALL);" is equivalent to "mkl_set_num_threads(4)", and thus it will beoverwritten by later calls to mkl_set_num_threads. Similarly, the environment setting ofMKL_DOMAIN_NUM_THREADS with "MKL_ALL=4" will be overwritten with MKL_NUM_THREADS= 2.Whereas the MKL_DOMAIN_NUM_THREADS environment variable enables you set severalvariables at once, for example, "MKL_BLAS=4,MKL_FFT=2", the corresponding functiondoes not take string syntax. So, to do the same with the function calls, you may need tomake several calls, which in this example are as follows:mkl_domain_set_num_threads ( 4, MKL_BLAS );mkl_domain_set_num_threads ( 2, MKL_FFT );6-12