In Intel MKL, for the automatic offloaded Level 3 BLAS functions (?GEMM, ?TRMM, ?TRSM), the computation can be divided among host CPU and Xeon Phi coprocessors by either using an environment variable or by calling a function and allow users to override the default work division decided by Intel MKL runtime.
The table below gives a few examples showing how to set and manage the division of work between the host and coprocessor(s).
| Examples | Notes |
| MKL_MIC_Set_Workdivision( MKL_TARGET_MIC, -1, 0.5) |
Offload 50% of computation to all cards. The runtime system decides which cards to use. |
| MKL_MIC_Set_Workdivision( MKL_TARGET_MIC, 0, 0.5) | Offload 50% of computation only to the 1st card. |
| MKL_MIC_Set_Workdivision( MKL_TARGET_MIC, 1, MKL_MIC_AUTO_WORKDIVISION) |
Let the runtime to decide how much work to offload to the 2nd card. |
| MKL_MIC_Set_Workdivision( MKL_TARGET_HOST, 0, 0.5) | Keep 50% of computation on the host, offload the rest to all cards. (In this case the second argument is ignored) |
| MKL_MIC_Get_Workdivision( MKL_TARGET_MIC, 0, &wd) |
Find how much work was specified for the 1st card. |
| MKL_MIC_Get_Device_Count( ) | Find how many cards available on the system. |
Work division can also be controlled using environment variables. See the examples in the table below.
Note that support functions always take precedence over environment variables.
| Examples | Notes |
| MKL_MIC_WORKDIVISION=0.5 | Offload 50% of computation to all cards. The runtime system decides which cards to use. |
| MKL_MIC0_WORKDIVISION=0.5 | Offload 50% of computation only to the 1st card. |
| MKL_MIC1_WORKDIVISION= MIC_AUTO_WORKDIVISION |
Let the runtime to decide how much work to offload to the 2nd card. |
| MKL_HOST_WORKDIVISION=0.5 | Keep 50% of computation on the host, offload the rest to all cards. |
Note: These work division controls work differently for LAPACK functions. For LAPACK functions, any non-zero value of work division is interpreted as 100%.
Please refer other articles related to Intel MKL on Intel Xeon Phi at Intel® Math Kernel Library on the Intel® Xeon Phi™ Coprocessor