Developer Guide

Contents

Using a Custom Message-Passing Interface

While different message-passing interface (MPI) libraries are compatible at the application programming interface (API) level, they are often incompatible at the application binary interface (ABI) level. Therefore,
Intel® oneAPI Math Kernel Library
provides a set of prebuilt BLACS libraries that support certain MPI libraries, but this, however, does not enable use of
Intel® oneAPI Math Kernel Library
with other MPI libraries. To fill this gap,
Intel® oneAPI Math Kernel Library
also includes the MKL MPI wrapper, which provides an MPI-independent ABI to
Intel® oneAPI Math Kernel Library
. The adaptor is provided as source code. To use
Intel® oneAPI Math Kernel Library
with an MPI library that is not supported by default, you can use the adapter to build custom static or dynamic BLACS libraries and use them similarly to the prebuilt libraries.

Building a Custom BLACS Library

The MKL MPI wrapper is located in the
<mkl directory>
\
interfaces
\
mklmpi
directory.
To build a custom BLACS library, from the above directory run the
nmake
command.
For example: the command
n
make libintel64
builds a static custom BLACS library
mkl_blacs_custom_lp64.
lib
using the
default MPI compiler on your system
. Look into the
<mkl directory>
\
interfaces
\
mklmpi
\
makefile
for targets and variables that define how to build the custom library. In particular, you can specify the compiler through the
MPICC
variable.
For more control over the building process, refer to the documentation available through the command
n
make help

Using a Custom BLACS Library

In the case of static linking, use
custom BLACS libraries exactly the same way as you use the prebuilt BLACS libraries, but pass the custom library to the linker. For example, instead of passing the
mkl_blacs_intelmpi_lp64.
lib
static
library, pass
mkl_blacs_custom_lp64.
lib
.
To use a dynamic custom BLACS library:
  1. Link your application the same way as when you use the prebuilt BLACS library.
  2. Call the
    mkl_set_mpi
    support function or set the
    MKL_BLACS_MPI
    environment variable to one of the following values:
    • CUSTOM
      to load a custom library with the default name
      mkl_blacs_custom_lp64.dll
      or
      mkl_blacs_custom_ilp64.dll
      , depending on whether the BLACS interface linked against your application is LP64 or ILP64.
    • <dll_name>
      to load the specified BLACS DLL.
      Intel® oneAPI Math Kernel Library
      looks for the specified DLL either in the directory with
      Intel® oneAPI Math Kernel Library
      dynamic libraries or in the directory with the application executable.
      For a description of the
      mkl_set_mpi
      function, see the
      Intel® oneAPI Math Kernel Library
      Developer Reference
      .

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.