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Compilers and Tools


KNL Compilers and Tools

The Knight's Landing CPUs are true x86 CPUs, supporting SSE, AVX, AVX2 instructions as well as AVX-512. Correspondingly code compiled for more or less any x86 system with say the GNU compiler collection will function. However, in order to generate code which takes full advantage of AVX-512 a recent compiler is needed, such as GCC or the Intel Compiler Toolchain.

Since the cores on the KNL nodes themselves are weak individually compared to regular Xeon (e.g. Haswell or Sandy Bridge) cores, it is most efficient to use the interactive nodes for compilation. Currently AVX-512 compilation can only take place with the Intel Toolchain. Latest versions of GCC can also generate AVX512.
Intel Parallel Studio
The Intel Parallel Studio XE product is available which includes Intel Composer XE C/C++ and Fortran Compilers. Additionally various libraries (MKL, Threaded Building Blocks) and tools (Intel Advisor, VTune Amplifier XE, Intel MPI, Intel Trace Analyzer and Collector) are included. We discuss these in various sections. We focus here on the Intel C/C++ compiler.

Setting up the Compilers and MPI

The Intel Parallel Studio XE product is installed in:
It comes with set-up scripts that modify user paths to set up the various tools. The single setup script (for Bash) and psxevars.csh (for CSH/TCSH) sets up the product. The scripts should be utilized as follows (Bash version):
source /dist/intel/parallel_studio_xe/parallel_studio_xe/ intel64
For CSH/TCSH one should source the .csh version. The source-ing makes the compilers available for use. The commands are:


the Intel C Compiler


the Intel C++ Compiler


the Intel Fortran Compiler


the MPI Wrapper for the Intel C Compiler


the MPI Wrapper for the Intel C++ Compiler


the MPI Wrapper for the Intel Fortran Compiler

Note: The MPI Wrappers utilize Intel-MPI. There may be caveats when using other MPI Implementations.
Useful Intel C/C++ compiler options
We list below some useful compiler options. For the full documentation please consult: The C/C++ Compiler User and Reference Guide


Select a high level of optimization


Enable OpenMP support


Enable the generation of AVX-512 code

 -qopt-report=level -qopt-report-phase=vec

Generate optimization and vectorization reports. See this note for details on using these options.

C++ and OpenMP Shared Libraries

The intel C/C++ compiler utilized the header files and possibly the C++ Standard library of the installed GCC compilers. Additionally, OpenMP support is provided using shared libraries ( To ensure the compiled C++ codes run we recommend to add the locations of these libraries to the shared library path LD_LIBRARY_PATH.
To do this one should do the following prior to running:
  • source intel64 as described before.
  • add other directories onto the shared library path
  • export LD_LIBRARY_PATH=/dist/<gcc-version>/lib64:/dist/gcc-<version>/lib:/usr/lib64:/usr/lib:$LD_LIBRARY_PATH