Numerical Libraries

Numerical Libraries#

There are several versions of BLAS (Basic Linear Algebra Subprograms) and LAPACK (Linear Algebra PACKage) numerical libraries installed on the system. There are a number of versions available on ARC3/4, Intel’s Maths Kernel Library (MKL) library, Automatically Tuned Linear Algebra Software (ATLAS) and the original Netlib. All these libraries, aside from Netlib, are optimised to run on the available hardware. Netlib reference versions are only installed for completeness and we advise that you use one of the other implementations wherever possible.

Setting the module environment#

All available modules can be listed via the module avail command. Numerical libraries will be listed under the /apps/Modules/libraries heading. To load a specific library, e.g. MKL:

$ module load mkl

to switch to another version of the libraries, e.g. Atlas:

$ module switch mkl atlas

This will load the appropriate libraries and paths for your chosen compiler and bit environments.

Compiler Flags#

To simplify linking to the various versions of the numerical libraries, loading the modules as described above will also set up customised environment variables, $ARC_LINALG_FFLAGS for use with Fortran and $ARC_LINALG_CFLAGS for C. For the multi-threaded versions of the libraries use $ARC_LINALG_MT_FFLAGS for Fortran and $ARC_LINALG_MT_CFLAGS for C.

Fortran#

For instance, to compile a simple Fortran program, named matmul.f90 with the MKL library, first load the module:

$ module load mkl

and to compile the code, with the default Intel compiler use:

$ ifort -o matmul matmul.f90 $ARC_LINALG_FFLAGS

To switch to the GNU compiler and a different version of the libraries, e.g. ATLAS:

$ module switch intel gnu
$ module switch mkl atlas

To compile and link to the libraries use:

$ gfortran -o matmul matmul.f90 $ARC_LINALG_FFLAGS

C#

To compile a simple C program, named matmul.c with the MKL library, first load the module

$ module load mkl