This little example shows how VEO (Vector Engine Offloading) can be used from Fortran. Instead of having all VEO API converted to Fortran, this example implements the VEO calls specific to the program in C and uses them with the help of ISO_C_BINDING.

hello.f03: Fortran main program. Runs on the vector host (VH).

libvehello.f03: Fortran offloaded kernel, supposed to run on the vector engine (VE).

veo_glue_code.c: Specialized code that deals with VEO details and calls the VEO kernel in libvehello.f03. This is in C because the VEO API is in C. The glue code uses static VEO linking because that allows the use of OpenMP insode the VEO kernels. This is currently a limitation of VEO.

veo_glue.f03: Fortran module implementing the interfaces to the functions defined in veo_glue_code.c.

Clone the repository:

git clone https://github.com/efocht/veo-fortran

Build the files (an an Aurora system!):

cd veo-fortran

make

Run the test:

OMP_NUM_THREADS=4 ./hello

The env variable OMP_NUM_THREADS is being passed and used by the VE kernel. You can also specify the VE ID on which the kernel should run:

export VE_NODE_NUMBER=<ve_node_id>