UCX environment parameters

• Setting the devices to use from the command line.

In order to specify the devices to use for the run, please use the following environment parameters:
UCX_NET_DEVICES
UCX_SHM_DEVICES
UCX_ACC_DEVICES

UCX_NET_DEVICES for specifying the network devices. For example: mlx5_1:1: / mlx5_1:1 / GEMINI
UCX_SHM_DEVICES for specifying the shared memory devices. For example: sysv / knem
UCX_ACC_DEVICES for specifying the acceleration devices. For example: gpu0

The following command line will use the rc_x and mm UCTs and their corresponding devices will be mlx5_0:1 and sysv.
mpirun -mca pml ucx -x UCX_TLS=rc_x,mm -x UCX_NET_DEVICES=mlx5_0:1 -x UCX_SHM_DEVICES=sysv ...

This way, for instance, making the choice for the HCA to use doesn't affect the devices used for the shared memory UCTs.

If one or more of these environment parameters aren't used in the command line, their default values will be used.
The current defaults are 'all', which means to use all the available active ports.
To check the default value of these (as well as all other) environment parameters, please run the following:
./bin/ucx_info -f

For these specific ones:
./bin/ucx_info -f | grep DEVICES
UCX_NET_DEVICES=all
UCX_SHM_DEVICES=all
UCX_ACC_DEVICES=all