MULTINODE ON PBS CLUSTER ENVIRONMENT

This repo contains instructions to launch multinode scripts on a pbs cluster, setting all the ENV_VARIABLES needed for a multi-gpu script with pytorch or pytorch Lightning.

STEPS TO TAKE

1. test.sh: launches the pbs command and set up python script.
2. multinode_scripts/multinode.sh: finds the environment variables to be defined. Also launches the mpirun command from master node. Check line 75 which loades the appropriate module (on my cluster) and the - prefix option of the mpirun command at line 71 (probably need to change it on a different cluster).
3. multinode_scripts/run.sh: Take care of launching the final script on each node, adding the final env variable.

ENV VARIABLES TO BE SET

1. MASTER_ADDR: address of the master node.
2. MASTER_PORT: free communication port on the master node.
3. WORLD_SIZE: total number of processes used (usually num_gpu * num_nodes).
4. NODE_RANK: number rank, different for each node (master is usually 0).

USEFUL RESOURCES

• https://lambdalabs.com/blog/multi-node-pytorch-distributed-training-guide
• https://pytorch-lightning.readthedocs.io/en/stable/clouds/cluster_intermediate_1.html
• https://pytorch-lightning.readthedocs.io/en/stable/advanced/model_parallel.html

USEFUL PBS COMMANDS

• qstat -fQ: see permissions of Queues (e.g. max num of parallel jobs)
• pbsnodes -aSj | grep -F 'gnode' | grep -F 'free': see all free gnode.
• qstat -wan1 -u $user: monitor all launched jobs and requested resources by $user.
• qstat -u $user | grep "$user" | cut -d"." -f1 | xargs qdel: kill all jobs of $user.
• qstat -$user | grep "R" | cut -d"." -f1 | xargs qdel: kill all the running jobs of $user.
• qstat -u $user | grep "Q" | cut -d"." -f1 | xargs qdel: kill all the queued jobs of $user.