HPC Launching Architecture

When configured to perform training on an HPC cluster (cluster configuration resource_manager.type: slurm/pbs), Determined delegates all job scheduling and prioritization to the HPC workload manager (either Slurm or PBS) and does not utilize any Determined Agents. Instead, Determined interfaces with the workload managers via the Determined HPC launcher component.

HPC Launcher

The launcher is a passive server component that translates and forwards Determined master requests to an HPC cluster with a Slurm or PBS workload manager. While it is generally co-located with the Determined master and hosted on an HPC cluster login or admin node, that is not a hard requirement. The launcher interacts with the HPC cluster solely via the Slurm/PBS command line interface and by generated batch scripts and jobs logs on the shared file system. Therefore, it can be hosted on any system that meets these requirements.

HPC Launcher Feature Summary

• Secure, private internal REST interface for use by Determined Master

  • Provides a high-level abstraction to enable Determined to manage Slurm/PBS jobs:

  • Generates the batch script and ancillary files to enable job submission (sbatch, qsub)

  • User-impersonation via a setuid program to enable the configured Determined user agent to submit jobs to the cluster. Existing OS and workload manager permissions, and resource enforcement is maintained. Launcher need not be configured to run as the root user.

  • Job submission and launch failure logs

  • On-demand job status query (sinfo, squery, pbsnodes, qstat)

  • Job cancellation (scancel, qdel)

• Support for various workload managers (Slurm/PBS) and container runtimes (Apptainer/Singularity/Podman/Enroot)

• Provides an image caching model for Apptainer/Singularity

• Minimal state stored solely on the filesystem

Job Management Overview

Temporary files (generated batch files, model python code, startup-hook.sh, etc.), per-rank local directories in each container (/tmp, /run/determined/workdir, etc.), and job log files are all stored under the cluster-wide directory specified via resource_manager.job_storage_root. The lifetime of these files is limited to that of the submitted job, and are removed when job failure or completion is detected by Determined.

1. Determined submits a job to the launcher.

2. A directory tree is created by the launcher for the job.

3. Files provided by Determined are staged.

4. A batch script is generated to describe the required resource request (see Job Resource Scheduling) from the workload manager and context (environment variables, and container launch commands).

5. The ownership of the files is transferred to the launching user (sudo chmod).

6. A setuid image is executed to impersonate the launching user, which in turn executes the sbatch/qsub command to submit the job.

7. Upon being scheduled by the workload manager, the batch script is executed and tasks are launched on the allocated compute nodes.

   1. One Determined environment image is started per node (srun, pbs_tmrsh) using the specified container runtime (Apptainer, Singularity, Podman, Enroot).

   2. During container initialization, per-rank local directories are configured using soft links (/tmp, /run/determined), and the container stdout/stderr starts streaming output directly to the Determined master.

   3. For distributed training, horovodrun is invoked within the container to distribute work within multiple processes across the containers.

8. Once started, the job ID from the workload manager is displayed in the experiment log.

9. Determined polls the launcher for job status waiting for completion.

10. Determined sends a request to the launcher to clean up the job. File ownership is transferred back to the launcher (sudo chmod) which then deletes all temporary files and logs associated with the job.

Job Resource Scheduling

As noted earlier, when using the HPC launcher, Determined delegates all job scheduling and prioritization to the HPC workload manager (Slurm/PBS). Resource requests are generated into the submitted batch file derived from the following Determined configuration attributes.

Cluster Configuration

The resource_manager section of the cluster configuration contributes the following resource scheduling configuration. See the slurm/pbs section of the cluster configuration reference for the full list of configuration options.

• slot_type: The default slot type (cuda, rocm, cpu) when users request resources from Determined in terms of slots_per_trial. May be overridden per partition/resource pool.

• tres_supported: Indicates if SelectType=select/cons_tres is set in the Slurm configuration.

• gres_supported:

  • For Slurm, it indicates that GresTypes=gpu is set in the Slurm configuration, and nodes with GPUs have properly configured GRES indicating the presence of any GPUs. T

  • For PBS, the ngpus resource can be used to identify the number of GPUs available on a node.

• default_aux_resource_pool: The default resource pool to use for tasks that do not need dedicated compute resources, auxiliary, or systems tasks. Defaults to the Slurm/PBS default partition if no resource pool is specified.

• default_compute_resource_pool: The default resource pool to use for tasks that require compute resources, e.g. GPUs or dedicated CPUs. Defaults to the Slurm/PBS default partition if it has GPU resources and if no resource pool is specified.

• job_project_source: Identifies the source to be used when generating a Slurm Workload Characterization Key (WCKey), or PBS project name.

Experiment Configuration

The experiment contributes the following resource scheduling configuration. See the Experiment Configuration Reference for the full details for these configuration options.

• resource_pool: Identifies the queue/partition to be used.

• slots_per_trial: The number of slots to use for each trial of this experiment.

• slurm:

  • sbatch_args: Array of Slurm options added as #SBATCH options in the generated batch script.

  • slots_per_node: The minimum number of slots required for a node to be scheduled during a trial.

  • gpu_type: The Slurm gres type of the GPU to be injected into any generated --gpus/–gres expressions. By default, no type is specified.

• pbs:

  • pbsbatch_args: Array of PBS options added as #PBS options in the generated batch script.

  • slots_per_node: The minimum number of slots required for a node to be scheduled during a trial.

Slurm Scheduling

All information is passed to Slurm through options in the generated sbatch file. You may identify the location of the generated sbatch file and logs using the Slurm command scontrol show job, and then inspect the content any time prior to job completion. These temporary files are removed upon job termination. On job startup failures a portion of the error log is added to the experiment log to assist in diagnosing the problem.

Common Slurm Options

The following options are generated by Determined and cannot be directly specified by the user. Additional options specified by slurm.sbatch_args will be added to the generated batch file provided that they do not conflict with Determined-controlled settings.

Option	Description
--error --output	Captures error/output logs. On job startup failure, a portion of the error log is added to the experiment log to assist in diagnosing the problem. During normal operation, logs are piped directly to the Determined master and these files are not used.
--job-name	Generated job name of the form det-ai_ followed by the Determined job type (exp, cmd, gc) then an internal HPC launcher unique job id.
--partition	Partition name as determined by the selected resource pool.
--wckey	A value identified by the resource_manager.job_project_source configuration.
--no-requeue	Disable any potential automatic requeue of the job by SLURM. Determined will handle the checkpoint and restart for its experiments.

Slurm Resource Calculations

Resource requirements for Slurm jobs submitted by Determined are generated as per the table below. Users can specify a --gres expression via slurm.sbatch_args as long as it does not reference a GPU resource. All other --gres options from the slurm.sbatch_args will be generated into the generated batch script.

Slot Type	Tres 1	Gres 2	Resulting Slurm Options	Description
cuda rocm	true	true	--gpus= [gpu_type:] slots_per_trial --nodes= 1 - slots_per_trial --tasks-per-node= 1 --gpus-per-task= [gpu_type:] slots_per_node	Slurm determines the number of nodes necessary to allocate the requested GPUs. One container is started per node. Multiple GPUs will be allocated per node when available. If slots_per_node is specified, it is added as --gpus_per_task to ensure each node has at least the specified number of GPUs.
cuda rocm	false	true	--nodes= slots_per_trial/slots_per_node --ntasks= slots_per_trial/slots_per_node --gres=gpu [:gpu_type]:slots_per_node	Allocates the calculated slots_per_trial / slots_per_node nodes, and slots_per_node GPUs per node and starts one container per node.
cpu	n/a	n/a	--nodes= slots_per_trial/slots_per_node --ntasks= slots_per_trial/slots_per_node --cpus-per-task= slots_per_node	Allocates the calculated slots_per_trial / slots_per_node nodes, and slots_per_node CPUs per node and starts one container per node. If specified, slots_per_node is add as --cpus_per_task to ensure we get nodes with the desired number of CPUs per node.
cuda rocm	false	false	--nodes= slots_per_trial/slots_per_node --ntasks= slots_per_trial/slots_per_node	Allocates the calculated slots_per_trial / slots_per_node nodes, and slots_per_node GPUs per node and starts one container per node. It is the user’s responsibility to ensure that slots_per_node GPUs will be available on the nodes selected for the job using other configurations such as targeting a specific resource pool with only slots_per_node GPU nodes or specifying a Slurm constraint in the experiment configuration.

1

The tres_supported option of the cluster configuration resource_manager.type: slurm.

2

The gres_supported option of the cluster configuration resource_manager.type: slurm.

Slurm Task Distribution

Distribution of tasks among the nodes allocated by Slurm is accomplished using the Slurm srun command within the generated sbatch file (no special options are required). Environment variables from the experiment configuration and all variables needed by Determined are exported from the generated sbatch file. For those container platforms that do not inherit environment variables by default, each variable is explicitly passed to the container via command line arguments.

PBS Scheduling

All information is passed to PBS through options in the generated PBS batch file. You may identify the location of the generated PBS batch file and logs using the command qstat -f, and then inspect the content any time prior to job completion. These temporary files are removed upon job termination. On job startup failure, a portion of the error log is added to the experiment log to assist in diagnosing the problem.

Common PBS Options

The following options are generated by Determined and cannot be directly specified by the user. Additional options specified by pbs.pbsbatch_args will be added to the generated batch file provided that they do not conflict with Determined-controlled settings.

Option	Description
-N	Generated job name of the form det-ai_ followed by the Determined job type (exp_#_trial, cmd, or gc) then an internal HPC launcher unique job identifier. Example: det-ai_exp-2-trial-2-f53889084a0b4510-b19cc33ba8a50203
-q	Queue name as determined by the selected resource pool.
-e -o	Captures error/output logs. On job startup failures a portion of the error log is added to the experiment log to assist in diagnosing the problem. During normal operation, logs are piped directly to the Determined master and these files are not used.
--V	Inherit environment variables.
-r n	No automatic restart of the job. Allow Determined to handle restarts.
-W umask=0022	Allows the HPC launcher to read the error/output logs.
-P	A value identified by the resource_manager.job_project_source configuration.

PBS Resource Calculations

Resource requirements for PBS jobs submitted by Determined are generated as per the table below. Users can specify a -l select expression via pbs.pbsbatch_args, however chunk count, chunk arrangement, and GPU or CPU counts per chunk (depending on the value of slot_type) are controlled by Determined; any values specified for these quantities will be ignored. All other resource requests from the pbs.pbsbatch_args will be appended to the select expression generated into the generated batch script.

Slot Type	Gres 3	Resulting PBS Options	Description
cuda rocm	true	#PBS -l select= slots_per_trial / slots_per_node :ngpus= slots_per_node	The calculated slots_per_trial/slots_per_node GPUs are allocated, One container is started per node (manually implemented via the generated PBS batch script). Multiple nodes are used when needed. If slots_per_node is not specified, 1 is used in the calculation.
cuda rocm	false	#PBS -l select= slots_per_trial / slots_per_node	The calculated slots_per_trial/slots_per_node GPUs are allocated. It is the user’s responsibility to ensure that``slots_per_node`` GPUs will be available on nodes selected for the job using other configurations such as targeting a specific resource pool with only slots_per_node GPU nodes, or specifying a PBS PBS resource request in the experiment configuration. It is up to the user to set the CUDA_VISIBLE_DEVICES environment variable in their experiment.
cpu	n/a	#PBS -l select= slots_per_trial / slots_per_node :ncpus= slots_per_node	Allocates the calculated slots_per_trial/slots_per_node nodes, and slots_per_node CPUs per node. If slots_per_node is not specified, 1 is used in the calculation.

3

The gres_supported option of the cluster configuration resource_manager.type: pbs.

PBS Task Distribution

The distribution of tasks among the nodes allocated by PBS is accomplished by custom support in the generated batch file. For each unique host in the $PBS_NODEFILE, an asynchronous pbs_tmrsh command invocation is generated to launch the task on the node to launch the specified container and arguments. The batch script waits for the completion of those processes before exiting. A non-zero status return from any of those invocations causes the entire job to be terminated.

Environment variables from the experiment configuration and all variables needed by Determined are explicitly passed to the container as arguments as there is no environment variable inheritance from the PBS batch script to the containers on the nodes.