Resume Runs

Specify how a run should behave in the event that that run stops or crashes. To resume or enable a run to automatically resume, you will need to specify the unique run ID associated with that run for the id parameter:

run = wandb.init(entity="<entity>", \ 
        project="<project>", id="<run ID>", resume="<resume>")

tip

W&B encourages you to provide the name of the W&B Project where you want to store the run.

Pass one of the following arguments to the resume parameter to determine how W&B should respond. In each case, W&B first checks if the run ID already exists.

Argument	Description	Run ID exists	Run ID does not exist	Use case
"must"	W&B must resume run specified by the run ID.	W&B resumes run with the same run ID.	W&B raises an error.	Resume a run that must use the same run ID.
"allow"	Allow W&B to resume run if run ID exists.	W&B resumes run with the same run ID.	W&B initializes a new run with specified run ID.	Resume a run without overriding an existing run.
"never"	Never allow W&B to resume a run specified by run ID.	W&B raises an error.	W&B initializes a new run with specified run ID.

You can also specify resume="auto" to let W&B to automatically try to restart the run on your behalf. However, you will need to ensure that you restart your run from the same directory. See the Enable runs to automatically resume section for more information.

For all the examples below, replace values enclosed within <> with your own.

Resume a run that must use the same run ID

Resume a run that uses the same run ID if it is stopped, crashes or fails. To do so, initialize a run and specify the following:

• Set the resume parameter to "must" (resume="must")
• Provide the run ID of the run that stopped or crashed

The following code snippet shows how to accomplish this with the W&B Python SDK:

run = wandb.init(entity="<entity>", \ 
        project="<project>", id="<run ID>", resume="must")

caution

Unexpected results will occur if multiple processes use the same id concurrently.

For more information on how to manage multiple processes, see the Log distributed training experiments

Resume a run without overriding the existing run

Resume a run that stopped or crashed without overriding the existing run. This is especially helpful if your process doesn't exit successfully. The next time you start W&B, W&B will start logging from the last step.

Set the resume parameter to "allow" (resume="allow") when you initialize a run with W&B. Provide the run ID of the run that stopped or crashed. The following code snippet shows how to accomplish this with the W&B Python SDK:

import wandb

run = wandb.init(entity="<entity>", \ 
        project="<project>", id="<run ID>", resume="allow")

Enable runs to automatically resume

The following code snippet shows how to enable runs to automatically resume with the Python SDK or with environment variables.

W&B Python SDK

The following code snippet shows how to specify a W&B run ID with the Python SDK.

Replace values enclosed within <> with your own:

run = wandb.init(entity="<entity>", \ 
        project="<project>", id="<run ID>", resume="<resume>")

Shell script

The following example shows how to specify the W&B WANDB_RUN_ID variable in a bash script:

run_experiment.sh

RUN_ID="$1"

WANDB_RESUME=allow WANDB_RUN_ID="$RUN_ID" python eval.py

Within your terminal, you could run the shell script along with the W&B run ID. The following code snippet passes the run ID akj172:

sh run_experiment.sh akj172 

info

Automatic resuming only works if the process is restarted on top of the same filesystem as the failed process.

For example, suppose you execute a python script called train.py in a directory called called Users/AwesomeEmployee/Desktop/ImageClassify/training/. Within train.py, the script creates a run that enables automatic resuming. Suppose next that the training script is stopped. To resume this run, you would need to restart your train.py script within Users/AwesomeEmployee/Desktop/ImageClassify/training/ .

tip

If you can not share a filesystem, specify the WANDB_RUN_ID environment variable or pass the run ID with the W&B Python SDK. See the Create a run section in the "What are runs?" page for more information on run IDs.

Resume preemptible Sweeps runs

Automatically requeue interrupted sweep runs. This is particularly useful if you run a sweep agent in a compute environment that is subject to preemption such as a SLURM job in a preemptible queue, an EC2 spot instance, or a Google Cloud preemptible VM.

Use the mark_preempting function to enable W&B to automatically requeue interrupted sweep runs. For example, the following code snippet

run = wandb.init()  # Initialize a run
run.mark_preempting()

The following table outlines how W&B handles runs based on the exit status of the a sweep run.

Status	Behavior
Status code 0	Run is considered to have terminated successfully and it will not be requeued.
Nonzero status	W&B automatically appends the run to a run queue associated with the sweep.
No status	Run is added to the sweep run queue. Sweep agents consume runs off the run queue until the queue is empty. Once the queue is empty, the sweep queue resumes generating new runs based on the sweep search algorithm.