Resume a run

Resume a paused or exited W&B Run

Specify how W&B should respond if a run stops or crashes. When you initialize a run you can specify how W&B should respond if the run stops or crashes by passing an argument to the resume parameter. W&B checks if the run ID already exists and responds based on the argument passed to the resume parameter.

The following table outlines the behavior of W&B based on the argument passed to the resume parameter and whether the run ID exists or not.

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. Resumes from last step.	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. Resumes from last step.	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 the run ID.	Raise an error if a run with the specified ID already exists.	W&B initializes a new run with specified run ID.
"auto"	Allow W&B to automatically try to resume run if run ID exists. Restart the run from the same directory as the failed process.	W&B resumes run with the same run ID.	W&B initializes a new run with specified run ID.	Enable runs to automatically resume.

When to use auto vs allow

W&B recommends that you use resume="allow" and specify the specific run ID you want to resume.

The resume="auto" option does not require you to specify a run ID but it can lead to unexpected behavior if you have multiple runs that fail in the same directory or if the file directory structure changes. You must also ensure that you restart the run from the same directory as the failed process when you use resume="auto".

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

Resume a run that must use the same run ID

If a run is stopped, crashes, or fails, you can resume it using the same run ID. 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:

with wandb.init(entity="<entity>", project="<project>", resume="must") as run:
        # Your training code here

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

with wandb.init(entity="<entity>", project="<project>", id="<run ID>", resume="allow") as run:
        # Your training code here

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

Pass auto as an argument to the resume parameter when you initialize a run. Ensure that you restart the run from the same directory as the failed process.

Copy and paste the following code snippet. Replace values enclosed within <> with your own:

with wandb.init(entity="<entity>", project="<project>", id="<run ID>", resume="auto") as run:
        # Your training code here

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=auto 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 

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 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/ .

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 Custom run IDs 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 automatically requeue interrupted sweep runs. For example:

with wandb.init() as 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.