Manage job inputs

The core experience of Launch is easily experimenting with different job inputs like hyperparameters and datasets, and routing these jobs to appropriate hardware. Once a job is created, users beyond the original author can adjust these inputs via the W&B GUI or CLI. For information on how job inputs can be set when launching from the CLI or UI, see the Enqueue jobs guide.

This section describes how to programmatically control the inputs that can be tweaked for a job.

By default, W&B jobs capture the entire Run.config as the inputs to a job, but the Launch SDK provides a function to control select keys in the run config or to specify JSON or YAML files as inputs.

Launch SDK functions require wandb-core. See the wandb-core README for more information.

Reconfigure the Run object

The Run object returned by wandb.init in a job can be reconfigured, by default. The Launch SDK provides a way to customize what parts of the Run.config object can be reconfigured when launching the job.

import wandb
from wandb.sdk import launch

# Required for launch sdk use.
wandb.require("core")

config = {
    "trainer": {
        "learning_rate": 0.01,
        "batch_size": 32,
        "model": "resnet",
        "dataset": "cifar10",
        "private": {
            "key": "value",
        },
    },
    "seed": 42,
}


with wandb.init(config=config):
    launch.manage_wandb_config(
        include=["trainer"], 
        exclude=["trainer.private"],
    )
    # Etc.

The function launch.manage_wandb_config configures the job to accept input values for the Run.config object. The optional include and exclude options take path prefixes within the nested config object. This can be useful if, for example, a job uses a library whose options you don’t want to expose to end users.

If include prefixes are provided, only paths within the config that match an include prefix will accept input values. If exclude prefixes are provided, no paths that match the exclude list will be filtered out of the input values. If a path matches both an include and an exclude prefix, the exclude prefix will take precedence.

In the preceding example, the path ["trainer.private"] will filter out the private key from the trainer object, and the path ["trainer"] will filter out all keys not under the trainer object.

Use a \-escaped . to filter out keys with a . in their name.

For example, r"trainer\.private" filters out the trainer.private key rather than the private key under the trainer object.

Note that the r prefix above denotes a raw string.

If the code above is packaged and run as a job, the input types of the job will be:

{
    "trainer": {
        "learning_rate": "float",
        "batch_size": "int",
        "model": "str",
        "dataset": "str",
    },
}

When launching the job from the W&B CLI or UI, the user will be able to override only the four trainer parameters.

Access run config inputs

Jobs launched with run config inputs can access the input values through the Run.config. The Run returned by wandb.init in the job code will have the input values automatically set. Use

from wandb.sdk import launch

run_config_overrides = launch.load_wandb_config()

to load the run config input values anywhere in the job code.

Reconfigure a file

The Launch SDK also provides a way to manage input values stored in config files in the job code. This is a common pattern in many deep learning and large language model use cases, like this torchtune example or this Axolotl config).

Sweeps on Launch does not support the use of config file inputs as sweep parameters. Sweep parameters must be controlled through the Run.config object.

The launch.manage_config_file function can be used to add a config file as an input to the Launch job, giving you access to edit values within the config file when launching the job.

By default, no run config inputs will be captured if launch.manage_config_file is used. Calling launch.manage_wandb_config overrides this behavior.

Consider the following example:

import yaml
import wandb
from wandb.sdk import launch

# Required for launch sdk use.
wandb.require("core")

launch.manage_config_file("config.yaml")

with open("config.yaml", "r") as f:
    config = yaml.safe_load(f)

with wandb.init(config=config):
    # Etc.
    pass

Imagine the code is run with an adjacent file config.yaml:

learning_rate: 0.01
batch_size: 32
model: resnet
dataset: cifar10

The call to launch.manage_config_file will add the config.yaml file as an input to the job, making it reconfigurable when launching from the W&B CLI or UI.

The include and exclude keyword arugments may be used to filter the acceptable input keys for the config file in the same way as launch.manage_wandb_config.

Access config file inputs

When launch.manage_config_file is called in a run created by Launch, launch patches the contents of the config file with the input values. The patched config file is available in the job environment.

Call launch.manage_config_file before reading the config file in the job code to ensure input values are used.

Customize a job’s launch drawer UI

Defining a schema for a job’s inputs allows you to create a custom UI for launching the job. To define a job’s schema, include it in the call to launch.manage_wandb_config or launch.manage_config_file. The schema can either be a python dict in the form of a JSON Schema or a Pydantic model class.

Job input schemas are not used to validate inputs. They are only used to define the UI in the launch drawer.

JSON schema

The following example shows a schema with these properties:

• seed, an integer
• trainer, a dictionary with some keys specified:
  • trainer.learning_rate, a float that must be greater than zero
  • trainer.batch_size, an integer that must be either 16, 64, or 256
  • trainer.dataset, a string that must be either cifar10 or cifar100

schema = {
    "type": "object",
    "properties": {
        "seed": {
          "type": "integer"
        }
        "trainer": {
            "type": "object",
            "properties": {
                "learning_rate": {
                    "type": "number",
                    "description": "Learning rate of the model",
                    "exclusiveMinimum": 0,
                },
                "batch_size": {
                    "type": "integer",
                    "description": "Number of samples per batch",
                    "enum": [16, 64, 256]
                },
                "dataset": {
                    "type": "string",
                    "description": "Name of the dataset to use",
                    "enum": ["cifar10", "cifar100"]
                }
            }
        }
    }
}

launch.manage_wandb_config(
    include=["seed", "trainer"], 
    exclude=["trainer.private"],
    schema=schema,
)

In general, the following JSON Schema attributes are supported:

Attribute	Required	Notes
type	Yes	Must be one of number, integer, string, or object
title	No	Overrides the property’s display name
description	No	Gives the property helper text
enum	No	Creates a dropdown select instead of a freeform text entry
minimum	No	Allowed only if type is number or integer
maximum	No	Allowed only if type is number or integer
exclusiveMinimum	No	Allowed only if type is number or integer
exclusiveMaximum	No	Allowed only if type is number or integer
properties	No	If type is object, used to define nested configurations

Adding a job input schema will create a structured form in the launch drawer, making it easier to launch the job.