training-smoke-test

Testing & Quality

This skill should be used when the user asks to "create a verification script", "write a test training run", "make a quick training job", "verify my change with a short run", "launch a smoke test", or wants a small Beaker job to validate that a feature works end-to-end on GPUs. Also triggers when the user mentions creating a modified 190M script to test a specific behavior.

QUICK START

How to use this skill

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Source SKILL.md: https://github.com/allenai/OLMo-core/blob/HEAD/.claude/skills/training-smoke-test/SKILL.md

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Training job smoke test

Create short, single-node training scripts that exercise a specific feature in a real GPU run. These scripts are derived from the 190M base config (src/scripts/train/OLMo3/OLMo-3-190M.py) and train for only ~20 steps with an eval callback to confirm the feature works.

When to use

After implementing a new training feature (parallelism mode, eval type, data pipeline change) that needs GPU validation beyond unit tests.
When a CI test cannot cover the behavior (e.g., multi-GPU distributed features).
To produce a quick smoke-test script that can be launched on Beaker.

Workflow

1. Identify what to verify

Determine the feature under test and what "success" looks like. Examples:

Feature	Success signal
CP perplexity evals	LM evaluator reports CE loss and PPL without error
TP training	Training completes 20 steps, loss decreases
New data mix	Data loader produces batches without errors
New attention backend	Training completes 20 steps with the new backend, no kernel errors

2. Copy and modify the 190M base script

Start from src/scripts/train/OLMo3/OLMo-3-190M.py and place the new script in src/scripts/train/smoketests/.

Key modifications:

File name: <feature>-test.py in src/scripts/train/smoketests/.
Docstring: Describe what is being verified and how to run it.
Duration: Duration.steps(20) — just enough to confirm the feature works.
Batch size: SEQ_LENGTH * 16 — small but enough for distributed training.
Metrics/cancel interval: 5 steps (frequent enough to catch issues early).
Remove unused features: Drop Float8Config, InstanceFilterConfig, CheckpointerCallback, FOR_BENCHMARKING, CHINCHILLA_MULTIPLE, estimate_lr() none of these are needed for a quick verification.
WandB: Keep but set enabled=False.

3. Add the feature-specific config

Depending on what is being verified, add the relevant config. Common patterns:

Context Parallelism (CP):

from olmo_core.train.train_module import TransformerContextParallelConfig

# In train_module_config:
cp_config=TransformerContextParallelConfig.ulysses(degree=2),

Tensor Parallelism (TP):

from olmo_core.train.train_module import TransformerTensorParallelConfig

# In train_module_config:
tp_config=TransformerTensorParallelConfig(degree=2),

New attention backend:

from olmo_core.nn.attention import AttentionBackendName

# In model_config — override the backend selection:
model_config = TransformerConfig.olmo3_190M(
    vocab_size=tokenizer_config.padded_vocab_size(),
    attn_backend=AttentionBackendName.flash_4,  # or .te, .torch, etc.
)

Available backends: torch, flash_2, flash_3, flash_4, te. The base script selects between flash_2 and flash_3 based on GPU type; a verification script can hardcode a specific backend to test it.

PPL evals (LMEvaluator):

from olmo_core.data import NumpyPaddedFSLDatasetConfig
from olmo_core.train.callbacks import LMEvaluatorCallbackConfig

# In trainer_config:
.with_callback(
    "lm_evaluator",
    LMEvaluatorCallbackConfig(
        eval_dataset=NumpyPaddedFSLDatasetConfig.from_data_mix(
            DataMix.v3_small_ppl_validation,
            mix_base_dir=get_root_dir(cli_context.cluster),
            sequence_length=SEQ_LENGTH,
            tokenizer=tokenizer_config,
            work_dir=work_dir,
        ),
        eval_interval=10,
    ),
)

Full recommended evals (PPL + downstream):

trainer_config = trainer_config.with_recommended_evals(
    tokenizer_config, SEQ_LENGTH, cli_context.cluster, task_set="fast"
)

Note: downstream evals require full logits and are incompatible with CP or TP.

4. Launch and verify

Before launching, ask the user what priority to use for the Beaker job. The options are: low, normal, high, urgent. Not all workspaces support all priorities (e.g., ai2/OLMo_3 caps at normal).

# Dry run first to check the config renders:
python src/scripts/train/smoketests/<feature>-test.py \
    dry_run test-<feature> ai2/jupiter

# Launch on Beaker:
python src/scripts/train/smoketests/<feature>-test.py \
    launch test-<feature> ai2/jupiter \
    --launch.priority=<priority> \
    --launch.follow=false

Always launch with --launch.follow=false (or set --launch.launch_timeout=<seconds> to cap how long to wait). This avoids blocking the terminal indefinitely.

By default the launch command follows the job logs in the terminal until completion, which requires step_soft_timeout and blocks the session. Using follow=false lets the job run asynchronously.

After launching, report the Beaker experiment link to the user so they can monitor the job.

To reconnect to a running job later:

gantry follow <experiment-id>

5. Confirm success

Check the Beaker logs for:

Training steps completing without errors.
Throughput / MFU at expected levels.
Eval metrics being reported (CE loss, PPL for LM evals).
No NCCL or distributed errors.

Naming convention

Scripts live in src/scripts/train/smoketests/ and are named <feature-slug>-test.py.

Examples:

src/scripts/train/smoketests/cp-ppl-eval-test.py
src/scripts/train/smoketests/tp-training-test.py
src/scripts/train/smoketests/cp-tp-combined-test.py
src/scripts/train/smoketests/new-data-mix-test.py
src/scripts/train/smoketests/flash4-attn-test.py