Ml Train

ML Training Execution

Execute training runs with proper monitoring, checkpointing, and experiment tracking using PyTorch Lightning and Hydra.

Quick Start

Choose a training template based on your setup:

• Basic single-GPU - Simple training on one GPU
• Multi-GPU single-node - Multiple GPUs on one machine
• Distributed multi-node - Training across multiple machines
• FSDP large models - Very large models with Fully Sharded Data Parallel

Training Commands

Basic training:

python src/train.py

With specific experiment config:

python src/train.py experiment=my_experiment

With CLI overrides:

python src/train.py \
  model.learning_rate=1e-3 \
  data.batch_size=64 \
  trainer.max_epochs=100

Resume from checkpoint:

python src/train.py ckpt_path="checkpoints/epoch_42.ckpt"

Multi-GPU training:

python src/train.py \
  trainer.devices=4 \
  trainer.strategy=ddp

Hyperparameter sweep:

python src/train.py --multirun \
  model.learning_rate=1e-4,1e-3,1e-2 \
  data.batch_size=32,64,128

Pre-Training Checklist

Before starting training, verify:

Environment:

# Check Python version
python --version  # Should be >= 3.10

# Check CUDA availability
python -c "import torch; print(f'CUDA: {torch.cuda.is_available()}, GPUs: {torch.cuda.device_count()}')"

# Check package installation
python -c "import pytorch_lightning as pl; print(f'Lightning: {pl.__version__}')"

# Validate config
python src/train.py --cfg job

# Dry run
python src/train.py trainer.fast_dev_run=5

Disk space:

• Estimate checkpoint storage: model_size_mb × save_top_k × num_epochs / checkpoint_freq
• Ensure logging directory has sufficient space

Experiment tracking:

# Initialize W&B (if using)
wandb login
export WANDB_PROJECT="your-project-name"

# Sync offline runs (if needed)
wandb sync

Monitoring Training

Real-time monitoring:

• Progress bar: Lightning shows metrics automatically
• GPU usage: watch -n 1 nvidia-smi
• W&B dashboard: Metrics, system stats, model graphs

Key metrics to watch:

• Training loss: Should decrease steadily
• Validation loss: Should decrease without diverging from train loss
• Learning rate: Verify scheduler is working
• GPU utilization: Should be >80%
• Training speed: Samples/sec or batches/sec

Red flags:

• Loss is NaN/inf: Check learning rate, add gradient clipping
• Val loss increasing, train decreasing: Overfitting - add regularization
• Very slow training: Check data loading (num_workers), batch size
• Low GPU usage: Increase batch size, check data pipeline
• Out of memory: Reduce batch size, use mixed precision, gradient accumulation

Common Training Issues

Gradient issues:

# Add to trainer config
trainer = Trainer(
    gradient_clip_val=1.0,
    gradient_clip_algorithm="norm",
    track_grad_norm=2,  # Log gradient norms
)

Memory issues:

# Use mixed precision + gradient accumulation
trainer = Trainer(
    precision="16-mixed",
    accumulate_grad_batches=4,
)

# Compile model (PyTorch 2.0+)
model = torch.compile(model)

Slow data loading:

# Profile to identify bottleneck
trainer = Trainer(profiler="simple")

# Optimize data loading
data_module = DataModule(
    num_workers=8,
    pin_memory=True,
    persistent_workers=True,
    prefetch_factor=2,
)

Overfitting:

# Add early stopping
from pytorch_lightning.callbacks import EarlyStopping

trainer = Trainer(
    callbacks=[
        EarlyStopping(monitor="val/loss", patience=10, min_delta=0.001)
    ]
)

# Increase regularization
model:
  dropout: 0.3
  weight_decay: 0.0001

Multi-GPU Strategies

DDP (Distributed Data Parallel):

• Best for: Most use cases, models that fit in single GPU memory
• Usage: trainer.strategy=ddp trainer.devices=4
• Pros: Fast, stable, well-tested
• Cons: Each GPU holds full model copy

FSDP (Fully Sharded Data Parallel):

• Best for: Very large models (>10B parameters)
• Usage: See FSDP template
• Pros: Shard model across GPUs, minimal memory per GPU
• Cons: Slower than DDP, more complex setup

DeepSpeed:

• Best for: Extreme scale (100B+ parameters)
• Usage: trainer.strategy=deepspeed_stage_3
• Pros: Most memory efficient, supports ZeRO optimization
• Cons: Requires additional configuration

Advanced Techniques

Mixed precision training:

python src/train.py trainer.precision=16-mixed

Gradient checkpointing (save memory):

model.gradient_checkpointing_enable()

Learning rate finder:

trainer = Trainer()
lr_finder = trainer.tuner.lr_find(model, datamodule=dm)
fig = lr_finder.plot(suggest=True)

Stochastic Weight Averaging:

from pytorch_lightning.callbacks import StochasticWeightAveraging

trainer = Trainer(callbacks=[StochasticWeightAveraging(swa_lrs=1e-2)])

Post-Training

Load best checkpoint:

best_model_path = trainer.checkpoint_callback.best_model_path
model = MyModel.load_from_checkpoint(best_model_path)

Evaluate on test set:

trainer.test(model, datamodule=dm, ckpt_path="best")

Generate predictions:

predictions = trainer.predict(model, datamodule=dm)

Domain-Specific Training

PyTorch Geometric (GNN Training)

For graph neural networks, see GNN training guide:

# Node classification
python src/train.py \
  model=gnn \
  data=graph \
  data.dataset_name=Cora

# Graph classification with batching
python src/train.py \
  model=gnn \
  data=graph \
  data.dataset_name=PROTEINS \
  data.batch_size=32

# Large graph sampling
python src/train.py \
  model=gnn \
  data=graph \
  data.use_sampling=true \
  data.num_neighbors=[15,10,5]

GNN-specific metrics to monitor:

• Node-level accuracy / Graph-level accuracy
• Over-smoothing (node representations becoming too similar)
• Graph connectivity statistics
• Layer-wise gradient norms

See complete GNN guide for architectures, sampling strategies, and troubleshooting.

Hyperparameter Optimization

Quick Grid Search

python src/train.py --multirun \
  model.learning_rate=1e-4,1e-3,1e-2 \
  data.batch_size=32,64,128

Bayesian Optimization with Optuna

python src/train.py \
  --multirun \
  hydra/sweeper=optuna \
  hydra.sweeper.n_trials=50

For advanced sweep configurations (random search, Bayesian optimization, multi-objective), see reference guide.

W&B Integration

Track Custom Metrics

# In LightningModule
def training_step(self, batch, batch_idx):
    loss = ...

    # Log metrics
    self.log("train/loss", loss)
    self.log("train/acc", accuracy)
    self.log("lr", self.optimizers().param_groups[0]["lr"])

    return loss

Log Artifacts

W&B can automatically log:

• Model checkpoints (log_model=true)
• Confusion matrices
• Sample predictions
• Model graphs

See reference guide for logging confusion matrices, sample predictions, and custom artifacts.

Common Debug Commands

# Quick debug run (5 batches)
python src/train.py trainer.fast_dev_run=5

# Overfit single batch (check model capacity)
python src/train.py trainer.overfit_batches=1 trainer.max_epochs=100

# Profile training (identify bottlenecks)
python src/train.py trainer.profiler=advanced trainer.max_epochs=1

For complete command reference, see reference guide.

Examples

See complete training examples:

• Image classification - CIFAR-10 with ResNet
• Text classification - IMDB with BERT
• Graph neural networks - Node/graph classification with PyTorch Geometric

Troubleshooting

Training doesn't start:

• Check config syntax: python src/train.py --cfg job
• Verify imports: python -c "import pytorch_lightning; import hydra"
• Check CUDA: python -c "import torch; print(torch.cuda.is_available())"

Training is unstable:

• Lower learning rate
• Add gradient clipping
• Check for NaN in data
• Try different optimizer (AdamW → SGD)

Training is slow:

• Profile: trainer.profiler="advanced"
• Check data loading bottleneck
• Increase batch size
• Use mixed precision
• Enable torch.compile() (PyTorch 2.0+)

Success Criteria

• Training starts without errors
• Metrics logged correctly to W&B/TensorBoard
• Checkpoints saved at expected intervals
• Training loss decreases steadily
• Validation metrics improve
• No NaN or inf values in loss
• GPU utilization is high (>80%)
• Training completes or stops early with best model saved

Additional Resources

For advanced topics, see:

• Reference Guide - Hyperparameter sweeps (Optuna, Bayesian), W&B artifacts, environment variables, cloud/HPC training
• GNN Training - PyTorch Geometric specific guide with sampling strategies and architectures
• Image Classification - Complete CIFAR-10 example with ResNet
• Text Classification - Complete IMDB example with BERT

Happy training! 🚀