example_load.py

#!/usr/bin/env python3
"""
Example script for loading preprocessed LibriBrain MEG data.

This script demonstrates how to load and use the preprocessed MEG data
with the pnpl library for training machine learning models.
"""

import numpy as np
from pnpl.datasets import GroupedDataset
from torch.utils.data import DataLoader
import torch

def load_preprocessed_data(grouping_level=100, load_to_memory=True):
    """
    Load preprocessed LibriBrain MEG data.

    Args:
        grouping_level: Number of samples grouped together (5, 10, 15, 20, 25, 30, 45, 50, 55, 60, or 100)
        load_to_memory: If True, loads entire dataset to memory for faster access

    Returns:
        Tuple of (train_dataset, val_dataset, test_dataset)
    """
    base_path = f"data/grouped_{grouping_level}"

    # Load training data
    train_dataset = GroupedDataset(
        preprocessed_path=f"{base_path}/train_grouped.h5",
        load_to_memory=load_to_memory
    )

    # Load validation data
    val_dataset = GroupedDataset(
        preprocessed_path=f"{base_path}/validation_grouped.h5",
        load_to_memory=load_to_memory
    )

    # Load test data
    test_dataset = GroupedDataset(
        preprocessed_path=f"{base_path}/test_grouped.h5",
        load_to_memory=load_to_memory
    )

    return train_dataset, val_dataset, test_dataset


def main():
    # Example 1: Load data with 100-sample grouping
    print("Loading preprocessed MEG data with 100-sample grouping...")
    train_dataset, val_dataset, test_dataset = load_preprocessed_data(
        grouping_level=100,
        load_to_memory=True
    )

    print(f"Dataset sizes:")
    print(f"  Train: {len(train_dataset)} samples")
    print(f"  Validation: {len(val_dataset)} samples")
    print(f"  Test: {len(test_dataset)} samples")

    # Example 2: Get a single sample
    sample = train_dataset[0]
    meg_data = sample['meg']  # MEG signals: (306 channels, time_points)
    phoneme_label = sample['phoneme']  # Phoneme class index

    print(f"\nSample structure:")
    print(f"  MEG shape: {meg_data.shape}")
    print(f"  Phoneme label: {phoneme_label}")

    # Example 3: Use with PyTorch DataLoader
    print("\nCreating PyTorch DataLoader...")
    dataloader = DataLoader(
        train_dataset,
        batch_size=32,
        shuffle=True,
        num_workers=4,
        pin_memory=True  # For GPU training
    )

    # Example 4: Iterate through a batch
    print("\nExample batch:")
    for batch_idx, batch in enumerate(dataloader):
        meg_batch = batch['meg']  # Shape: (batch_size, 306, time_points)
        phoneme_batch = batch['phoneme']  # Shape: (batch_size,)

        print(f"  Batch {batch_idx}:")
        print(f"    MEG batch shape: {meg_batch.shape}")
        print(f"    Phoneme batch shape: {phoneme_batch.shape}")

        if batch_idx >= 2:  # Show only first 3 batches
            break

    # Example 5: Different grouping levels for different speed/accuracy trade-offs
    print("\n" + "="*50)
    print("Available grouping levels:")
    print("  - grouped_5:   Highest fidelity, largest files")
    print("  - grouped_10:  High fidelity")
    print("  - grouped_20:  Good balance")
    print("  - grouped_50:  Faster loading, moderate averaging")
    print("  - grouped_100: Fastest loading, most averaging")
    print("\nChoose based on your requirements:")
    print("  - For maximum accuracy: use lower grouping (5-20)")
    print("  - For faster experimentation: use higher grouping (50-100)")
    print("  - For production models: start with high grouping for prototyping,")
    print("    then switch to lower grouping for final training")


if __name__ == "__main__":
    main()