model/train.py

from transformers import TrainingArguments, Trainer
import torch
from datasets import DatasetDict
from crop_disease_monitor.datasets import load_disease_dataset
from crop_disease_monitor.transforms import build_transforms
from crop_disease_monitor.model.architecture import DiseaseModel

def compute_metrics(eval_pred):
    logits, labels = eval_pred
    preds = logits.argmax(-1)
    acc = (preds == labels).astype(float).mean()
    return {"accuracy": acc}


def main():
    # Load data
    train_ds, val_ds = load_disease_dataset()

    # Build transforms
    transforms = build_transforms()
    def preprocess(batch):
        imgs = [transforms(img.convert("RGB")) for img in batch["image"]]
        return {"pixel_values": imgs, "labels": batch["label"]}

    train_ds = train_ds.with_transform(preprocess)
    val_ds   = val_ds.with_transform(preprocess)

    ds = DatasetDict({"train": train_ds, "validation": val_ds})

    # Instantiate model
    num_classes = len(train_ds.features["label"].names)
    model = DiseaseModel("google/vit-base-patch16-224-in21k", num_classes)

    # Training arguments
    args = TrainingArguments(
        output_dir="./outputs",
        per_device_train_batch_size=16,
        per_device_eval_batch_size=16,
        num_train_epochs=10,
        evaluation_strategy="epoch",
        save_strategy="epoch",
        learning_rate=3e-5,
    )

    # Trainer
    trainer = Trainer(
        model=model,
        args=args,
        train_dataset=ds["train"],
        eval_dataset=ds["validation"],
        compute_metrics=compute_metrics,
        tokenizer=None  # not needed for image tasks
    )

    # Train
    trainer.train()

if __name__ == "__main__":
    main()