train.py

"""
Fine-tune a lightweight image classifier on rice grain (seed) images.
Dataset: nateraw/rice-image-dataset (5 rice varieties, 75K images)
Model: microsoft/resnet-18 (lightweight, ~11M params)

Usage (with Hugging Face Jobs):
  HF_MODEL_REPO=chaosbee997/rice-seed-classifier python train.py

Or submit via hf_jobs with a10g-large / t4-small GPU.
"""
import os
import numpy as np
from datasets import load_dataset
from transformers import (
    AutoImageProcessor,
    AutoModelForImageClassification,
    TrainingArguments,
    Trainer,
)
from transformers import DefaultDataCollator
from PIL import Image
import evaluate

# ============= CONFIG =============
DATASET_NAME = "nateraw/rice-image-dataset"
MODEL_NAME = "microsoft/resnet-18"
OUTPUT_REPO = os.environ.get("HF_MODEL_REPO", "chaosbee997/rice-seed-classifier")

# ============= LOAD DATASET =============
print(f"Loading dataset: {DATASET_NAME}")
ds = load_dataset(DATASET_NAME)
print(ds)

split_ds = ds["train"].train_test_split(test_size=0.15, stratify_by_column="label", seed=42)
train_ds = split_ds["train"]
val_ds = split_ds["test"]

labels = ds["train"].features["label"].names
num_labels = len(labels)
label2id = {label: i for i, label in enumerate(labels)}
id2label = {i: label for i, label in enumerate(labels)}

print(f"Classes ({num_labels}): {labels}")
print(f"Train: {len(train_ds)} | Val: {len(val_ds)}")

# ============= LOAD PROCESSOR & MODEL =============
print(f"Loading model: {MODEL_NAME}")
processor = AutoImageProcessor.from_pretrained(MODEL_NAME)
model = AutoModelForImageClassification.from_pretrained(
    MODEL_NAME,
    num_labels=num_labels,
    id2label=id2label,
    label2id=label2id,
    ignore_mismatched_sizes=True,
)

# ============= PREPROCESS =============
def transform(example_batch):
    images = []
    for img in example_batch["image"]:
        if isinstance(img, Image.Image):
            if img.mode != "RGB":
                img = img.convert("RGB")
            images.append(img)
        else:
            img = Image.fromarray(np.array(img)).convert("RGB")
            images.append(img)
    inputs = processor(images, return_tensors="pt")
    inputs["labels"] = example_batch["label"]
    return inputs

train_ds.set_transform(transform)
val_ds.set_transform(transform)

# ============= METRICS =============
accuracy = evaluate.load("accuracy")
f1 = evaluate.load("f1")

def compute_metrics(eval_pred):
    predictions, labels = eval_pred
    preds = np.argmax(predictions, axis=1)
    acc = accuracy.compute(predictions=preds, references=labels)
    f1_score = f1.compute(predictions=preds, references=labels, average="weighted")
    return {"accuracy": acc["accuracy"], "f1": f1_score["f1"]}

# ============= TRAINING ARGS =============
args = TrainingArguments(
    output_dir="/tmp/rice-seed-classifier",
    remove_unused_columns=False,
    evaluation_strategy="epoch",
    save_strategy="epoch",
    learning_rate=5e-5,
    per_device_train_batch_size=64,
    per_device_eval_batch_size=64,
    num_train_epochs=5,
    warmup_ratio=0.1,
    logging_strategy="steps",
    logging_steps=50,
    logging_first_step=True,
    disable_tqdm=True,
    load_best_model_at_end=True,
    metric_for_best_model="accuracy",
    seed=42,
    push_to_hub=True,
    hub_model_id=OUTPUT_REPO,
    report_to="trackio",
    run_name="rice_resnet18_lr5e-5_bs64",
    project="grain-classification",
    trackio_space_id=os.environ.get("TRACKIO_SPACE_ID", "chaosbee997/mlintern-grain"),
)

# ============= TRAINER =============
trainer = Trainer(
    model=model,
    args=args,
    train_dataset=train_ds,
    eval_dataset=val_ds,
    compute_metrics=compute_metrics,
    data_collator=DefaultDataCollator(),
    tokenizer=processor,
)

print("Starting training...")
trainer.train()

print("Evaluating...")
metrics = trainer.evaluate()
print(metrics)

print("Pushing to hub...")
trainer.push_to_hub()
print("Done!")