detectron2_validation_loss_integration.py

# Only 'ADDED NEW' commented statements are added for validation loss calculation.
validation_data_loader = prepare_validation_loader(cfg) # ADDED NEW

logger.info("Starting training from iteration {}".format(start_iter))
with EventStorage(start_iter) as storage:
    for data, iteration in zip(data_loader, range(start_iter, max_iter)):
        storage.iter = iteration

        loss_dict = model(data)
        losses = sum(loss_dict.values())
        assert torch.isfinite(losses).all(), loss_dict
        
        optimizer.zero_grad()
        losses.backward()
        optimizer.step()
        storage.put_scalar("lr", optimizer.param_groups[0]["lr"], smoothing_hint=False)
        scheduler.step()

        calculate_validation_loss(validation_data_loader, model, storage) # ADDED NEW