def eval_epoch()

in tools/kd/train_net.py [0:0]
70 lines of code
23 McCabe index (conditional complexity)

def eval_epoch(val_loader, model, val_meter, cur_epoch, cfg, writer=None):
    """
    Evaluate the model on the val set.
    Args:
        val_loader (loader): data loader to provide validation data.
        model (model): model to evaluate the performance.
        val_meter (ValMeter): meter instance to record and calculate the metrics.
        cur_epoch (int): number of the current epoch of training.
        cfg (CfgNode): configs. Details can be found in
            slowfast/config/defaults.py
        writer (TensorboardWriter, optional): TensorboardWriter object
            to writer Tensorboard log.
    """

    # Evaluation mode enabled. The running stats would not be updated.
    model.eval()
    val_meter.iter_tic()

    for cur_iter, (inputs, labels, _, meta) in enumerate(val_loader):
        # Transferthe data to the current GPU device.
        if isinstance(inputs, (list,)):
            for i in range(len(inputs)):
                inputs[i] = inputs[i].cuda(non_blocking=True)
        else:
            inputs = inputs.cuda(non_blocking=True)
        labels = labels.cuda()
        for key, val in meta.items():
            if isinstance(val, (list,)):
                for i in range(len(val)):
                    val[i] = val[i].cuda(non_blocking=True)
            else:
                meta[key] = val.cuda(non_blocking=True)

        if cfg.DETECTION.ENABLE:
            # Compute the predictions.
            preds = model(inputs, meta["boxes"])

            preds = preds.cpu()
            ori_boxes = meta["ori_boxes"].cpu()
            metadata = meta["metadata"].cpu()

            if cfg.NUM_GPUS > 1:
                preds = torch.cat(du.all_gather_unaligned(preds), dim=0)
                ori_boxes = torch.cat(du.all_gather_unaligned(ori_boxes), dim=0)
                metadata = torch.cat(du.all_gather_unaligned(metadata), dim=0)

            val_meter.iter_toc()
            # Update and log stats.
            val_meter.update_stats(preds.cpu(), ori_boxes.cpu(), metadata.cpu())

        else:
            preds, _ = model(inputs)
            preds = preds[0]

            if cfg.DATA.MULTI_LABEL:
                if cfg.NUM_GPUS > 1:
                    preds, labels = du.all_gather([preds, labels])
            else:
                # Compute the errors.
                ks = (1, 5) if cfg.MODEL.NUM_CLASSES >= 5 else (1, 1)
                num_topks_correct = metrics.topks_correct(preds, labels, ks)

                # Combine the errors across the GPUs.
                top1_err, top5_err = [
                    (1.0 - x / preds.size(0)) * 100.0 for x in num_topks_correct
                ]
                if cfg.NUM_GPUS > 1:
                    top1_err, top5_err = du.all_reduce([top1_err, top5_err])

                # Copy the errors from GPU to CPU (sync point).
                top1_err, top5_err = top1_err.item(), top5_err.item()

                val_meter.iter_toc()
                # Update and log stats.
                val_meter.update_stats(
                    top1_err, top5_err, inputs[0].size(0) * cfg.NUM_GPUS
                )
                # write to tensorboard format if available.
                if writer is not None:
                    writer.add_scalars(
                        {"Val/Top1_err": top1_err, "Val/Top5_err": top5_err},
                        global_step=len(val_loader) * cur_epoch + cur_iter,
                    )

            val_meter.update_predictions(preds, labels)

        val_meter.log_iter_stats(cur_epoch, cur_iter)
        val_meter.iter_tic()

    # Log epoch stats.
    val_meter.log_epoch_stats(cur_epoch)
    # write to tensorboard format if available.
    if writer is not None:
        if cfg.DETECTION.ENABLE:
            writer.add_scalars(
                {"Val/mAP": val_meter.full_map}, global_step=cur_epoch
            )
        all_preds_cpu = [
            pred.clone().detach().cpu() for pred in val_meter.all_preds
        ]
        all_labels_cpu = [
            label.clone().detach().cpu() for label in val_meter.all_labels
        ]
        writer.plot_eval(
            preds=all_preds_cpu, labels=all_labels_cpu, global_step=cur_epoch
        )

    val_meter.reset()