def evaluate()

in train_reader.py [0:0]


def evaluate(model, dataset, tokenizer, collator, opt):
    sampler = SequentialSampler(dataset)
    dataloader = DataLoader(dataset,
        sampler=sampler,
        batch_size=opt.per_gpu_batch_size,
        drop_last=False,
        num_workers=10,
        collate_fn=collator
    )
    model.eval()
    total = 0
    exactmatch = []
    model = model.module if hasattr(model, "module") else model
    with torch.no_grad():
        for i, batch in enumerate(dataloader):
            (idx, _, _, context_ids, context_mask) = batch

            outputs = model.generate(
                input_ids=context_ids.cuda(),
                attention_mask=context_mask.cuda(),
                max_length=50
            )

            for k, o in enumerate(outputs):
                ans = tokenizer.decode(o, skip_special_tokens=True)
                gold = dataset.get_example(idx[k])['answers']
                score = src.evaluation.ems(ans, gold)
                total += 1
                exactmatch.append(score)

    exactmatch, total = src.util.weighted_average(np.mean(exactmatch), total, opt)
    return exactmatch