tests/python/unittest/test_contrib_io.py

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import mxnet.ndarray as nd
from mxnet.gluon.data.vision.datasets import *
from mxnet.gluon.data.dataloader import *
from mxnet.contrib.io import *
from mxnet.test_utils import *

mx.npx.reset_np()

def test_contrib_DataLoaderIter():
    def test_mnist_batches(batch_size, expected, last_batch='discard'):
        dataset = MNIST(train=False)
        dataloader = DataLoader(dataset, batch_size, last_batch=last_batch)
        test_iter = DataLoaderIter(dataloader)
        batch = next(test_iter)
        assert batch.data[0].shape == (batch_size, 28, 28, 1)
        assert batch.label[0].shape == (batch_size,)
        count = 0
        test_iter.reset()
        for _ in test_iter:
            count += 1
        assert count == expected, "expected {} batches, given {}".format(expected, count)

    num_examples = 10000
    test_mnist_batches(50, num_examples // 50, 'discard')
    test_mnist_batches(31, num_examples // 31, 'discard')
    test_mnist_batches(31, num_examples // 31, 'rollover')
    test_mnist_batches(31, num_examples // 31 + 1, 'keep')


if __name__ == "__main__":
    test_contrib_DataLoaderIter()