add paddle.io.ComposeDataset & paddle.io.ChainDataset (#28311)

* add paddle.io.ComposeDataset & paddle.io.ChainDataset. test=develop

python/paddle/fluid/dataloader/dataset.py

@@ -17,7 +17,10 @@ from __future__ import print_function
 from .. import framework
 import paddle.dataset.common
 
-__all__ = ["Dataset", "IterableDataset", "TensorDataset"]
+__all__ = [
+    "Dataset", "IterableDataset", "TensorDataset", "ComposeDataset",
+    "ChainDataset"
+]
 
 
 class Dataset(object):
@@ -275,3 +278,130 @@ class TensorDataset(Dataset):
 
     def __len__(self):
         return self.tensors[0].shape[0]
+
+
+def to_list(value):
+    if value is None:
+        return value
+    if isinstance(value, (list, tuple)):
+        return list(value)
+    return [value]
+
+
+class ComposeDataset(Dataset):
+    """
+    A Dataset which composes fields of multiple datasets.
+
+    This dataset is used for composing fileds of multiple map-style
+    datasets of same length.
+
+    Args:
+        datasets(list of Dataset): List of datasets to be composed.
+
+    Returns:
+        Dataset: A Dataset which composes fields of multiple datasets.
+
+    Examples:
+
+        .. code-block:: python
+        
+            import numpy as np
+            import paddle
+            from paddle.io import Dataset, ComposeDataset
+
+
+            # define a random dataset
+            class RandomDataset(Dataset):
+                def __init__(self, num_samples):
+                    self.num_samples = num_samples
+
+                def __getitem__(self, idx):
+                    image = np.random.random([32]).astype('float32')
+                    label = np.random.randint(0, 9, (1, )).astype('int64')
+                    return image, label
+                
+                def __len__(self):
+                    return self.num_samples
+
+            dataset = ComposeDataset([RandomDataset(10), RandomDataset(10)])
+            for i in range(len(dataset)):
+                image1, label1, image2, label2 = dataset[i]
+                print(image1)
+                print(label1)
+                print(image2)
+                print(label2)
+            
+    """
+
+    def __init__(self, datasets):
+        self.datasets = list(datasets)
+        assert len(self.datasets) > 0, "input datasets shoule not be empty"
+        for i, dataset in enumerate(self.datasets):
+            assert isinstance(dataset, Dataset), \
+                    "each input dataset should be paddle.io.Dataset"
+            assert not isinstance(dataset, IterableDataset), \
+                    "paddle.io.IterableDataset not supported"
+            if i > 0:
+                assert len(dataset) == len(self.datasets[i-1]), \
+                        "lengths of datasets should be same"
+
+    def __len__(self):
+        return len(self.datasets[0])
+
+    def __getitem__(self, idx):
+        sample = []
+        for dataset in self.datasets:
+            sample.extend(to_list(dataset[idx]))
+        return tuple(sample)
+
+
+class ChainDataset(IterableDataset):
+    """
+    A Dataset which chains multiple iterable-tyle datasets.
+
+    This dataset is used for assembling multiple datasets which should
+    be :code:`paddle.io.IterableDataset`.
+
+    Args:
+        datasets(list of Dataset): List of datasets to be chainned.
+
+    Returns:
+        Dataset: A Dataset which chains fields of multiple datasets.
+
+    Examples:
+
+        .. code-block:: python
+        
+            import numpy as np
+            import paddle
+            from paddle.io import IterableDataset, ChainDataset
+
+
+            # define a random dataset
+            class RandomDataset(IterableDataset):
+                def __init__(self, num_samples):
+                    self.num_samples = num_samples
+
+                def __iter__(self):
+                    for i in range(10):
+                        image = np.random.random([32]).astype('float32')
+                        label = np.random.randint(0, 9, (1, )).astype('int64')
+                        yield image, label
+                
+            dataset = ChainDataset([RandomDataset(10), RandomDataset(10)])
+            for image, label in iter(dataset):
+                print(image, label)
+            
+    """
+
+    def __init__(self, datasets):
+        self.datasets = list(datasets)
+        assert len(self.datasets) > 0, "input datasets shoule not be empty"
+        for i, dataset in enumerate(self.datasets):
+            assert isinstance(dataset, IterableDataset), \
+                    "ChainDataset only support paddle.io.IterableDataset"
+
+    def __iter__(self):
+        for dataset in self.datasets:
+            for sample in dataset:
+                yield sample

python/paddle/fluid/tests/unittests/test_multiprocess_dataloader_dataset.py

@@ -19,9 +19,38 @@ import numpy as np
 
 import paddle
 import paddle.fluid as fluid
-from paddle.io import TensorDataset, DataLoader
+from paddle.io import Dataset, IterableDataset, TensorDataset, \
+        ComposeDataset, ChainDataset, DataLoader
 from paddle.fluid.dygraph.base import to_variable
 
+IMAGE_SIZE = 32
+
+
+class RandomDataset(Dataset):
+    def __init__(self, sample_num):
+        self.sample_num = sample_num
+
+    def __len__(self):
+        return self.sample_num
+
+    def __getitem__(self, idx):
+        np.random.seed(idx)
+        image = np.random.random([IMAGE_SIZE]).astype('float32')
+        label = np.random.randint(0, 9, (1, )).astype('int64')
+        return image, label
+
+
+class RandomIterableDataset(IterableDataset):
+    def __init__(self, sample_num):
+        self.sample_num = sample_num
+
+    def __iter__(self):
+        for i in range(self.sample_num):
+            np.random.seed(i)
+            image = np.random.random([IMAGE_SIZE]).astype('float32')
+            label = np.random.randint(0, 9, (1, )).astype('int64')
+            yield image, label
+
 
 class TestTensorDataset(unittest.TestCase):
     def run_main(self, num_workers, places):
@@ -55,8 +84,56 @@ class TestTensorDataset(unittest.TestCase):
 
     def test_main(self):
         for p in [fluid.CPUPlace(), fluid.CUDAPlace(0)]:
-            for num_workers in [0, 2]:
-                ret = self.run_main(num_workers=num_workers, places=p)
+            self.run_main(num_workers=0, places=p)
+
+
+class TestComposeDataset(unittest.TestCase):
+    def test_main(self):
+        fluid.default_startup_program().random_seed = 1
+        fluid.default_main_program().random_seed = 1
+
+        dataset1 = RandomDataset(10)
+        dataset2 = RandomDataset(10)
+        dataset = ComposeDataset([dataset1, dataset2])
+        assert len(dataset) == 10
+
+        for i in range(len(dataset)):
+            input1, label1, input2, label2 = dataset[i]
+            input1_t, label1_t = dataset1[i]
+            input2_t, label2_t = dataset2[i]
+            assert np.allclose(input1, input1_t)
+            assert np.allclose(label1, label1_t)
+            assert np.allclose(input2, input2_t)
+            assert np.allclose(label2, label2_t)
+
+
+class TestChainDataset(unittest.TestCase):
+    def run_main(self, num_workers, places):
+        fluid.default_startup_program().random_seed = 1
+        fluid.default_main_program().random_seed = 1
+
+        dataset1 = RandomIterableDataset(10)
+        dataset2 = RandomIterableDataset(10)
+        dataset = ChainDataset([dataset1, dataset2])
+
+        samples = []
+        for data in iter(dataset):
+            samples.append(data)
+        assert len(samples) == 20
+
+        idx = 0
+        for image, label in iter(dataset1):
+            assert np.allclose(image, samples[idx][0])
+            assert np.allclose(label, samples[idx][1])
+            idx += 1
+        for image, label in iter(dataset2):
+            assert np.allclose(image, samples[idx][0])
+            assert np.allclose(label, samples[idx][1])
+            idx += 1
+
+    def test_main(self):
+        for p in [fluid.CPUPlace(), fluid.CUDAPlace(0)]:
+            self.run_main(num_workers=0, places=p)
 
 
 if __name__ == '__main__':

python/paddle/io/__init__.py

@@ -17,6 +17,8 @@ __all__ = [
     'Dataset',
     'IterableDataset',
     'TensorDataset',
+    'ComposeDataset',
+    'ChainDataset',
     'BatchSampler',
     'DistributedBatchSampler',
     #            'Transform',
@@ -29,4 +31,5 @@ __all__ = [
 
 from ..fluid.io import DataLoader
 from ..fluid.dataloader import Dataset, IterableDataset, BatchSampler, get_worker_info, \
-        TensorDataset, Sampler, SequenceSampler, RandomSampler, DistributedBatchSampler
+        TensorDataset, Sampler, SequenceSampler, RandomSampler, DistributedBatchSampler, \
+        ComposeDataset, ChainDataset