Add python api for expand op. (#13453)

* Add python api for expand op.

* Fix unitest.

* Remove 'out' from arguments and fix code style.

* fix API.spec

* Fix API

* Fix unitest

Author: wanghaoshuang

paddle/fluid/API.spec

@@ -168,6 +168,7 @@ paddle.fluid.layers.stack ArgSpec(args=['x', 'axis'], varargs=None, keywords=Non
 paddle.fluid.layers.pad2d ArgSpec(args=['input', 'paddings', 'mode', 'pad_value', 'data_format', 'name'], varargs=None, keywords=None, defaults=([0, 0, 0, 0], 'constant', 0.0, 'NCHW', None))
 paddle.fluid.layers.unstack ArgSpec(args=['x', 'axis', 'num'], varargs=None, keywords=None, defaults=(0, None))
 paddle.fluid.layers.sequence_enumerate ArgSpec(args=['input', 'win_size', 'pad_value', 'name'], varargs=None, keywords=None, defaults=(0, None))
+paddle.fluid.layers.expand ArgSpec(args=['x', 'expand_times', 'name'], varargs=None, keywords=None, defaults=(None,))
 paddle.fluid.layers.sequence_concat ArgSpec(args=['input', 'name'], varargs=None, keywords=None, defaults=(None,))
 paddle.fluid.layers.data ArgSpec(args=['name', 'shape', 'append_batch_size', 'dtype', 'lod_level', 'type', 'stop_gradient'], varargs=None, keywords=None, defaults=(True, 'float32', 0, VarType.LOD_TENSOR, True))
 paddle.fluid.layers.open_files ArgSpec(args=['filenames', 'shapes', 'lod_levels', 'dtypes', 'thread_num', 'buffer_size', 'pass_num', 'is_test'], varargs=None, keywords=None, defaults=(None, None, 1, None))

python/paddle/fluid/layers/nn.py

@@ -113,6 +113,7 @@
     'pad2d',
     'unstack',
     'sequence_enumerate',
+    'expand',
     'sequence_concat',
 ]
 
@@ -6118,3 +6119,53 @@ def unstack(x, axis=0, num=None):
         attrs={'axis': axis,
                'num': num})
     return outs
+
+
+def expand(x, expand_times, name=None):
+    """Expand operator tiles the input by given times number. You should set times
+    number for each dimension by providing attribute 'expand_times'. The rank of X
+    should be in [1, 6]. Please note that size of 'expand_times' must be the same
+    with X's rank. Following is a using case:
+
+
+    .. code-block:: text
+
+        Input(X) is a 3-D tensor with shape [2, 3, 1]:
+        
+                [
+                   [[1], [2], [3]],
+                   [[4], [5], [6]]
+                ]
+        
+        Attr(expand_times):  [1, 2, 2]
+        
+        Output(Out) is a 3-D tensor with shape [2, 6, 2]:
+        
+                [
+                    [[1, 1], [2, 2], [3, 3], [1, 1], [2, 2], [3, 3]],
+                    [[4, 4], [5, 5], [6, 6], [4, 4], [5, 5], [6, 6]]
+                ]
+        
+    Args:
+        x (Variable): A tensor with rank in [1, 6].
+        expand_times (list|tuple): Expand times number for each dimension.
+
+    Returns:
+        Variable: The expanded variable which is a LoDTensor. After expanding, size of each dimension of Output(Out) is equal to ithe size of the corresponding dimension of Input(X) multiplying the corresponding value given by expand_times.
+
+
+    Examples:
+        .. code-block:: python
+
+            x = fluid.layers.data(name='x', shape=[10], dtype='float32')
+            out = fluid.layers.expand(x=x, expand_times=[1, 2, 2])
+    """
+    helper = LayerHelper('expand', input=x, **locals())
+    dtype = helper.input_dtype(input_param_name='x')
+    out = helper.create_tmp_variable(dtype)
+    helper.append_op(
+        type='expand',
+        inputs={'X': x},
+        outputs={'Out': out},
+        attrs={'expand_times': expand_times})
+    return out

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

@@ -565,6 +565,13 @@ def test_cross_entropy(self):
             out = layers.cross_entropy(x, label, False, 4)
             self.assertIsNotNone(out)
 
+    def test_expand(self):
+        program = Program()
+        with program_guard(program):
+            x = layers.data(name="input", shape=[10], dtype='int32')
+            out = layers.expand(x, [1, 2])
+        print(str(program))
+
 
 if __name__ == '__main__':
     unittest.main()