F.pad add attribute pad_from_left_axis and improvement 易用性提升

python/paddle/nn/functional/common.py

@@ -1690,25 +1690,38 @@ def pad(
     mode: _PaddingTensorMode = 'constant',
     value: float = 0.0,
     data_format: DataLayoutND = "NCHW",
+    pad_from_left_axis: bool = True,
     name: str | None = None,
 ) -> Tensor:
     """
     Pad tensor according to ``'pad'`` and ``'mode'``.
-    If mode is ``'constant'`` and length of pad is twice as length of x dimension,
-    then the padding will be started from the first dimension and moved back onto x
-    according to ``'pad'`` and ``'value'``.
-    If mode is ``'reflect'``, pad[0] and pad[1] must be no greater
-    than width-1. The height and depth dimension has the same condition.
 
-    Parameters:
-        x (Tensor): The input tensor with data type float32/double/int32/int64_t/complex64/complex128.
-        pad (Tensor|list[int]|tuple[int]): The padding size with data type int.
-            If mode is ``'constant'`` and length of pad is twice as length of x dimension, then x will
-            be padded from the first  dimension to the last dimension.
-            Else: 1. If input dimension is 3, then the pad has the form (pad_left,
-            pad_right). 2. If the input dimension is 4, then the pad has the form (pad_left, pad_right,
-            pad_top, pad_bottom). 3. If the input dimension is 5, then the pad has the form
-            (pad_left, pad_right, pad_top, pad_bottom, pad_front, pad_back).
+    Note:
+        1. Denote ``'x'``'s dimension as N (same in the following). If mode is ``'constant'``, the length
+        of ``'pad'`` can be any even number less than or equal to 2*N.
+
+        2. When mode is ``'constant'``, and ``'pad'`` is a list or tuple, and the length of ``'pad'`` is not
+        equal to 2*(N - 2):
+        2.1. If the length of ``'pad'`` is 2*N, the order of padding can be customized by ``'pad_from_left_axis'``.
+        if ``'pad_from_left_axis'`` is True, then the padding order will be started from the first dimension of
+        ``'x'`` and moving backward according to ``'pad'``; else if ``'pad_from_left_axis'`` is False, then the
+        padding order will be started from the last dimension of ``'x'`` and moving forward according to ``'pad'``.
+        2.2. Otherwise, the padding will be started from the last dimension.
+
+        3. When mode is any of ``'reflect'``, ``'replicate'``, ``'circular'``, or ``'pad'`` is a tensor, or the
+        length of ``'pad'`` is 2*(N - 2), and the dimension of ``'x'`` only supports 3-D, 4-D and 5-D.
+        In these cases, input ``'x'`` will be padded on [D, H, W] axes according to ``'data_format'``. It will pad
+        from the last dimension to the first dimension of [D, H, W] axes.
+        Specifically, if N = 3, then the pad has the form (pad_left, pad_right); if N = 4, then the pad has the form
+        (pad_left, pad_right, pad_top, pad_bottom); if N = 5, then the pad has the form (pad_left, pad_right,
+        pad_top, pad_bottom, pad_front, pad_back).
+
+        4. If mode is ``'reflect'``, pad[0] and pad[1] must be no greater than width-1. The height and depth
+        dimension has the same condition.
+
+    Args:
+        x (Tensor): The input tensor with data type float32, float64, int32, int64, complex64 or complex128.
+        pad (Tensor|list[int]|tuple[int]): The padding size with data type int. Refer to Note for details.
         mode (str, optional): Four modes: ``'constant'`` (default), ``'reflect'``, ``'replicate'``, ``'circular'``. Default is ``'constant'``.
 
            - 'constant' mode, uses a constant value to pad the input tensor.
@@ -1718,8 +1731,12 @@ def pad(
 
         value (float, optional): The value to fill the padded areas in 'constant' mode . Default is :math:`0.0`.
         data_format (str, optional): An string from: ``'NCL'``, ``'NLC'``, ``'NHWC'``, ``'NCHW'``, ``'NCDHW'``, ``'NDHWC'``. Specify the data format of
-           the input data. Default: ``'NCHW'``.
-        name (str, optional): For details, please refer to :ref:`api_guide_Name`. Generally, no setting is required. Default: ``'None'``.
+           the input data when: 1. mode is any of ``'reflect'``, ``'replicate'`` or ``'circular'``; or 2. the input ``'pad'`` is a tensor;
+           or 3. the length of ``'pad'`` is ``2*(x.ndim - 2)``. Default: ``'NCHW'``.
+        pad_from_left_axis (bool, optional): The parameter is only valid when mode is ``'constant'`` and the input ``'pad'`` is
+           length of ``'pad'`` is ``2*x.ndim``, the order of padding can be customized. If True, the padding will be started from
+           the first axis of ``'x'``; if False, it will be started from the last axis of ``'x'``. Default: True.
+        name (str|None, optional): For details, please refer to :ref:`api_guide_Name`. Generally, no setting is required. Default: ``'None'``.
 
     Returns:
         Tensor, a Tensor padded according to pad and mode and data type is same as input.
@@ -1735,43 +1752,71 @@ def pad(
                 pad = [0, 0, 0, 0, 0, 0, 1, 1, 0, 0],
                 mode = 'constant'
                 value = 0
+                pad_from_left_axis = True
                 Out = [[[[[0., 0., 0.],
                           [1., 2., 3.],
                           [4., 5., 6.],
                           [0., 0., 0.]]]]]
+                Out.shape = [1, 1, 1, 4, 3]
 
             Case 1:
+                pad = [0, 0, 0, 0, 0, 0, 1, 1, 0, 0],
+                mode = 'constant'
+                value = 0
+                pad_from_left_axis = False
+                Out = [[[[[0., 0., 0.],
+                          [0., 0., 0.]]],
+                        [[[1., 2., 3.],
+                          [4., 5., 6.]]],
+                        [[[0., 0., 0.],
+                          [0., 0., 0.]]]]]
+                Out.shape = [1, 3, 1, 2, 3]
+
+            Case 3:
+                pad = [1, 0, 0, 1],
+                mode = 'constant'
+                value = 0
+                Out = [[[[[0., 1., 2., 3.],
+                          [0., 4., 5., 6.],
+                          [0., 0., 0., 0.]]]]]
+                Out.shape = [1, 1, 1, 3, 4]
+
+            Case 4:
                 pad = [2, 2, 1, 1, 0, 0],
                 mode = 'constant'
                 value = 0
                 Out = [[[[[0. 0. 0. 0. 0. 0. 0.]
                           [0. 0. 1. 2. 3. 0. 0.]
                           [0. 0. 4. 5. 6. 0. 0.]
                           [0. 0. 0. 0. 0. 0. 0.]]]]]
+                Out.shape = [1, 1, 1, 4, 7]
 
-            Case 2:
+            Case 5:
                 pad = [2, 2, 1, 1, 0, 0],
                 mode = 'reflect'
                 Out = [[[[[6. 5. 4. 5. 6. 5. 4.]
                           [3. 2. 1. 2. 3. 2. 1.]
                           [6. 5. 4. 5. 6. 5. 4.]
                           [3. 2. 1. 2. 3. 2. 1.]]]]]
+                Out.shape = [1, 1, 1, 4, 7]
 
-            Case 3:
+            Case 6:
                 pad = [2, 2, 1, 1, 0, 0],
                 mode = 'replicate'
                 Out = [[[[[1. 1. 1. 2. 3. 3. 3.]
                           [1. 1. 1. 2. 3. 3. 3.]
                           [4. 4. 4. 5. 6. 6. 6.]
                           [4. 4. 4. 5. 6. 6. 6.]]]]]
+                Out.shape = [1, 1, 1, 4, 7]
 
-            Case 4:
+            Case 7:
                 pad = [2, 2, 1, 1, 0, 0],
                 mode = 'circular'
                 Out = [[[[[5. 6. 4. 5. 6. 4. 5.]
                           [2. 3. 1. 2. 3. 1. 2.]
                           [5. 6. 4. 5. 6. 4. 5.]
                           [2. 3. 1. 2. 3. 1. 2.]]]]]
+                Out.shape = [1, 1, 1, 4, 7]
 
     Examples:
         .. code-block:: python
@@ -1805,6 +1850,35 @@ def pad(
                [3., 1., 2., 3., 1., 2.],
                [6., 4., 5., 6., 4., 5.],
                [3., 1., 2., 3., 1., 2.]]]])
+
+            >>> # example 4
+            >>> x_shape = (1, 1, 3)
+            >>> x = paddle.arange(paddle.prod(paddle.to_tensor(x_shape)), dtype="float32").reshape(x_shape) + 1
+            >>> y = F.pad(x, [1, 0, 0, 1, 0, 0], value=0, mode='constant', pad_from_left_axis=True)
+            >>> print(y)
+            Tensor(shape=[2, 2, 3], dtype=float32, place=Place(cpu), stop_gradient=True,
+            [[[0., 0., 0.],
+              [0., 0., 0.]],
+             [[1., 2., 3.],
+              [0., 0., 0.]]])
+
+            >>> # example 5
+            >>> x_shape = (1, 1, 3)
+            >>> x = paddle.arange(paddle.prod(paddle.to_tensor(x_shape)), dtype="float32").reshape(x_shape) + 1
+            >>> y = F.pad(x, [1, 0, 0, 1, 0, 0], value=0, mode='constant', pad_from_left_axis=False)
+            >>> print(y)
+            Tensor(shape=[1, 2, 4], dtype=float32, place=Place(cpu), stop_gradient=True,
+            [[[0., 1., 2., 3.],
+              [0., 0., 0., 0.]]])
+
+            >>> # example 6
+            >>> x_shape = (1, 1, 3)
+            >>> x = paddle.arange(paddle.prod(paddle.to_tensor(x_shape)), dtype="float32").reshape(x_shape) + 1
+            >>> y = F.pad(x, [1, 0, 0, 1], value=0, mode='constant')
+            >>> print(y)
+            Tensor(shape=[1, 2, 4], dtype=float32, place=Place(cpu), stop_gradient=True,
+            [[[0., 1., 2., 3.],
+              [0., 0., 0., 0.]]])
     """
     assert mode in [
         'reflect',
@@ -1824,11 +1898,26 @@ def pad(
     if (
         mode == "constant"
         and isinstance(pad, (list, tuple))
-        and len(pad) == x_dim * 2
+        and len(pad) != (x_dim - 2) * 2
     ):
         paddings = pad
         pad_value = value
 
+        padding_len = len(paddings)
+        # pad the length of paddings to 2*x_dim
+        if padding_len < 2 * x_dim:
+            pad_len_for_paddings = 2 * x_dim - padding_len
+            paddings = paddings + ([0] if isinstance(pad, list) else (0,)) * (
+                pad_len_for_paddings
+            )
+
+        # since the kernel pad from left axis, if we want to pad from right axis, we need to reverse the paddings
+        if not (len(pad) == x_dim * 2 and pad_from_left_axis):
+            paddings = [
+                paddings[i - 1] if i % 2 == 1 else paddings[i + 1]
+                for i in range(2 * x_dim - 1, -1, -1)
+            ]
+
         if in_dynamic_mode():
             out = _C_ops.pad(x, paddings, float(pad_value))
             return out

test/legacy_test/test_pad_op.py

@@ -315,6 +315,114 @@ def test_check_grad(self):
         )
 
 
+class TestPadOrder2N(unittest.TestCase):
+    def init_case(self):
+        self.shape = [2, 3]
+        self.paddings = [(0, 1), (1, 0)]
+        self.pad_value = 0.5
+
+    def test_order(self):
+        self.init_case()
+        x_np = np.random.random(self.shape).astype('float32')
+        paddings_np = self.paddings.copy()
+        x = paddle.to_tensor(x_np)
+        paddings = list(np.array(self.paddings).flatten())
+
+        # pad_from_left_axis
+        pad_from_left_axis = True
+        out_np = np.pad(
+            x_np, paddings_np, mode="constant", constant_values=self.pad_value
+        )
+        out = paddle.nn.functional.pad(
+            x,
+            paddings,
+            mode='constant',
+            pad_from_left_axis=pad_from_left_axis,
+        )
+        np.testing.assert_array_equal(out, out_np)
+
+        # pad_from_right_axis:
+        pad_from_left_axis = False
+        paddings_np.reverse()
+        out_np = np.pad(
+            x_np, paddings_np, mode="constant", constant_values=self.pad_value
+        )
+        out = paddle.nn.functional.pad(
+            x,
+            paddings,
+            mode='constant',
+            pad_from_left_axis=pad_from_left_axis,
+        )
+        np.testing.assert_array_equal(out, out_np)
+
+
+# test padding order for cases when length of padding is not 2(N-2) or 2N
+class TestPadOrder(unittest.TestCase):
+    def init_case(self):
+        self.shape = [2, 3]
+        self.paddings = [(0, 1)]
+        self.pad_value = 0.5
+
+    def test_order(self):
+        self.init_case()
+        x_np = np.random.random(self.shape).astype('float32')
+        paddings_np = self.paddings.copy()
+        paddings_np += [(0, 0)] * (len(self.shape) - len(paddings_np))
+
+        x = paddle.to_tensor(x_np)
+        paddings = list(np.array(self.paddings).flatten())
+
+        # pad from last axis by default
+        paddings_np.reverse()
+        out_np = np.pad(
+            x_np, paddings_np, mode="constant", constant_values=self.pad_value
+        )
+        out = paddle.nn.functional.pad(x, paddings, mode='constant')
+        np.testing.assert_array_equal(out, out_np)
+
+
+class TestPadOrder2N3D(TestPadOrder2N):
+    def init_case(self):
+        self.shape = [2, 3, 4]
+        self.paddings = [(0, 1), (2, 3), (2, 1)]
+        self.pad_value = 0.5
+
+
+class TestPadOrder2N4D(TestPadOrder2N):
+    def init_case(self):
+        self.shape = [2, 3, 4, 5]
+        self.paddings = [(0, 1), (2, 3), (2, 1), (1, 1)]
+        self.pad_value = 0.5
+
+
+class TestPadOrder2N5D(TestPadOrder2N):
+    def init_case(self):
+        self.shape = [1, 2, 3, 4, 5]
+        self.paddings = [(0, 1), (2, 3), (2, 1), (1, 1), (1, 0)]
+        self.pad_value = 0.5
+
+
+class TestPadOrder1(TestPadOrder):
+    def init_case(self):
+        self.shape = [2, 3, 4]
+        self.paddings = [(0, 1), (2, 3)]
+        self.pad_value = 0.5
+
+
+class TestPadOrder2(TestPadOrder):
+    def init_case(self):
+        self.shape = [2, 3, 4, 5]
+        self.paddings = [(0, 1), (2, 3), (2, 1)]
+        self.pad_value = 0.5
+
+
+class TestPadOrder3(TestPadOrder):
+    def init_case(self):
+        self.shape = [2, 3, 4, 5]
+        self.paddings = [(0, 1)]
+        self.pad_value = 0.5
+
+
 if __name__ == "__main__":
     # paddle.enable_static()
     unittest.main()