Enhance pad_constant_like_op (#12999)

* enhance pad_constant_like_op

* add API

* add API

paddle/fluid/API.spec

@@ -147,6 +147,7 @@ paddle.fluid.layers.reshape ArgSpec(args=['x', 'shape', 'actual_shape', 'act', '
 paddle.fluid.layers.lod_reset ArgSpec(args=['x', 'y', 'target_lod'], varargs=None, keywords=None, defaults=(None, None))
 paddle.fluid.layers.lrn ArgSpec(args=['input', 'n', 'k', 'alpha', 'beta', 'name'], varargs=None, keywords=None, defaults=(5, 1.0, 0.0001, 0.75, None))
 paddle.fluid.layers.pad ArgSpec(args=['x', 'paddings', 'pad_value', 'name'], varargs=None, keywords=None, defaults=(0.0, None))
+paddle.fluid.layers.pad_constant_like ArgSpec(args=['x', 'y', 'pad_value', 'name'], varargs=None, keywords=None, defaults=(0.0, None))
 paddle.fluid.layers.label_smooth ArgSpec(args=['label', 'prior_dist', 'epsilon', 'dtype', 'name'], varargs=None, keywords=None, defaults=(None, 0.1, 'float32', None))
 paddle.fluid.layers.roi_pool ArgSpec(args=['input', 'rois', 'pooled_height', 'pooled_width', 'spatial_scale'], varargs=None, keywords=None, defaults=(1, 1, 1.0))
 paddle.fluid.layers.dice_loss ArgSpec(args=['input', 'label', 'epsilon'], varargs=None, keywords=None, defaults=(1e-05,))

paddle/fluid/operators/pad_constant_like_op.cc

@@ -43,6 +43,14 @@ class PadConstantLikeOp : public framework::OperatorWithKernel {
     ctx->SetOutputDim("Out", x_dim);
     ctx->ShareLoD("X", /*->*/ "Out");
   }
+
+ protected:
+  framework::OpKernelType GetExpectedKernelType(
+      const framework::ExecutionContext &ctx) const override {
+    return framework::OpKernelType(
+        framework::ToDataType(ctx.Input<Tensor>("Y")->type()),
+        ctx.device_context());
+  }
 };
 
 class PadConstantLikeOpMaker : public framework::OpProtoAndCheckerMaker {
@@ -159,6 +167,14 @@ class PadConstantLikeOpGrad : public framework::OperatorWithKernel {
       }
     }
   }
+
+ protected:
+  framework::OpKernelType GetExpectedKernelType(
+      const framework::ExecutionContext &ctx) const override {
+    return framework::OpKernelType(
+        framework::ToDataType(ctx.Input<Tensor>("Y")->type()),
+        ctx.device_context());
+  }
 };
 
 class PadConstantLikeOpGradMaker : public framework::SingleGradOpDescMaker {

python/paddle/fluid/layers/nn.py

@@ -88,6 +88,7 @@ __all__ = [
     'lod_reset',
     'lrn',
     'pad',
+    'pad_constant_like',
     'label_smooth',
     'roi_pool',
     'dice_loss',
@@ -4755,6 +4756,86 @@ def pad(x, paddings, pad_value=0., name=None):
     return out
 
 
+def pad_constant_like(x, y, pad_value=0., name=None):
+    """
+    Pad input(Y) with :attr:`pad_value`, the number of values padded to
+    the edges of each axis is specified by the difference of the shape
+    of X and Y. ((0, shape_x_0 - shape_y_0), ... (0, shape_x_n - shape_y_n))
+    unique pad widths for each axis. The input should be a k-D
+    tensor(k > 0 and k < 7).
+
+    See below for an example.
+
+    .. code-block:: text
+
+        Given:
+            X = [[[[ 0,  1,  2],
+                   [ 3,  4,  5]],
+                  [[ 6,  7,  8],
+                   [ 9, 10, 11]],
+                  [[12, 13, 14],
+                   [15, 16, 17]]],
+                 [[[18, 19, 20],
+                   [21, 22, 23]],
+                  [[24, 25, 26],
+                   [27, 28, 29]],
+                  [[30, 31, 32],
+                   [33, 34, 35]]]]
+            X.shape = (2, 3, 2, 3)
+
+            Y = [[[[35, 36, 37]],
+                  [[38, 39, 40]],
+                  [[41, 42, 43]]]]
+            Y.shape = (1, 3, 1, 3)
+
+    And
+        pad_value = -1,
+
+    Return:
+        Out = [[[[35, 36, 37],
+                  [-1, -1, -1]],
+                [[38, 39, 40],
+                  [-1, -1, -1]],
+                 [[41, 42, 43],
+                  [-1, -1, -1]]],
+                [[[-1, -1, -1],
+                  [-1, -1, -1]],
+                 [[-1, -1, -1],
+                  [-1, -1, -1]],
+                 [[-1, -1, -1],
+                  [-1, -1, -1]]]]
+        Out.shape = (2, 3, 2, 3)
+
+    Args:
+        x (Variable): The input tensor variable.
+        y (Variable): The input tensor variable.
+        pad_value (float): The constant value used to pad.
+        name(str|None): A name for this layer(optional). If set None, the layer
+                        will be named automatically.
+
+    Returns:
+        Variable: The padded tensor variable.
+
+    Examples:
+        .. code-block:: python
+
+            # x is a rank 4 tensor variable, x.shape = (2, 3, 2, 3)
+            # y is a rank 4 tensor variable, y.shape = (1, 3, 1, 3)
+            out = fluid.layers.pad_constant_like(x=x, y=y, pad_value=0.)
+            # out is a rank 4 tensor variable, and out.shape = [2, 3 ,2 , 3]
+    """
+    helper = LayerHelper('pad_constant_like', input=x, **locals())
+    dtype = helper.input_dtype()
+    out = helper.create_tmp_variable(dtype)
+    helper.append_op(
+        type='pad_constant_like',
+        inputs={'X': x,
+                'Y': y},
+        outputs={'Out': out},
+        attrs={'pad_value': float(pad_value)})
+    return out
+
+
 def label_smooth(label,
                  prior_dist=None,
                  epsilon=0.1,