Add the constraint for the scale of SELU/selu (#26686)

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

@@ -130,6 +130,11 @@ class TestSeluAPI(unittest.TestCase):
             # The input dtype must be float16, float32, float64.
             x_int32 = paddle.data(name='x_int32', shape=[12, 10], dtype='int32')
             self.assertRaises(TypeError, F.selu, x_int32)
+            # The scale must be greater than 1.0
+            x_fp32 = paddle.data(name='x_fp32', shape=[12, 10], dtype='float32')
+            self.assertRaises(ValueError, F.selu, x_fp32, -1.0)
+            # The alpha must be no less than 0
+            self.assertRaises(ValueError, F.selu, x_fp32, 1.6, -1.0)
             # support the input dtype is float16
             x_fp16 = paddle.data(name='x_fp16', shape=[12, 10], dtype='float16')
             F.selu(x_fp16)

python/paddle/nn/functional/activation.py

@@ -652,8 +652,8 @@ def selu(x,
 
     Parameters:
         x (Tensor): The input Tensor with data type float32, float64.
-        scale (float, optional): The value of scale for selu. Default is 1.0507009873554804934193349852946
-        alpha (float, optional): The value of alpha for selu. Default is 1.6732632423543772848170429916717
+        scale (float, optional): The value of scale(must be greater than 1.0) for selu. Default is 1.0507009873554804934193349852946
+        alpha (float, optional): The value of alpha(must be no less than zero) for selu. Default is 1.6732632423543772848170429916717
         name (str, optional): Name for the operation (optional, default is None).
             For more information, please refer to :ref:`api_guide_Name`.
 
@@ -672,6 +672,14 @@ def selu(x,
             x = paddle.to_tensor(np.array([[0.0, 1.0],[2.0, 3.0]]))
             out = F.selu(x) # [[0, 1.050701],[2.101402, 3.152103]]
     """
+    if scale <= 1.0:
+        raise ValueError(
+            "The scale must be greater than 1.0. Received: {}.".format(scale))
+
+    if alpha < 0:
+        raise ValueError(
+            "The alpha must be no less than zero. Received: {}.".format(alpha))
+
     if in_dygraph_mode():
         return core.ops.selu(x, 'scale', scale, 'alpha', alpha)
 

python/paddle/nn/layer/activation.py

@@ -559,8 +559,8 @@ class SELU(layers.Layer):
                  \\end{cases}
 
     Parameters:
-        scale (float, optional): The value of scale for SELU. Default is 1.0507009873554804934193349852946
-        alpha (float, optional): The value of alpha for SELU. Default is 1.6732632423543772848170429916717
+        scale (float, optional): The value of scale(must be greater than 1.0) for SELU. Default is 1.0507009873554804934193349852946
+        alpha (float, optional): The value of alpha(must be no less than zero) for SELU. Default is 1.6732632423543772848170429916717
         name (str, optional): Name for the operation (optional, default is None).
             For more information, please refer to :ref:`api_guide_Name`.