add SELU to Tensor (tinygrad#7993)

* add selu

* more clean ups

docs/tensor/elementwise.md

@@ -37,6 +37,7 @@ Elementwise ops operate on a per element basis. They don't change the shape of t
 ::: tinygrad.Tensor.hardsigmoid
 ::: tinygrad.Tensor.elu
 ::: tinygrad.Tensor.celu
+::: tinygrad.Tensor.selu
 ::: tinygrad.Tensor.swish
 ::: tinygrad.Tensor.silu
 ::: tinygrad.Tensor.relu6

extra/onnx_ops.py

@@ -8,7 +8,7 @@
 
 tensor_methods = {"Neg", "Reciprocal", "Pow", "Sqrt", "Sign", "Abs", "Exp", "Log", "Mish", "Sin", "Cos", "Tan", "Asin", "Acos", "Atan","Relu",
                   "Sigmoid", "MatMul", "Floor", "Ceil", "Softplus", "HardSwish", "Where", "Mul", "Sinh", "Cosh", "Tanh", "Softsign",
-                  "Asinh", "Acosh", "Atanh",  "Elu", "Celu", "Xor", "Round", "Erf"}
+                  "Asinh", "Acosh", "Atanh",  "Elu", "Celu", "Selu", "Xor", "Round", "Erf"}
 
 # **************** Free Ops ****************
 
@@ -44,7 +44,6 @@ def Constant(value:Optional[Tensor]=None, value_float=None, value_floats=None, v
 
 def HardSigmoid(x: Tensor, alpha=0.2, beta=0.5): return (alpha*x + beta).clip(0, 1)
 def Gelu(x:Tensor, approximate=None): return x.gelu() if approximate == "tanh" else 0.5 * x * (1 + (x/math.sqrt(2)).erf())
-def Selu(X: Tensor, alpha=1.67326319217681884765625, gamma=1.05070102214813232421875): return gamma * (X.relu() - (-alpha*X.exp()+alpha).relu())
 def PRelu(X:Tensor, slope:Tensor):
   slope = slope[0] if slope.shape[-1] != X.shape[-1] else slope # HACK OnnxBackendPyTorchConvertedModelTest HAS WEIRD SLOPE WHERE IT'S [0.25, 0.25, 0.25] FOR ANY X.SHAPE
   return (X > 0).where(X, X * slope)

test/test_ops.py

@@ -697,6 +697,9 @@ def test_celu(self):
     for val in range(1, 5):
       helper_test_op([(45,65)], lambda x: torch.nn.functional.celu(x,val), lambda x: x.celu(val))
       helper_test_op([()], lambda x: torch.nn.functional.celu(x,val), lambda x: x.celu(val))
+  def test_selu(self):
+    helper_test_op([(45,65)], torch.nn.functional.selu, Tensor.selu)
+    helper_test_op([()], torch.nn.functional.selu, Tensor.selu)
 
   def test_abs(self):
     helper_test_op([(45,65)], torch.abs, Tensor.abs)

tinygrad/tensor.py

@@ -2688,6 +2688,19 @@ def celu(self, alpha=1.0):
     """
     return self.maximum(0) + (alpha * ((self / alpha).exp() - 1)).minimum(0)
 
+  def selu(self, alpha=1.67326, gamma=1.0507):
+    """
+    Applies the Scaled Exponential Linear Unit (SELU) function element-wise.
+
+    - Described: https://paperswithcode.com/method/selu
+    - Paper: https://arxiv.org/abs/1706.02515v5
+
+    ```python exec="true" source="above" session="tensor" result="python"
+    print(Tensor([-3., -2., -1., 0., 1., 2., 3.]).selu().numpy())
+    ```
+    """
+    return gamma * (self >= 0).detach().where(self, alpha * (self.exp() - 1))
+
   def swish(self):
     """
     See `.silu()`