Added some docstrings ops/nn.py (#677)

* Small typo

* Added some docstrings

* Remove extra lines

* Unindent examples // use floats in example section

keras_core/activations/activations.py

@@ -429,7 +429,7 @@ def log_softmax(x, axis=-1):
     is applied along.
 
     Args:
-        x : Input tensor.
+        x: Input tensor.
         axis: Integer, axis along which the softmax is applied.
     """
     return ops.log_softmax(x, axis=axis)

keras_core/ops/nn.py

@@ -22,6 +22,24 @@ def compute_output_spec(self, x):
 
 @keras_core_export(["keras_core.ops.relu", "keras_core.ops.nn.relu"])
 def relu(x):
+    """Rectified linear unit activation function.
+
+    It is defined as `f(x) = max(0, x)`.
+
+    Args:
+        x: Input tensor.
+
+    Returns:
+        A tensor with the same shape as `x`.
+
+    Example:
+
+    >>> x = np.array([-1., 0., 1.])
+    >>> x_relu = keras_core.ops.relu(x)
+    >>> print(x_relu)
+    array([0., 0., 1.], shape=(3,), dtype=float64)
+
+    """
     if any_symbolic_tensors((x,)):
         return Relu().symbolic_call(x)
     return backend.nn.relu(x)
@@ -37,6 +55,24 @@ def compute_output_spec(self, x):
 
 @keras_core_export(["keras_core.ops.relu6", "keras_core.ops.nn.relu6"])
 def relu6(x):
+    """Rectified linear unit activation function with upper bound of 6.
+
+    It is defined as `f(x) = np.clip(x, 0, 6)`.
+
+    Args:
+        x: Input tensor.
+
+    Returns:
+        A tensor with the same shape as `x`.
+
+    Example:
+
+    >>> x = np.array([-1., 0., 1., 6., 7.])
+    >>> x_relu6 = keras_core.ops.relu6(x)
+    >>> print(x_relu6)
+    array([0., 0., 1., 6., 6.], shape=(5,), dtype=float64)
+
+    """
     if any_symbolic_tensors((x,)):
         return Relu6().symbolic_call(x)
     return backend.nn.relu6(x)
@@ -52,6 +88,24 @@ def compute_output_spec(self, x):
 
 @keras_core_export(["keras_core.ops.sigmoid", "keras_core.ops.nn.sigmoid"])
 def sigmoid(x):
+    """Sigmoid activation function.
+
+    It is defined as `f(x) = 1 / (1 + exp(-x))`.
+
+    Args:
+        x: Input tensor.
+
+    Returns:
+        A tensor with the same shape as `x`.
+
+    Example:
+
+    >>> x = np.array([-1., 0., 1.])
+    >>> x_sigmoid = keras_core.ops.sigmoid(x)
+    >>> print(x_sigmoid)
+    array([0.26894143, 0.5, 0.7310586 ], dtype=float64)
+
+    """
     if any_symbolic_tensors((x,)):
         return Sigmoid().symbolic_call(x)
     return backend.nn.sigmoid(x)
@@ -67,6 +121,25 @@ def compute_output_spec(self, x):
 
 @keras_core_export(["keras_core.ops.softplus", "keras_core.ops.nn.softplus"])
 def softplus(x):
+    """Softplus activation function.
+
+    It is defined as `f(x) = log(exp(x) + 1)`, where `log` is the natural
+    logarithm and `exp` is the exponential function.
+
+    Args:
+        x: Input tensor.
+
+    Returns:
+        A tensor with the same shape as `x`.
+
+    Example:
+
+    >>> x = np.array([-1., 0., 1.])
+    >>> x_softplus = keras_core.ops.softplus(x)
+    >>> print(x_softplus)
+    array([0.31326166, 0.6931472 , 1.3132616 ], shape=(3,), dtype=float64)
+
+    """
     if any_symbolic_tensors((x,)):
         return Softplus().symbolic_call(x)
     return backend.nn.softplus(x)
@@ -82,6 +155,24 @@ def compute_output_spec(self, x):
 
 @keras_core_export(["keras_core.ops.softsign", "keras_core.ops.nn.softsign"])
 def softsign(x):
+    """Softsign activation function.
+
+    It is defined as `f(x) = x / (abs(x) + 1)`.
+
+    Args:
+        x: Input tensor.
+
+    Returns:
+        A tensor with the same shape as `x`.
+
+    Example:
+
+    >>> x = np.array([-1., 0., 1.])
+    >>> x_softsign = keras_core.ops.softsign(x)
+    >>> print(x_softsign)
+    array([-0.5, 0., 0.5], shape=(3,), dtype=float64)
+
+    """
     if any_symbolic_tensors((x,)):
         return Softsign().symbolic_call(x)
     return backend.nn.softsign(x)
@@ -97,6 +188,24 @@ def compute_output_spec(self, x):
 
 @keras_core_export(["keras_core.ops.silu", "keras_core.ops.nn.silu"])
 def silu(x):
+    """Sigmoid-weighted linear unit activation function.
+
+    It is defined as `f(x) = x * sigmoid(x)`.
+
+    Args:
+        x: Input tensor.
+
+    Returns:
+        A tensor with the same shape as `x`.
+
+    Example:
+
+    >>> x = np.array([-1., 0., 1.])
+    >>> x_silu = keras_core.ops.silu(x)
+    >>> print(x_silu)
+    array([-0.26894143, 0., 0.7310586], shape=(3,), dtype=float64)
+
+    """
     if any_symbolic_tensors((x,)):
         return Silu().symbolic_call(x)
     return backend.nn.silu(x)
@@ -132,6 +241,24 @@ def compute_output_spec(self, x):
     ]
 )
 def log_sigmoid(x):
+    """Logarithm of the sigmoid activation function.
+
+    It is defined as `f(x) = log(1 / (1 + exp(-x)))`.
+
+    Args:
+        x: Input tensor.
+
+    Returns:
+        A tensor with the same shape as `x`.
+
+    Example:
+
+    >>> x = np.array([-1., 0., 1.])
+    >>> x_log_sigmoid = keras_core.ops.log_sigmoid(x)
+    >>> print(x_log_sigmoid)
+    array([-1.3132616, -0.6931472, -0.3132616], shape=(3,), dtype=float64)
+
+    """
     if any_symbolic_tensors((x,)):
         return LogSigmoid().symbolic_call(x)
     return backend.nn.log_sigmoid(x)
@@ -153,6 +280,28 @@ def compute_output_spec(self, x):
     ["keras_core.ops.leaky_relu", "keras_core.ops.nn.leaky_relu"]
 )
 def leaky_relu(x, negative_slope=0.2):
+    """Leaky version of a Rectified Linear Unit.
+
+    It allows a small gradient when the unit is not active, it is defined as:
+
+    `f(x) = alpha * x for x < 0` or `f(x) = x for x >= 0`.
+
+    Args:
+        x: Input tensor.
+        negative_slope: Slope of the activation function at x < 0.
+            Defaults to `0.2`.
+
+    Returns:
+        A tensor with the same shape as `x`.
+
+    Example:
+
+    >>> x = np.array([-1., 0., 1.])
+    >>> x_leaky_relu = keras_core.ops.leaky_relu(x)
+    >>> print(x_leaky_relu)
+    array([-0.2,  0. ,  1. ], shape=(3,), dtype=float64)
+
+    """
     if any_symbolic_tensors((x,)):
         return LeakyRelu(negative_slope).symbolic_call(x)
     return backend.nn.leaky_relu(x, negative_slope=negative_slope)
@@ -173,6 +322,26 @@ def compute_output_spec(self, x):
     ]
 )
 def hard_sigmoid(x):
+    """Hard sigmoid activation function.
+
+    It is defined as:
+
+    `0 if x < -2.5`, `1 if x > 2.5`, `(0.2 * x) + 0.5 if -2.5 <= x <= 2.5`.
+
+    Args:
+        x: Input tensor.
+
+    Returns:
+        A tensor with the same shape as `x`.
+
+    Example:
+
+    >>> x = np.array([-1., 0., 1.])
+    >>> x_hard_sigmoid = keras_core.ops.hard_sigmoid(x)
+    >>> print(x_hard_sigmoid)
+    array([0.3, 0.5, 0.7], shape=(3,), dtype=float64)
+
+    """
     if any_symbolic_tensors((x,)):
         return HardSigmoid().symbolic_call(x)
     return backend.nn.hard_sigmoid(x)
@@ -192,6 +361,27 @@ def compute_output_spec(self, x):
 
 @keras_core_export(["keras_core.ops.elu", "keras_core.ops.nn.elu"])
 def elu(x, alpha=1.0):
+    """Exponential Linear Unit.
+
+    It is defined as:
+
+    `f(x) =  alpha * (exp(x) - 1.) for x < 0`, `f(x) = x for x >= 0`.
+
+    Args:
+        x: Input tensor.
+        alpha: A scalar, slope of positive section. Defaults to `1.0`.
+
+    Returns:
+        A tensor with the same shape as `x`.
+
+    Example:
+
+    >>> x = np.array([-1., 0., 1.])
+    >>> x_elu = keras_core.ops.elu(x)
+    >>> print(x_elu)
+    array([-0.63212055, 0., 1.], shape=(3,), dtype=float64)
+
+    """
     if any_symbolic_tensors((x,)):
         return Elu(alpha).symbolic_call(x)
     return backend.nn.elu(x, alpha=alpha)
@@ -207,6 +397,27 @@ def compute_output_spec(self, x):
 
 @keras_core_export(["keras_core.ops.selu", "keras_core.ops.nn.selu"])
 def selu(x):
+    """Scaled Exponential Linear Unit (SELU).
+
+    It is defined as:
+
+    `f(x) =  scale * alpha * (exp(x) - 1.) for x < 0`,
+    `f(x) = scale * x for x >= 0`.
+
+    Args:
+        x: Input tensor.
+
+    Returns:
+        A tensor with the same shape as `x`.
+
+    Example:
+
+    >>> x = np.array([-1., 0., 1.])
+    >>> x_selu = keras_core.ops.selu(x)
+    >>> print(x_selu)
+    array([-1.11133055, 0., 1.05070098], shape=(3,), dtype=float64)
+
+    """
     if any_symbolic_tensors((x,)):
         return Selu().symbolic_call(x)
     return backend.nn.selu(x)