Add API reference

paddle/fluid/operators/activation_op.cc

@@ -444,7 +444,7 @@ class SwishOpMaker : public framework::OpProtoAndCheckerMaker {
     AddComment(R"DOC(
 Swish Activation Operator.
 
-$$out = \frac{x}{1 + e^{- \beta x}}$$
+$$out = \\frac{x}{1 + e^{- \beta x}}$$
 
 )DOC");
   }

paddle/fluid/operators/pool_op.cc

@@ -204,8 +204,6 @@ void Pool2dOpMaker::Make() {
   // TODO(dzhwinter): need to registered layout transform function
 
   AddComment(R"DOC(
-Pool2d Operator.
-
 The pooling2d operation calculates the output based on
 the input, pooling_type and ksize, strides, paddings parameters.
 Input(X) and output(Out) are in NCHW format, where N is batch size, C is the
@@ -215,19 +213,28 @@ These two elements represent height and width, respectively.
 The input(X) size and output(Out) size may be different.
 
 Example:
+
   Input:
+
        X shape: $(N, C, H_{in}, W_{in})$
+
   Output:
+
        Out shape: $(N, C, H_{out}, W_{out})$
+
   For ceil_mode = false:
        $$
-       H_{out} = \frac{(H_{in} - ksize[0] + 2 * paddings[0])}{strides[0]} + 1 \\
-       W_{out} = \frac{(W_{in} - ksize[1] + 2 * paddings[1])}{strides[1]} + 1
+       H_{out} = \\frac{(H_{in} - ksize[0] + 2 * paddings[0])}{strides[0]} + 1
+       $$
+       $$
+       W_{out} = \\frac{(W_{in} - ksize[1] + 2 * paddings[1])}{strides[1]} + 1
        $$
   For ceil_mode = true:
        $$
-       H_{out} = \frac{(H_{in} - ksize[0] + 2 * paddings[0] + strides[0] - 1)}{strides[0]} + 1 \\
-       W_{out} = \frac{(W_{in} - ksize[1] + 2 * paddings[1] + strides[1] - 1)}{strides[1]} + 1
+       H_{out} = \\frac{(H_{in} - ksize[0] + 2 * paddings[0] + strides[0] - 1)}{strides[0]} + 1
+       $$
+       $$
+       W_{out} = \\frac{(W_{in} - ksize[1] + 2 * paddings[1] + strides[1] - 1)}{strides[1]} + 1
        $$
 
 )DOC");

python/paddle/fluid/layers/control_flow.py

@@ -748,17 +748,25 @@ def max_sequence_len(rank_table):
 
 
 def lod_tensor_to_array(x, table):
-    """ Convert a LOD_TENSOR to an LOD_TENSOR_ARRAY.
+    """ 
+    Convert a LoDTensor to a LoDTensorArray.
+
+    This function split a LoDTesnor to a LoDTensorArray according to its LoD 
+    information. LoDTensorArray is an alias of C++ std::vector<LoDTensor> in 
+    PaddlePaddle. The generated LoDTensorArray of this function can be further read 
+    or written by `read_from_array()` and `write_to_array()` operators. However, 
+    this function is generally an internal component of PaddlePaddle `DynamicRNN`. 
+    Users should not use it directly.
 
     Args:
-        x (Variable|list): The LOD tensor to be converted to a LOD tensor array.
+        x (Variable|list): The LoDTensor to be converted to a LoDTensorArray.
         table (ParamAttr|list): The variable that stores the level of lod
                                 which is ordered by sequence length in
-                                descending order.
+                                descending order. It is generally generated 
+                                by `layers.lod_rank_table()` API.
 
     Returns:
-        Variable: The variable of type array that has been converted from a
-                  tensor.
+        Variable: The LoDTensorArray that has been converted from the input tensor.
 
     Examples:
         .. code-block:: python
@@ -1047,6 +1055,13 @@ def array_length(array):
 
 
 class ConditionalBlockGuard(BlockGuard):
+    """
+    ConditionalBlockGuard is derived from BlockGuard. It is dedicated for 
+    holding a ConditionalBlock, and helping users entering and exiting the 
+    ConditionalBlock via Python's 'with' keyword. However, ConditionalBlockGuard 
+    is generally an internal component of IfElse, users should not use it directly.
+    """
+
     def __init__(self, block):
         if not isinstance(block, ConditionalBlock):
             raise TypeError("block should be conditional block")
@@ -1591,26 +1606,26 @@ def reorder_lod_tensor_by_rank(x, rank_table):
 
 def is_empty(x, cond=None, **ignored):
     """
-    **Is Empty**
-
-    This layer returns the truth value of whether the variable is empty.
+    Test whether a Variable is empty.
 
     Args:
-        x(Variable): Operand of *is_empty*
-        cond(Variable|None): Optional output variable to store the result
-                             of *is_empty*
+        x (Variable): The Variable to be tested.
+        cond (Variable|None): Output parameter. Returns the test result 
+                              of given 'x'. Default: None
 
     Returns:
-        Variable: The tensor variable storing the output of *is_empty*.
+        Variable: A bool scalar. True if 'x' is an empty Variable.
 
     Raises:
         TypeError: If input cond is not a variable, or cond's dtype is
-                   not bool
+                   not bool.
 
     Examples:
         .. code-block:: python
 
-          less = fluid.layers.is_empty(x=input)
+          res = fluid.layers.is_empty(x=input)
+          # or:
+          fluid.layers.is_empty(x=input, cond=res)
     """
     helper = LayerHelper("is_empty", **locals())
     if cond is None:

python/paddle/fluid/layers/io.py

@@ -549,6 +549,41 @@ def shuffle(reader, buffer_size):
 
 
 def batch(reader, batch_size):
+    """
+    This layer is a reader decorator. It takes a reader and adds 
+    'batching' decoration on it. When reading with the result 
+    decorated reader, output data will be automatically organized 
+    to the form of batches.
+
+    Args:
+        reader(Variable): The reader to be decorated with 'batching'.
+        batch_size(int): The batch size.
+
+    Returns:
+        Variable: The reader which has been decorated with 'batching'.
+
+    Examples:
+        .. code-block:: python
+
+            raw_reader = fluid.layers.io.open_files(filenames=['./data1.recordio',
+                                                           './data2.recordio'],
+                                                    shapes=[(3,224,224), (1)],
+                                                    lod_levels=[0, 0],
+                                                    dtypes=['float32', 'int64'],
+                                                    thread_num=2,
+                                                    buffer_size=2)
+            batch_reader = fluid.layers.batch(reader=raw_reader, batch_size=5)
+
+            # If we read data with the raw_reader:
+            #     data = fluid.layers.read_file(raw_reader)
+            # We can only get data instance by instance.
+            # 
+            # However, if we read data with the batch_reader:
+            #     data = fluid.layers.read_file(batch_reader)
+            # Each 5 adjacent instances will be automatically combined together 
+            # to become a batch. So what we get('data') is a batch data instead 
+            # of an instance.
+    """
     return __create_unshared_decorated_reader__(
         'create_batch_reader', reader, {'batch_size': int(batch_size)})
 
@@ -571,7 +606,33 @@ def parallel(reader):
                                               {})
 
 
-def read_file(file_obj):
+def read_file(reader):
+    """
+    Execute the given reader and get data via it.
+
+    A reader is also a Variable. It can be a raw reader generated by 
+    `fluid.layers.open_files()` or a decorated one generated by 
+    `fluid.layers.double_buffer()` and so on.
+
+    Args:
+
+        reader(Variable): The reader to execute.
+
+    Returns:
+        Tuple[Variable]: Data read via the given reader.
+
+    Examples:
+        .. code-block:: python
+
+           data_file = fluid.layers.open_files(
+                filenames=['mnist.recordio'],
+                shapes=[(-1, 748), (-1, 1)],
+                lod_levels=[0, 0],
+                dtypes=["float32", "int64"])
+            data_file = fluid.layers.double_buffer(
+                fluid.layers.batch(data_file, batch_size=64))
+            input, label = fluid.layers.read_file(data_file)
+    """
     helper = LayerHelper('read_file')
     out = [
         helper.create_tmp_variable(

python/paddle/fluid/layers/learning_rate_scheduler.py

@@ -70,21 +70,40 @@ def noam_decay(d_model, warmup_steps):
 
 
 def exponential_decay(learning_rate, decay_steps, decay_rate, staircase=False):
-    """Applies exponential decay to the learning rate.
+    """
+    Applies exponential decay to the learning rate. 
+
+    When training a model, it is often recommended to lower the learning rate as the 
+    training progresses. By using this function, the learning rate will be decayed by 
+    'decay_rate' every 'decay_steps' steps.
+
+    >>> if staircase == True:
+    >>>     decayed_learning_rate = learning_rate * decay_rate ^ floor(global_step / decay_steps)
+    >>> else:
+    >>>     decayed_learning_rate = learning_rate * decay_rate ^ (global_step / decay_steps)
 
-    ```python
-    decayed_learning_rate = learning_rate *
-            decay_rate ^ (global_step / decay_steps)
-    ```
     Args:
-        learning_rate: A scalar float32 value or a Variable. This
-          will be the initial learning rate during training
-        decay_steps: A Python `int32` number.
-        decay_rate: A Python `float` number.
-        staircase: Boolean. If set true, decay the learning rate every decay_steps.
+        learning_rate(Variable|float): The initial learning rate.
+        decay_steps(int): See the decay computation above.
+        decay_rate(float): The decay rate. See the decay computation above.
+        staircase(Boolean): If True, decay the learning rate at discrete intervals.
+                            Default: False
 
     Returns:
-        The decayed learning rate
+        Variable: The decayed learning rate
+
+    Examples:
+        .. code-block:: python
+
+          base_lr = 0.1
+          sgd_optimizer = fluid.optimizer.SGD(
+                learning_rate=fluid.layers.exponential_decay(
+                    learning_rate=base_lr,
+                    decay_steps=10000,
+                    decay_rate=0.5,
+                    staircase=True))
+          sgd_optimizer.minimize(avg_cost)
+
     """
     global_step = _decay_step_counter()
 
@@ -128,22 +147,39 @@ def natural_exp_decay(learning_rate, decay_steps, decay_rate, staircase=False):
 
 
 def inverse_time_decay(learning_rate, decay_steps, decay_rate, staircase=False):
-    """Applies inverse time decay to the initial learning rate.
+    """
+    Applies inverse time decay to the initial learning rate.
+
+    When training a model, it is often recommended to lower the learning rate as the 
+    training progresses. By using this function, an inverse decay function will be 
+    applied to the initial learning rate.
 
-    >>> if staircase:
+    >>> if staircase == True:
     >>>     decayed_learning_rate = learning_rate / (1 + decay_rate * floor(global_step / decay_step))
     >>> else:
     >>>     decayed_learning_rate = learning_rate / (1 + decay_rate * global_step / decay_step)
 
     Args:
-        learning_rate: A scalar float32 value or a Variable. This
-          will be the initial learning rate during training.
-        decay_steps: A Python `int32` number.
-        decay_rate: A Python `float` number.
-        staircase: Boolean. If set true, decay the learning rate every decay_steps.
+        learning_rate(Variable|float): The initial learning rate.
+        decay_steps(int): See the decay computation above.
+        decay_rate(float): The decay rate. See the decay computation above.
+        staircase(Boolean): If True, decay the learning rate at discrete intervals.
+                            Default: False
 
     Returns:
-        The decayed learning rate
+        Variable: The decayed learning rate
+
+    Examples:
+        .. code-block:: python
+
+          base_lr = 0.1
+          sgd_optimizer = fluid.optimizer.SGD(
+                learning_rate=fluid.layers.inverse_time_decay(
+                    learning_rate=base_lr,
+                    decay_steps=10000,
+                    decay_rate=0.5,
+                    staircase=True))
+          sgd_optimizer.minimize(avg_cost)
     """
     global_step = _decay_step_counter()