Polish api Program/CompiledProgram/ParallelEnv doc & code example (#27656)

* polish Program api doc & example

* polish CompiledProgram api doc & example

* polish ParallelEnv api doc & examples

* polish details, test=document_fix

* polish program doc details, test=document_fix

* polish details, test=document_fix

* fix note format error, test=document_fix

* add lost example, test=document_fix

* fix lost example, test=document_fix

python/paddle/fluid/compiler.py

@@ -93,16 +93,16 @@ class CompiledProgram(object):
     for example, the operators' fusion in the computation graph, memory
     optimization during the execution of the computation graph, etc.
     For more information about build_strategy, please refer to
-    :code:`fluid.BuildStrategy`.
+    :code:`paddle.static.BuildStrategy`.
 
     Args:
-        program_or_graph (Graph|Program): This parameter is the Program or Graph
+        program_or_graph (Graph|Program): This argument is the Program or Graph
             being executed.
-        build_strategy(BuildStrategy): This parameter is used to compile the
+        build_strategy(BuildStrategy): This argument is used to compile the
             program or graph with the specified options, such as operators' fusion
             in the computational graph and memory optimization during the execution
             of the computational graph. For more information about build_strategy,
-            please refer to :code:`fluid.BuildStrategy`. The default is None.
+            please refer to :code:`paddle.static.BuildStrategy`. The default is None.
 
     Returns:
         CompiledProgram
@@ -110,20 +110,23 @@ class CompiledProgram(object):
     Example:
         .. code-block:: python
 
-          import paddle.fluid as fluid
             import numpy
+            import paddle
+            import paddle.static as static
+
+            paddle.enable_static()
 
-          place = fluid.CUDAPlace(0) # fluid.CPUPlace()
-          exe = fluid.Executor(place)
+            place = paddle.CUDAPlace(0) # paddle.CPUPlace()
+            exe = static.Executor(place)
 
-          data = fluid.data(name='X', shape=[None, 1], dtype='float32')
-          hidden = fluid.layers.fc(input=data, size=10)
-          loss = fluid.layers.mean(hidden)
-          fluid.optimizer.SGD(learning_rate=0.01).minimize(loss)
+            data = static.data(name='X', shape=[None, 1], dtype='float32')
+            hidden = static.nn.fc(input=data, size=10)
+            loss = paddle.mean(hidden)
+            paddle.optimizer.SGD(learning_rate=0.01).minimize(loss)
 
-          exe.run(fluid.default_startup_program())
-          compiled_prog = fluid.CompiledProgram(
-                   fluid.default_main_program())
+            exe.run(static.default_startup_program())
+            compiled_prog = static.CompiledProgram(
+                static.default_main_program())
 
             x = numpy.random.random(size=(10, 1)).astype('float32')
             loss_data, = exe.run(compiled_prog,
@@ -169,13 +172,16 @@ class CompiledProgram(object):
         exec_strategy to set some optimizations that can be applied during the construction
         and computation of the Graph, such as reducing the number of AllReduce operations,
         specifying the size of the thread pool used in the computation Graph running the model,
-        and so on. **Note: If build_strategy is specified when building CompiledProgram and calling
+        and so on. 
+        
+        .. note::
+            If build_strategy is specified when building CompiledProgram and calling 
             with_data_parallel, build_strategy in CompiledProgram will be overwritten, therefore, 
             if it is data parallel training, it is recommended to set build_strategy when calling 
-        with_data_parallel interface.**
+            with_data_parallel interface.
 
         Args:
-            loss_name (str): This parameter is the name of the loss variable of the model.
+            loss_name (str): This parameter is the name of the loss Tensor of the model.
                 **Note: If it is model training, you must set loss_name, otherwise the
                 result may be problematic**. The default is None.
             build_strategy(BuildStrategy): This parameter is used to compile the
@@ -192,7 +198,7 @@ class CompiledProgram(object):
                 specified by share_vars_from. This parameter needs to be set when model testing
                 is required during model training, and the data parallel mode is used for
                 training and testing. Since CompiledProgram will only distribute parameter
-                variables to other devices when it is first executed, the CompiledProgram
+                Tensors to other devices when it is first executed, the CompiledProgram
                 specified by share_vars_from must be run before the current CompiledProgram.
                 The default is None.
             places(list(CUDAPlace)|list(CPUPlace)|None): This parameter specifies the device
@@ -214,16 +220,19 @@ class CompiledProgram(object):
         Example:
             .. code-block:: python
 
-              import paddle.fluid as fluid
                 import numpy
                 import os
+                import paddle
+                import paddle.static as static
+
+                paddle.enable_static()
 
                 use_cuda = True
-              place = fluid.CUDAPlace(0) if use_cuda else fluid.CPUPlace()
-              parallel_places = [fluid.CUDAPlace(0), fluid.CUDAPlace(1)] if use_cuda else [fluid.CPUPlace()] * 2
+                place = paddle.CUDAPlace(0) if use_cuda else paddle.CPUPlace()
+                parallel_places = [paddle.CUDAPlace(0), paddle.CUDAPlace(1)] if use_cuda else [paddle.CPUPlace()] * 2
 
                 # NOTE: If you use CPU to run the program, you need
-              # to specify the CPU_NUM, otherwise, fluid will use
+                # to specify the CPU_NUM, otherwise, paddle will use
                 # all the number of the logic core as the CPU_NUM,
                 # in that case, the batch size of the input should be
                 # greater than CPU_NUM, if not, the process will be
@@ -231,23 +240,23 @@ class CompiledProgram(object):
                 if not use_cuda:
                     os.environ['CPU_NUM'] = str(2)
 
-              exe = fluid.Executor(place)
+                exe = static.Executor(place)
 
-              data = fluid.data(name='X', shape=[None, 1], dtype='float32')
-              hidden = fluid.layers.fc(input=data, size=10)
-              loss = fluid.layers.mean(hidden)
+                data = static.data(name='X', shape=[None, 1], dtype='float32')
+                hidden = static.nn.fc(input=data, size=10)
+                loss = paddle.mean(hidden)
 
-              test_program = fluid.default_main_program().clone(for_test=True)
-              fluid.optimizer.SGD(learning_rate=0.01).minimize(loss)
+                test_program = static.default_main_program().clone(for_test=True)
+                paddle.optimizer.SGD(learning_rate=0.01).minimize(loss)
 
-              exe.run(fluid.default_startup_program())
-              compiled_train_prog = fluid.CompiledProgram(
-                  fluid.default_main_program()).with_data_parallel(
+                exe.run(static.default_startup_program())
+                compiled_train_prog = static.CompiledProgram(
+                    static.default_main_program()).with_data_parallel(
                             loss_name=loss.name, places=parallel_places)
                 # NOTE: if not set share_vars_from=compiled_train_prog,
                 # the parameters used in test process are different with 
                 # the parameters used by train process
-              compiled_test_prog = fluid.CompiledProgram(
+                compiled_test_prog = static.CompiledProgram(
                     test_program).with_data_parallel(
                             share_vars_from=compiled_train_prog,
                             places=parallel_places)

python/paddle/fluid/dygraph/parallel.py

@@ -61,60 +61,44 @@ def prepare_context(strategy=None):
 
 class ParallelEnv(object):
     """
-    **Notes**:
-        **The old class name was Env and will be deprecated. Please use new class name ParallelEnv.**
+    .. note::
+        This API is not recommended, if you need to get rank and world_size, 
+        it is recommended to use ``paddle.distributed.get_rank()`` and 
+        ``paddle.distributed.get_world_size()`` .
 
     This class is used to obtain the environment variables required for 
-    the parallel execution of dynamic graph model.
+    the parallel execution of ``paddle.nn.Layer`` in dynamic mode.
 
-    The dynamic graph parallel mode needs to be started using paddle.distributed.launch.
-    By default, the related environment variable is automatically configured by this module.
-
-    This class is generally used in with `fluid.dygraph.DataParallel` to configure dynamic graph models
-    to run in parallel.
+    The parallel execution in dynamic mode needs to be started using ``paddle.distributed.launch`` 
+    or ``paddle.distributed.spawn`` .
 
     Examples:
       .. code-block:: python
 
-        # This example needs to run with paddle.distributed.launch, The usage is:
-        #   python -m paddle.distributed.launch --selected_gpus=0,1 example.py
-        # And the content of `example.py` is the code of following example.
-
-        import numpy as np
-        import paddle.fluid as fluid
-        import paddle.fluid.dygraph as dygraph
-        from paddle.fluid.optimizer import AdamOptimizer
-        from paddle.fluid.dygraph.nn import Linear
-        from paddle.fluid.dygraph.base import to_variable
-
-        place = fluid.CUDAPlace(fluid.dygraph.ParallelEnv().dev_id)
-        with fluid.dygraph.guard(place=place):
-
-            # prepare the data parallel context
-            strategy=dygraph.prepare_context()
-
-            linear = Linear(1, 10, act="softmax")
-            adam = fluid.optimizer.AdamOptimizer()
-
-            # make the module become the data parallelism module
-            linear = dygraph.DataParallel(linear, strategy)
-
-            x_data = np.random.random(size=[10, 1]).astype(np.float32)
-            data = to_variable(x_data)
-
-            hidden = linear(data)
-            avg_loss = fluid.layers.mean(hidden)
+        import paddle
+        import paddle.distributed as dist
 
-            # scale the loss according to the number of trainers.
-            avg_loss = linear.scale_loss(avg_loss)
+        def train():
+            # 1. initialize parallel environment
+            dist.init_parallel_env()
 
-            avg_loss.backward()
+            # 2. get current ParallelEnv
+            parallel_env = dist.ParallelEnv()
+            print("rank: ", parallel_env.rank)
+            print("world_size: ", parallel_env.world_size)
 
-            # collect the gradients of trainers.
-            linear.apply_collective_grads()
+            # print result in process 1:
+            # rank: 1
+            # world_size: 2
+            # print result in process 2:
+            # rank: 2
+            # world_size: 2
 
-            adam.minimize(avg_loss)
-            linear.clear_gradients()
+        if __name__ == '__main__':
+            # 1. start by ``paddle.distributed.spawn`` (default)
+            dist.spawn(train, nprocs=2)
+            # 2. start by ``paddle.distributed.launch``
+            # train()
     """
 
     def __init__(self):