Merge pull request #15995 from sneaxiy/release/1.3-fix-executor-doc

Fix release/1.3 Executor doc

Author: sneaxiy

python/paddle/fluid/executor.py

@@ -261,45 +261,42 @@ def _as_lodtensor(data, place):
 
 class Executor(object):
     """
-    An Executor in Python, only support the single-GPU running. For multi-cards, please refer to
-    ParallelExecutor.
-    Python executor takes a program, add feed operators and fetch operators to this program according
+    An Executor in Python, supports single/multiple-GPU running, and single/multiple-CPU running.
+    Python executor takes a program, adds feed operators and fetch operators to this program according
     to feed map and fetch_list. Feed map provides input data for the program. fetch_list provides
-    the variables(or names) that user want to get after program run. Note: the executor will run all
+    the variables(or names) that user wants to get after program runs. Note: the executor will run all
     operators in the program but not only the operators dependent by the fetch_list.
-    It store the global variables into the global scope, and create a local scope for the temporary
-    variables. The local scope contents will be discarded after every minibatch forward/backward finished.
-    But the global scope variables will be persistent through different runs.
-    All of ops in program will be running in sequence.
+    It stores the global variables into the global scope, and creates a local scope for the temporary
+    variables. The contents in local scope may be discarded after every minibatch forward/backward
+    finished. But the global scope variables will be persistent through different runs.
 
 
     Example:
-    .. code-block:: python
-        # First create the Executor.
-        place = fluid.CUDAPlace(0) if use_cuda else fluid.CPUPlace()
-        exe = fluid.Executor(place)
-
-        # Run the startup program once and only once.
-        # Not need to optimize/compile the startup program.
-        exe.run(fluid.default_startup_program())
-
-        # Run the main program directly without compile.
-        loss, = exe.run(fluid.default_main_program(),
-                        feed=feed_dict,
-                        fetch_list=[loss.name])
-        # Or, compiled the program and run. See `CompiledProgram` for more detail.
-        compiled_prog = compiler.CompiledProgram(
-            fluid.default_main_program()).with_data_parallel(
-            loss_name=loss.name)
-        loss, = exe.run(compiled_prog,
-                        feed=feed_dict,
-                        fetch_list=[loss.name])
+
+        .. code-block:: python
+
+            # First create the Executor.
+            place = fluid.CUDAPlace(0) if use_cuda else fluid.CPUPlace()
+            exe = fluid.Executor(place)
+
+            # Run the startup program once and only once.
+            # Not need to optimize/compile the startup program.
+            exe.run(fluid.default_startup_program())
+
+            # Run the main program directly without compile.
+            loss, = exe.run(fluid.default_main_program(),
+                            feed=feed_dict,
+                            fetch_list=[loss.name])
+            # Or, compiled the program and run. See `CompiledProgram` for more detail.
+            compiled_prog = compiler.CompiledProgram(
+                fluid.default_main_program()).with_data_parallel(
+                loss_name=loss.name)
+            loss, = exe.run(compiled_prog,
+                            feed=feed_dict,
+                            fetch_list=[loss.name])
 
     Args:
         place(core.CPUPlace|core.CUDAPlace(n)): indicate the executor run on which device
-
-    Note: For debugging complicated network in parallel-GPUs, you can test it on the executor.
-    They has the exactly same arguments, and expected the same results.
     """
 
     def __init__(self, place):
@@ -382,16 +379,19 @@ def _fetch_data(self, fetch_list, fetch_var_name, scope):
         ]
         return outs
 
+    '''
+    TODO(typhoonzero): Define "no longer use" meaning? Can user create
+    a new Executor for the same program and run?
+    TODO(panyx0718): Why ParallelExecutor doesn't have close?
+    '''
+
     def close(self):
         """
         Close this executor.
 
         You can no longer use this executor after calling this method.
         For the distributed training, this method would free the resource on PServers related to
         the current Trainer.
-        TODO(typhoonzero): Define "no longer use" meaning? Can user create
-        a new Executor for the same program and run?
-        TODO(panyx0718): Why ParallelExecutor doesn't have close?
 
         Example:
             >>> cpu = core.CPUPlace()