improve the doc of DataFeeder and default_main_program (#18241)

* improve the doc of DataFeeder and default_main_program

* update API.spec, test=develop

paddle/fluid/API.spec

@@ -7,7 +7,7 @@ paddle.fluid.Program.list_vars (ArgSpec(args=['self'], varargs=None, keywords=No
 paddle.fluid.Program.parse_from_string (ArgSpec(args=['binary_str'], varargs=None, keywords=None, defaults=None), ('document', 'b6a7ffb239a30bf2ce58cfaca8d8b8d5'))
 paddle.fluid.Program.to_string (ArgSpec(args=['self', 'throw_on_error', 'with_details'], varargs=None, keywords=None, defaults=(False,)), ('document', '89acca639baf00f3ad08b9d827e81706'))
 paddle.fluid.default_startup_program (ArgSpec(args=[], varargs=None, keywords=None, defaults=None), ('document', 'ba609cb02e4e55e8d626723567ef1778'))
-paddle.fluid.default_main_program (ArgSpec(args=[], varargs=None, keywords=None, defaults=None), ('document', '06a5a8f649dfb8496c1f683c909db375'))
+paddle.fluid.default_main_program (ArgSpec(args=[], varargs=None, keywords=None, defaults=None), ('document', '853718df675e59aea7104f3d61bbf11d'))
 paddle.fluid.program_guard (ArgSpec(args=['main_program', 'startup_program'], varargs=None, keywords=None, defaults=(None,)), ('document', '78fb5c7f70ef76bcf4a1862c3f6b8191'))
 paddle.fluid.name_scope (ArgSpec(args=['prefix'], varargs=None, keywords=None, defaults=(None,)), ('document', '61660461e1f44e0480ca22fa8a482c41'))
 paddle.fluid.cuda_places (ArgSpec(args=['device_ids'], varargs=None, keywords=None, defaults=(None,)), ('document', '7f3068b82fc427bfa04b1af953610992'))
@@ -575,9 +575,9 @@ paddle.fluid.CUDAPinnedPlace.__init__ __init__(self: paddle.fluid.core_avx.CUDAP
 paddle.fluid.ParamAttr.__init__ (ArgSpec(args=['self', 'name', 'initializer', 'learning_rate', 'regularizer', 'trainable', 'gradient_clip', 'do_model_average'], varargs=None, keywords=None, defaults=(None, None, 1.0, None, True, None, False)), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))
 paddle.fluid.WeightNormParamAttr.__init__ (ArgSpec(args=['self', 'dim', 'name', 'initializer', 'learning_rate', 'regularizer', 'trainable', 'gradient_clip', 'do_model_average'], varargs=None, keywords=None, defaults=(None, None, None, 1.0, None, True, None, False)), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))
 paddle.fluid.DataFeeder.__init__ (ArgSpec(args=['self', 'feed_list', 'place', 'program'], varargs=None, keywords=None, defaults=(None,)), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))
-paddle.fluid.DataFeeder.decorate_reader (ArgSpec(args=['self', 'reader', 'multi_devices', 'num_places', 'drop_last'], varargs=None, keywords=None, defaults=(None, True)), ('document', 'be47d7e07824b4281da77472846955ac'))
+paddle.fluid.DataFeeder.decorate_reader (ArgSpec(args=['self', 'reader', 'multi_devices', 'num_places', 'drop_last'], varargs=None, keywords=None, defaults=(None, True)), ('document', '449ec75d35b3498091908714e35e6686'))
 paddle.fluid.DataFeeder.feed (ArgSpec(args=['self', 'iterable'], varargs=None, keywords=None, defaults=None), ('document', 'ce65fe1d81dcd7067d5092a5667f35cc'))
-paddle.fluid.DataFeeder.feed_parallel (ArgSpec(args=['self', 'iterable', 'num_places'], varargs=None, keywords=None, defaults=(None,)), ('document', 'c312743c910dda1c3a9c6637ac30187f'))
+paddle.fluid.DataFeeder.feed_parallel (ArgSpec(args=['self', 'iterable', 'num_places'], varargs=None, keywords=None, defaults=(None,)), ('document', '334c6af750941a4397a2dd2ea8a4d76f'))
 paddle.fluid.clip.ErrorClipByValue.__init__ (ArgSpec(args=['self', 'max', 'min'], varargs=None, keywords=None, defaults=(None,)), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))
 paddle.fluid.clip.GradientClipByValue.__init__ (ArgSpec(args=['self', 'max', 'min'], varargs=None, keywords=None, defaults=(None,)), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))
 paddle.fluid.clip.GradientClipByNorm.__init__ (ArgSpec(args=['self', 'clip_norm'], varargs=None, keywords=None, defaults=None), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))

python/paddle/fluid/data_feeder.py

@@ -312,10 +312,12 @@ class DataFeeder(object):
                 
                 def reader(limit=10):
                     for i in range(limit):
-                        yield [random.random([784]).astype('float32'), random.randint(10)],
+                        yield [random.random([784]).astype('float32'), random.random([1]).astype('float32')],
                 
                 x = fluid.layers.data(name='x', shape=[1, 28, 28])
-                y = fluid.layers.data(name='y', shape=[1], dtype='int64')
+                y = fluid.layers.data(name='y', shape=[1], dtype='float32')
+                
+                fluid.layers.elementwise_add(x, y)
                 
                 feeder = fluid.DataFeeder(['x','y'], fluid.CPUPlace())
                 place_num = 2 
@@ -398,7 +400,7 @@ class DataFeeder(object):
                     for i in range(limit):
                         yield (random.random([784]).astype('float32'), random.random([1]).astype('int64')),
                 
-                place=fluid.CUDAPlace(0)
+                place=fluid.CPUPlace()
                 data = fluid.layers.data(name='data', shape=[1, 28, 28], dtype='float32')
                 label = fluid.layers.data(name='label', shape=[1], dtype='int64')
                 

python/paddle/fluid/framework.py

@@ -3706,7 +3706,8 @@ def default_main_program():
                 regularization=fluid.regularizer.L2Decay(1e-4))
             opt.minimize(loss)
             
-            print(fluid.default_main_program())
+            print(fluid.default_main_program().num_blocks)
+            print(fluid.default_main_program().blocks[0].var('image'))
     """
     return _main_program_