* add pure fp16 major function in auto_cast & tracer

* support master weight in dygraph for pure fp16

* check mix dtype of fp16&fp32 for check_finite_and_unscale op

* change pure fp16 funtion name

* refine some bug in auto_cast

* refine auto_cast interface logic

* add param _casted_by_pure_fp16 for class Layer

* support state_dict hook for save model by user appointed dtype in pure_fp16_decorator

* refine pure_fp16_decorator as decorator

* add unittest

* add comment

* add comment

* support recompute

* add comment for auto_cast and decorator

* support to_static_state_dict for paddle.jit.save

* unlimite models num and optimizers num

* add lookup_table in black_list

* fix momentum and layer state_dict

* fix bug in layer state_dict

* fix bug in layer state_dict_helper

* refine unittest

* refine test_momentun_op

* refine interface and some code

* refine amp_decorator interface

* refine pure fp16 interface

* refine master weight interface

* support grad group

* fix single card condition

* sharding support dp

* sharding support mp

* sharding support pp

* add cache for send_recv

* add eval_batch for pipeline

* add eval batch for pipelineparallel

* add style code

* fix bug of py36 import

* add recompute for pp

* add recompute offload

* add recompute partition

* add save/load for pipelineparallel

* add save/load

* fix bug of p2p for partial

* fix error

* add layer segment

* add segement for transformer

* add utest

* support 1f1b for pipeline

* add utest

* add send_partial/recv_partial

* support amp for pp

* fix logger

* add scatter-gather opt

* fix topo for pp

* rename function

* add amp support for pp

* add amp untest

* dygraph sharding

* update unitest hybrid_parallel_communicate_group

* add pplayer

* add sharedlayerdesc

* add parallel_cross_entropy

* add grad for crossentropy

* fix cross entropy

* fix c_split bug

* fix utest

* add c_embedding for tensorparallel

* fix pipeline

* fix mp pp dp

* fix utest of hybrid parallel

* add utest for tuple

* fix precision of mp

* fix bug of seed

* fix dp

* print group

* update, test=develop

* fix amp bug

* fix name of wordsize

* fix model parallel

* rm parallel_help.py

* add embedding

* add pp dygraph, test=develop

* add pipeline layer

* add clip/check

* add amp & clip grad in dygraph

* add logging

* support dp & mp

* add model parallel support in dygraph