* Finished ChannelWiseQuantDequantAbsMaxOp and Passed unittests.

* Finished channel-wise quantize strategy in imperative quantization.

* Added Cuda code of ChannelWiseQuantDequantMaxAbsOP
Add Cuda code of ChannelWiseQuantDequantMaxAbsOp

* Add quant_axis for channel_wise quant.

* fixed a bug in unnitests, which will not trigger axis = 1 case and cannot meet the coverage rate requirement.

* Added some assert infomation and fixed some coding style mistakes.

test=develop

* refine error msg in var_handle.h, test=develop

* refine all_reduce_op_handle

* fix some error msg

* refine variable_visitor

* refine threaded_ssa_graph_executor

* refine inplace related files

* refine executor related files

* refine fetch_op_handle.cc

* fix bug

* follow comments

* fix CIFAR & MNIST dataset. test=develop

* fix adam

* rmsprop support double

* fix fleet util and gloo

* fix worker endpoints

* fix

* fix UT

* fix gloo

* fix gloo

* update gloo

* update gloo

* update gloo

* update gloo

* update gloo

* fix gloo wrapper for hdfs

* add file gloo and UT

* fix UT

* fix UT

* fix UT

* hide public method of RoleMaker

* fix UT

* GPU fleetrun support gloo

* parameterserver fleetrun support gloo

* add UT

* add UT

* fix UT

* fix get server endpoint

* fix get server endpoint

* fix UT

* hide public method of rolemaker

* hide public method of rolemaker

* hide public method of rolemaker

* Update test_fleet_rolemaker_new.py

* hide public method of rolemaker

* hide public method of rolemaker

* fix worker endpoints

* fix gloo wrapper for hdfs

* GPU fleetrun support gloo

* parameterserver fleetrun support gloo

* fix get server endpoint

* Support python3.8

test=notest

* pass compatibility

* add compatibility registry

* add unittests for different padding

* add assert

* drop errmsg

* rm dependence of cv2

* fix cudnn dyload error

https://github.com/PaddlePaddle/Paddle/pull/27332

* Add env value to  log to stdout; 2.Add logger name

* Optimize log messages in dygraph-to-static

* Replace logging.warn and warnings.warn with logging_utils.warn

* fix op print error info problem. test=develop

* fix build error

* fix format

* fix error msg info

* fix format

and optimize the c++ implmentation of empty op as PR#26659 reviews,
and add bool for shape op.

* test=develop, util documents

paddle/fluid/operators/distributed_ops OP报错信息优化

* Fix install pr requirements.txt

* test=document_fix

Replace the 'spawn' start method with 'fork' start method for multiprocessing, on MacOS with python>=3.8 (#27317)

* Replace the 'spawn' start method with 'fork' start method for multiprocessing, on MacOs when python>=3.8

test=develop

enhance reduce op which can reduce tensor with arbitrary rank 

* update model.save_inference_model

* update doc for _save_inference_model, delete useless class in unittests

* make users not be able to set model._inputs be None

* update usage of Model class in unittests

* fix bugs of _verify_spec

* fix bugs of _verify_spec

* add unittest to increase coverage rate

* delete http.log

* update doc for save, remove requirments and limitations for using

* update doc for class Model

* fix floordiv

* Refine the unittest to support py38

    test=develop