* support save/load single tensor

* compatibility modification according to unnittest

* Some python2.7 don't have 'copyreg' modules

* Handle a syntax error.

* Dealing with compatibility problems on Mac.

* Dealing with compatibility problems on Mac.

* edit unittest to improve coverage.

* Modify the code according to the review comments

* Reduce redundant code.

* support for static graph loading dygraph state_dict

* edit code according to CI

* edit unittest

* edit unnittest

* delete redundant file

* edit code according to Comments

* edit english doc

* edit english doc

* edit English DOC.

* get/set_tensor->get/set_value; return_numpy=False

* get/set_tensor->get/set_value; return_numpy=False

* edit unnittest

* edit unnittest

* polish code.

* add default argument  for paddle.save/static.save

* edit documentation of

* Add comments for special processing for protocol=2 and protocol=3.

* Update python/paddle/fluid/io.py
Co-authored-by: Nlanxianghit <47554610+lanxianghit@users.noreply.github.com>
Co-authored-by: Nlanxianghit <47554610+lanxianghit@users.noreply.github.com>

* Avoid  bug on 'MAC python3.5/6'.

* Choose the saving method according to the OS.

* smaller length of '_unpack_saved_dict' for MAC OS.

* add version information of Python.

* Edit comment.

* Support storage of large parameters

* Reduce the complexity of the unittest

* Reduce the complexity of the unittest,commented out unittest for

* add unittest for static.save/load

* Increase the timeout threshold of 'test_static_save_load'

* Increase the timeout threshold of 'test_static_save_load'

* Increase the timeout threshold of 'test_static_save_load' and 'test_paddle_save_load'

* Increase the timeout threshold of 'test_static_save_load' and 'test_paddle_save_load'

* update conv2d & softmax to new xpu api
* test=kunlun

* remove useless comments
* test=kunlun

* remote softmax xpu op
* test=kunlun

* update kunlun softmax
* test=kunlun

* update xpu unitest
* test=kunlun

* fix elementwise_grad bug for kunlun
*test=kunlun

* add static_only for static api

* addd static_only for class init

* remove static_only for default_main_program

* remove creater_parameter & startup_program

* remove failed apis

* revert py_func import

* remove global scope

* remove some api

* remove cuda pinned place

* change load dict file one by one to warn

* add unittests for coverage

* polish error message

* fix cond error

* adjust kunlun header file
*test=kunlun

* update kunlun unittest
*test=kunlun

* update xpu unitest
* test = kunlun

* update xpu unittest
* test=kunlun

* update xpu unitest
* test=kunlun

add two paddle-2.0 apis: paddle.static.io.save_inference_model and paddle.static.io.load_inference_model (#28606)

* add two apis: paddle.static.io.save_inference_model and paddle.static.io.load_inference_mode, which are campatible with paddle.fluid.io.save_inference_model and paddle.fluid.io.load_inference_model respectively.

* add unittest for new save_inference_model and load_inference_model. test=develop

* enhance doc. test=develop

* add paddle.enable_static() to test_inference_model_io.py. test=develop

* remove paddle.readers API. test=develop

* Directory migration, test=develop

* Change imperative from paddle init to paddle framework, test=develop

* Fixed jit bug, test=develop

* default static mode, test=develop

* fixed format and create parameter belongs to framework, test=develop

* Fixed import package, test=develop

* fix __init__ format, test=develop

* fixed alias problem

* fixed paddle.enable_imperative problems, test=develop

* Add unittest

* delete install_check comment

* Fixed unittest timeout

* fixed unittest error

* move Program default_xx_program to static package

* optimize unittest method

* fixed framework __init__ format

* fixed jit path

* delete alias

* move jit to paddle

* Fixed unittest format

* fixed paddle.default_main_program

* Fixed save load API in paddle __init__.py

* fixed ci paddle.imperative.to_variable

Integrated Trainer of Parameter Server (API add `fluid.contrib.layers.sparse_embedding` only) (#22957)

* Integrated Trainer of Parameter Server

* enable load_program_state run in imperative mode; test=develop

* remove useless code; test=develop

test=develop

* test=develop, test=document_fix

* test=develop, test=document_fix
Co-authored-by: Nswtkiwi <1208425345@qq.com>

* fix error message, test=develop

* add unittest, test=develop

* add DataLoader, Dataset, BatchSampler

* add fluid.device_guard to specify the device type for Op

test=develop

test=develop

* enhance load program state; test=develop

* optimize commet; test=develop

* fix save_dygraph with nonexistent dir
test=develop

* minor fix
test=develop

* fix unittest
test=develop

* fix static save
test=develop

* enhance load interface; test=develop

* add uni test and add comment; test=develop

* fix converage; test=develop

* use path.joint replace "/"; test=develop

* windows debug; test=develop

* fix window unitest error; test=develop

* fix commet error; test=develop

* add model shuffix check; test=develop

* fix example error; test=develop

* copy stop_gradient property in clone, test=develop

* fix pruning issue, test=develop

* fix kLookupTablePath issue, test=develop

* sync program, test=develop

* copy subblocks, test=develop

* add unittests, test=develop

* add fake init for the trainer, fix large memory hold in the trainer
* do not merge recv vars from a remote endpoint, test=develop
* add recv and save op, merge slice var in one op, save memory
* remove hsigmoid with pull sparse, test=develop

* fix persistable;

* fix save load bugs; test=develop

* fix bug; test=develop

* add example for new io api; test=develop

* addd example; test=develop

test=develop