* Add Lookahead and ModelAverage Optimizer (#30004)

* test=develop, add model_average and lookahead

* Improve Index select cuda kernel (#30139)

* test=develop, add index_select_cuda kernel

* fix syncbn convet

* add unittest

* Simplify the options of spawn based on fleetrun (#30144)

* Simplify the options of spawn based on fleetrun

* polish details

* polish doc details

* cleanup enum test=develop (#29294)
Co-authored-by: Ngongweibao <weibao.gong@gmail.com>

* Support storage of large parameters (#29988)

* 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'

* Extend the timeout for the (#30151)

* Improve performance of elementwise_add grad op (#29187)

* pass stop_gradient for cast op

* improve performance of elementwise_add grad

* use tensor copy async

* dygraph branch

* fix dygraph branch

* add ut

* make gelu fp16 computing more robust (#29484)

* Add fast path for dropout when p == 0  (#29553)

* add fast path for p == 0 in dropout

* add ut

* Layer norm fp16 (#29169)

* add fp16 for layer_norm op

* revert layernorm api

* fix forward

* fix forward

* fix backward for layernorm with fp16

* fix unit test for layernorm with fp16

* fix with_mkldnn compile error for layernorm with fp16

* 1. revert to PADDLE_ENFORCE_NOT_NULL, 2. change static_cast<float> to static_cast<U>

* fix with_mkldnn compile error for layernorm with fp16

* fix with_mkldnn compile error for layernorm with fp16
Co-authored-by: Nzhiqiu <chenqiuliang@baidu.com>

* fix layer_norm accuracy (#29434)

* Layernorm opt (#29522)

* layernorm fw opt

* layernorm bw opt

* fix typo, test=develop

* remove const dim3 for windows CI compatibility

* merge develop
Co-authored-by: Nzlsh80826 <zlsh80826@gmail.com>

* Fix compile problem when cuda_arch < 6000 (#29576)

* fix compile problem when cuda_arch < 6000

* refine code

* refine code
Co-authored-by: Nzhiqiu <chenqiuliang@baidu.com>
Co-authored-by: Nzlsh80826 <zlsh80826@gmail.com>

Change-Id: Ia5279b0cbb6a5b3970aff66e9510e0d85efa70ce

* fix bn docs (#30096)

* add attribute for batch_norm (#29950)

* add attribute for batch_norm

* support dygraph in xpu place; test=develop

* fix cpu/gpu compile error; test=develop

* fix compile error; test=develop

* fix xpu compile error; testd=develop

* fix log test=release/2.0

* fix ut test=develop

* add fp16 check into max and avg pool (#29479)

* Add ReserveSpace in dygraph batch_norm. (#29221)

* Add ReserveSpace in dygraph batch_norm.

* Add unittest for reservespace

* add float16 into adaptive_avg_pool2d check list. (#29547)

[Cherry-Pick 2.0][Dynamic Inplace] Support ShareInplaceVersionCounterWith for C++ Tensor (#29842) (#30105)

Before this PR, SharePlaceHolderWith share Tensor between different C++ Variable, which meas sharing the data, shape, and inplace_version_counter_ of Tensor.
But in some cases, Sharing data and inplace_version_counter_ but not sharing shape is needed. For example, inplace op reshape, can't share shape.

This PR, discard SharePlaceHolderWith, and expose ShareInplaceVersionCounterWith for C++ Tensor.
This reverts commit b10ecd9d.

* Support ShareInplaceVersionCounterWith to share the same inplace version counter for VarBase

4 APIs: array_length, array_read, array_write, create_array，cherry-pick #29565

* add topo aware

* resource.h

* topo aware

* format

* [cherry-pick 2.0] Fix unitest test_slice (#29740)

Before this commit, test_slice use old api `dygraph_to_static_func` to use Dynamic-t-Static and use Executor explicitly，which is not recommended to users.
After fixed, use recommended API `paddle.jit.to_static` to replace `dygraph_to_static_func`, which won't trigger the random exception on coverage CI.

* [cherry-pick 2.0][Dy2Stat] Support grammar: for ele in var[idx] (#29541)

Support to transformfor ele in var stms in which var is a slice of Tensor.

* [cherry-pick 2.0][Dy2Stat] Fix bug for loop: a variable is used and created in loop, but used before created (#29769)

* fix ininite scale values (#29386)

* Support dygraph quant model (#29927)

* Avoid the scale to be infinity in quant2_int8_mkldnn_pass, test=develop
* support quantized model for paddle2.0 dygraph, test=develop
Co-authored-by: NWojciech Uss <wojciech.uss@intel.com>

Set FLAGS_selected_gpus for spawn.

When the child process starts, it will inherit the configuration of the main process and set the FLAGS once, but the environment variable has not been set at this time, which leads to the FLAGS_selected_gpus is keep same with mainprocess(usually empty), so manually update the flags here.

注：增加了一个单测，又移除了，单测打印显示CI机器nvidia-smi只有两张卡，需要大于两张卡才能测这个问题

* memory holder optimize

Change-Id: Ic91af8ac6f2853336d28a9fbbc5e8d0c57b5d05e

* memory holder optimize

Change-Id: I2fd1c14ecc17f5d5ce88b87890381ea801e6367f

* fix large scale memory holder

Change-Id: Ief0992b02b00220e16c72cc637a56e7b5788140f

* fix large scale memory holder

Change-Id: I910142a3952ead643a5604f8f80955f3e6efe655

* support deepcopy for Layer/Tensor/Paramerbase

* fix some code

* add distributed.split, test=develop

* update, test=develop

* update, test=develop (#29559)

* Disable gloo by default (#29805)

* update, test=develop

* update, test=develop

test=develop

* add alias for upsample, test=develop

* add alias for upsample

* fix example

* update readme

* update readme test=document_fix

* fix doc bugs test=document_fix

* fix code bugs test=document_fix

* fix code bugs test=document_fix

* fix doc bugs test=document_fix

* fix doc bugs test=document_fix

* fix doc bugs test=document_fix

* fix cv2 rotation

* [Kunlun] PR1:Support one Kunlun card training in parallel executor (#29337)

* [Kunlun] PR2: Support MultiDevicePass and BKCL in parallel executor (#29574)

* [Kunlun] bug fix of PR2: Support MultiDevicePass and BKCL in parallel executor  (#29926)

* add bkcl.so in whl for kunlun (#29947)

* [Kunlun] bug fix of PR2: Support MultiDevicePass and BKCL in parallel executor  (#29961)
Co-authored-by: NQingshuChen <qingshu.chen714@gmail.com>

* [Complex] Add support for complex grad accumulated (#29889)

* add support for complex grad accumulated

* add unittest for coverage

* update test dtype

* remove useless blank line

* [Complex] Handle complex to real after type promotion (#29855)

* try to add fwd op input dtypes

* refactor base impl

* return tmp_ins after dygraph prepare data

* fix typo found in debug

* polish comment & add complex net test

* revert detail change

* fix unittest failed

* add complex kernel condition control

* fix xpu test failed & polish comment

* polish details by review comments

* Complex op test (#29753)

* delete no need to calculate inputs in dygraph op_test

* delete no need to calculate inputs in dygraph op_test

* change grad elementwise_mul for complex types (#29757)

* add conj op for complex types

* add conj for complex types

* add more test case

* add conj_op test

* modify conj api and impl

* add complex type for fill_constant_op xpu

* add setConstant for complex type

* remove complex conj test file

* user define grad for test_conj_op

* add test case for static mode of conj api

* modify conj doc

* change input args name to x

* remove useless codes

* conj support real types

* add conj test case for real number

* delete no need to calculate inputs in dygraph op_test

* delete no need to calculate inputs in dygraph op_test

* modify grad of mul for complex types

* fix the grads of inputs args order not match bug

* change the grad of div when complex types (#29804)

* change the grad of div when complex types

* fix the grads of inputs args order not match bug
Co-authored-by: Nchentianyu03 <chentianyu03@baidu.com>