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>

* cherry pick heter ps

* 　CMakeList

* [Inference] FLAGS_call_statck is turned on default when ON_INFER=ON

* cherry-pick 29828

* fix conv_transpose bug when padding=same

* [cherry-pick] cherry-pick of PR#29928

* delete paddle.metric.chunk_eval and paddle.metric.mean_iou

* delete paddle.nn.clip and paddle.nn.clip_by_norm

* delete paddle.nn.functional.activation.hard_sigmoid and paddle.nn.functional.activation.hard_swish

* [cherry-pick] cherry-pick of PR#29928

* fix extension import error

* support some shape in matmul and cast

* modify matmul

[Cherry-Pick 2.0][Dy2Stat] 1. Fix bug of for-range stmts. 2. Support that step value is negative in for-range stmts (#29519) (#29874)

1. Fix error in _build_cond_stmt of for-range stmts.

2. Support that step value is negative in for-range stmts

3. Fix code because of the diff between Py2 and Py3

* [Dy2stat] Enable jit.save to Save Without Running (#29579)

Enable jit.save to Save Without Running.

* Modify CublasHandleHolder to Fix Random Unittest Failure. test=develop (#29617)

Modify CublasHandleHolder from using PADDLE_ENFORCE_CUDA_SUCCESS to PADDLE_RETRY_CUDA_SUCCESS to fix random unittest failure. We checked that the unittest log showed CUDA allocation error at this file, which may due to GPU not enough. We fixed similar failure in the past, so we applied PADDLE_RETRY_CUDA_SUCCESS here.

* update to_tensor en docs

* feat: support check_nan_inf for kunlun device

* support kunlun stack

* minor

* add ps table (#29463)

* add ps table

Change-Id: I468a04bd071d21ff52654926fcf4d5f3da19e178

* add service (#29560)

* add service, remove ut on mac

* fix heter_profiler & add heter stop method

* fix code style

* merge pscore

Change-Id: Ie7f60d1cdde6755a0c29db26863c6283e9843d57

* fix cmake

Change-Id: I6773509a7b4ca79139ecc40b7bf3eb318ceff8bb

* fix conflit

Change-Id: I35575be0c96a8520f9d756ea7f1ff0b904a165ba

* fix conflit

Change-Id: Ic926ea0b0d67803226d51241397ba3b510226bfa

* add some feature for paddle.flops (#29572)

* fix flops (#29758)

* fix flops

* fix flops

* fix flops (#29818)

* add ps table (#29463)

* add ps table

Change-Id: I468a04bd071d21ff52654926fcf4d5f3da19e178

* add service (#29560)

* add service, remove ut on mac

* fix heter_profiler & add heter stop method

* fix code style

* add nearest_interp_v2 on kunlun

* add nearest_interp_v2 on kunlun
Co-authored-by: NTTerror <tangzhiyi11@users.noreply.github.com>

* fix fleet for multi-stream

* fix memcpy for ncclid

* use sync to solve move operation

* detele reduce_all reduce_any isfinite add all and any

* fix all and any example

* keep_dim to keepdim

* fix example code

* gen nccl id use socket (#29431)

* fix gen_nccl_id_op_helper compile failed, test=develop (#29614)