* optimize sum op

fuse multi eigen kernel calls into one cuda kernel.
refine code

test=develop.
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* Refine code.

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* Refine code according to comments.

test=develop

* refine code

delete sum_op_gpu.h
test=develop

* Fix test error.

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* refine code in format.

test=develop.

* refine code

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

* refine code

test=develop
Signed-off-by: Nzhaoyuchen <zhaoyuchen01@baidu.com>

test=develop

*  fix mkdir conflict

*  fix load/save lookup tables

 test=develop

* add lookup_table_utils

* fix load optimize vars on pserver

* delete lookup table utils

* fix save and load lookup tables

* fix load optimizer var

* fix load optimizer var, test=develop

* fix python 3 style, test=develop

* move lookup_table_utils to contrib utils

* add fp16 backward support
test=develop

* add sum_op fp16 test

* disable test_dist_save_load
test=develop

* add check_grad for sum

* add unit test for softmax_grad fp16
test=develop

* add scale_op unit test

* add mul_grad_op unit test for fp16

* add cross_entropy_grad and eman_grad unit test for fp16
test=develop

* fix cross_entropy unit test

* add pool2d fp16 unit test

* refine conv2d fp16 unit test
test=develop

* refine activation unit test
test=develop

* fix ci
test=develop

* follow zhihong's comment, copy from https://github.com/PaddlePaddle/Paddle/pull/12796
test=develop

test=develop

* add dist ut for text_classification

* add dist ut for text_classification

* add simnet bow unittest

* add dist ut for simnet bow

* add trainning data url for simnet bow

* add trainning data url for simnet bow

* modify simnet test_reader to train reader

* add test_dist_ctr

* test_dist_ctr can run now

* dense update is good

* add unit test for selected rows

* debug unit test

* fix dist sparse update problem

* Constant args at init

* optimize code

* simnet optimize

* fix DebugStringEx

* optimize sum_op.h

* add ScaleOpVarTypeInference

* clean code

* fix test_dist_transpiler.py

* code optimize

* modify delta

* fix sparse update bug

* dist test use one cpu

* update some data

* remove unused code

* add use cuda config

* unit test fix

* unit test fix

* unit test fix

* unit test fix

* dist_word2vec use CPU

* unit test fix

* unit test fix

* code clean

* code clean

* merge develop

* api spec update

* Revert: api spec update

* replace simnet data with fake

* replace simnet data with fake

* update dim

* add batch auc

* code clean

* code clean

* modify print to stderr

* update simnet delta -> 1e-5

* update RUN_STEP

* add use_reader_alloc

* add use_reader_alloc

* add use_reader_alloc

* modify delta

* add use_reader_alloc

* fix stderr write

* python3 compatibility

test=develop

* python3 compatibility, test=develop

* Update dist_text_classification.py

* test=develop

This reverts commit a6c8d6b9.

This reverts commit bd79e046, reversing
changes made to 6b4d290c.

This reverts commit bf3c3496.

* "cherry picked operators changes"

* "remove duplicated code"

* "add constant setter"

* "add get expected kernel"

* "fix ci"

* "add fill constant"

Fix sparse update memory error for distributed training

* Update tensor_util.h

* Update with moved TensorDesc

* Fix tensur_utils.cu

* Update

* Update

* Update

* Update

* Make tensor_util.cu a symbolic link

* dynamic send/recv selected rows

* update by comment

* fix by comment

* Polish sum_op support SelectedRows in_place

* test dist word2vec

* multiple trainers work

* Rename Tensor::CopyFrom to Tensor::Copy

* Fix CI

* Fix compile

There are mainly following fixes:

- take `DeviceContext` as the template parameter of math functors and OpKernel instead of `Place`
- remove `eigen_device` interface in base class  `DeviceContext`
- remove `GetEigenDevice` interface in `ExecutionContext` and base class `DeviceContext`
- remove unused `platform::EigenDeviceConverter`
- rename `REGISTER_OP_GPU_KERNEL` to `REGISTER_OP_CUDA_KERNEL`
- rename `USE_GPU_ONLY_OP` to `USE_CUDA_ONLY_OP`

* Add DataFeeder

A v2 API like data feeder for book demos.
We can feed data directly from reader.

* Fix CI

* Add an unittest for while/rnn op forward

* Add unittest for raw while op backward

* Fix CI

* Fix Proformance problem of enforce

* Fix missing `;` in code

* Fix CI

* "make global tensor function independently"

* "replace functor"

* "fix inline template error"

* "fix tensor array with CopyFrom"

* "fix other case use CopyFrom"

* "move the op interface hardly"

* "fix operators"

* "fix typo"

* "delete dynamic recurrent rnn and fix gru_unit in debugmode"

* "fix unique_ptr copy"

* "fix cuda copy"

* "fix namespace error"

* "removed nccl python test"

* "fix include error"

* "fix typo"

* fix copy util test