* batch_norm momentum support variable. test=develop

* support dump param of model into afs (#20302)

* support dump param to afs
test=develop

* code style
test=develop

* code style
test=develop

* dump param
test=develop

* dump param
test=develop

* dump param
test=develop

* dump param
test=develop

* find lookup table in order (#20932)

test=develop

* cherry-pick
test=develop

* solve pslib core in stop worker
test=develop

* print table stat info for pslib
test=develop

* fix cache table bug, add save_paddle_inference_model, fix hdfs util bug (#21052)

* fix cache table bug
* add save_paddle_inference_model
* fix hdfs util bug
* test=develop

* fix several sparse table issuses (#20686)

* no longer need to define all embedding layers (no one less) of all slots in each program. make trainer_param repeated in ps.proto.
* add find_distributed_lookup_table_grads instead of hard code GRAD
* support embedding stop gradient. push sparse has error before fix this.* 
* fix fill sparse, skip slots which do not have embedding. each slot's embedding in a sparse table should be used in all training programs before fix this.
* fix pull sparse, skip slots which do not have embedding.
* fix collect feasign label info, skip slots which do not have embedding.
* support when there are multi sparse tables in one or multi training programs, each program can pull/push its own related sparse tables instead of all sparse tables.
* test=develop

* add copy table (#21086)

* copy some feasigns and corresponding embeddings from one sparse table to another
* copy all feasigns and corresponding embeddings from one sparse table to another
* copy all dense params from one table to another
* copy some local vars to other local vars

* fix fs_client_param bug (#21212)

* fix fs_client_param bug， user can set this config through fleet_desc_file or fleet config
* test=develop

* fix fleet util bug (#21254)

* fix fleet util bug in save paddle inference model
* test=develop

* Fix gradients (#20857)

* fix_gradients

* fix_gradients, test=develop

* fix instance norm (#21042)

* fix instance norm

* update unitest,test=develop

* fix_bn

* revert unittest,test=develop

* add input type and input data type check for Print_op test=develop (#21250)

* add input type and input data type check for Print_op test=develop

* cherry-pick error info check of Print_op for release1.6 test=develop

* cherry-pick error info check of Print_op for release1.6 test=develop

* fix bug of issue #21259 (#21287)
pass the argument `allow_out_of_range` of one_hot op to c++ back end.

* [cherry-pick] All elements in attr(shape) of crop_tensor can be -1 and int32/64 kernel registered (#20756)

* All elements in attr(shape) of crop_tensor can be -1, test=develop, test=document_preview

* fix the bug that attr(offsets) should be initialized, test=develop

* [cherry-pick] maxout supports channel_last input (#20846)

* maxout support channel_last input, test=develop

* modified details of Input(X) and Attr(groups, axis) in doc, test=develop

* [cherry-pick] lrn supports channel_last input, test=develop (#20954)

* fix elementwise_mod FP kernel. test=develop

* fix unittest. test=develop

[cherry-pick]fix bug in pool/conv/conv_transpose: UpdatePaddingAndDilation, _get_padding_with_SAME and conv2dtranspose_forward_naive. (#20997) (#21225)

* fix bug in pool/conv/conv_transpose:
    1. It should be stride[i] not stride[0] in UpdatePaddingAndDilation;
    2. fix bug of func  _get_padding_with_SAME in test_conv/conv_transpose_op.py;
    3. fix bug of the computation process in function conv2dtranspose_forward_naive.
    test=release/1.6

test=release/1.6

TODO: fix cudnn_conv and re-enable it

test=develop
test=release/1.6

* Add asymetric padding support for mkldnn pooling
test=develop

* Add asymetric padding support for mkldnn conv
test=develop

* Add asymetric padding support for mkldnn conv_transpose
test=develop

* fix uniform random; test=develop

* add uniform random test; test=develop

* [cherry-pick]fix bug in reshape: (#20781)

consider the situation that shape of input can contain more than one -1.

* [cherry-pick]support Tensor for split and concat, support -1 in num_or_sections, add check num_or_sections (#20780)

* improve split and concat op:
1. support Tensor for argument 'dim' in split op.
2. support Tensor for argument 'axis' in concat op.
* redefine function GetDataFromTensor and set unknown output shape to - 1.
* add check: Attr(sections) match Input(X).
* support Tensor for attr(sections) and attr(sections) can contain -1.
* modify error message and fix bug for concat and call Resize only when necessary.
test=release/1.6

* [cherry-pick]improve unsqueeze op to support int, Tensor for argument axes (#20824)

* improve unsqueeze op to support int, Tensor and Tensor list for argument axes.
* call Resize only when necessary. test=release/1.6

* [cherry-pick]Compatible int32 and int64 for attr in concat/split/unsqueeze. test=release/1.6 (#20912)

cherry-pick1.6 simplify master+patch，remove ins when size != merge_size or has conflict slot  (#20941)

* simplify master+patch，remove ins when size != merge_size or has conflict slot
* test=develop

* add check nan / inf in downpour worker during training
* test=develop

* update pserver decay blocks

* update distributed notify handler

[cherry-pick] keep the size of symmetric padding is 2 for 2d and 3 for 3d. test=release/1.6 (#20903) (#20939)

* Fix Paddle Cloud role maker (#20860)

- fix jit::matmul bug 

input x, shape(m, k), weight, shape(k, n) 

* bug fix, test=develop

* Serialize to pickle format (#20820)

test=develop

* save load problem fix and new feature add (#20823)

* 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=document_fix

* test=release/1.6

test=release/1.6 test=document_fix

* add support for __get_item__ of Variable test=develop

* update the infer shape of matmul,  test=release/1.6

* add unittests of matmul, test=release/1.6

* change func names, test=release/1.6

* test=develop, communicator_is_sgd_optimizer flags