* add multiprocess for dygraph data loader, test=develop

* polish code & add safe gurad, test=develop

* refactor dygraph dataloader & add signal handler, test=develop

* fix member initializer compile error on ci, test=develop

* fix member initializer compile error one more, test=develop

* remove useless config, test=develop

* skip windows incompatible problem, test=develop

* add unittest for coverage, test=coverage

* add more exception unittest case, test=develop

* deal with signal handler coverage, test=develop

* polish code & add signal handler tests, test=develop

* deal with coverage ci problem, test=develop

* split data loader test & coverage ci fix, test=develop

* remove test_imperative_data_loader_with_exception, test=develop

* remove singal process except test case, test=develop

* add exception tests again & remove sample list test, test=develop

* split normal and exception unittests to diff class, test=develop

* polish doc for use_multiprocess effect in static mode, test=develop

* DataParallel state dict don't include _layers.; test=develop

* add unitest of data parallel; test=develop

* add load state test; test=develop

* fix fsp_op, test=develop

* fix fsp grad op maker, test=develop

* update op_use_default_grad_op_maker.spec, test=develop

* fix save_dygraph with nonexistent dir
test=develop

* minor fix
test=develop

* fix unittest
test=develop

* fix static save
test=develop

enhanced ops: concat, nearest_interp, deformable_conv_v1, sequence_conv, transpose2, conv2d

* add all_parameters for Program, test=develop

* refine unittest, test=develop

* add example print result, test=develop

This reverts commit c7b03d30.

* test=develop, bug fix for sparse recorder

* add parameter check; test=develop

* change parameter name checker in dygraph guard; test=develop

* fix test layers error; test=develop

* revert some code to develop; test=develop

* fix exampel error; test=develop

* fix comment error; test=develop

* fix comment error; test=develop

* add NotImplementedError for multi optimizers used on multi-places . test=develop

* assert error only if num_devices>1. test=develop

* set test_optimizer_in_control_flow in CMakeLists for using multi-GPU.test=develop

* add backward gradient computation for op argsort test=developo

* use pre-commit test=develop

* add bn and relu fuse pass

* add op attr assert and dtype assert

* fix some inputs&&outputs bugs for the fused op and pattern.

* add the unittest for fuse_bn_act_pass. test=develop

* use normative enforce statements. test=develop

* add the cpu test. test=develop

* add the support of batch_size=1 for the bn with relu op. test=develop

* add the error type for paddle throws. test=develop

* add fused_batch_norm_act and fused_batch_norm_act_grad to op_has_unsed_vars_white_list. test=develop

* test Optimizer in dygraph, test=develop

* add optest for Optimizer in dygraph, test=develop

* fix adagrad optimizer, test=develop

* fix dpsgd optimizer, test=develop

* fix test_optimizer.py, test=develop

* fix dpsgd optimizer, this op only support cpu, test=develop

* add optest for optimizer, test=develop

* add description for dpsgd, test=develop

* add rmsprop to white_list in unused_var_check.cc, test=develop

* polish code style, test=develop

* polish code style, test=develop

* delete seed attribute for DpsgdOptimizer, test=develop

* change testing to debugging, test=develop

* use snake_cased Layer name

* add named_parameters and named_sublayers api

* add include_sublayers param, add unittest
test=develop

* fix named unittests
test=develop

* fix unittest
test=develop

* add api docs
test=develop

* arg fix
test=develop

* reserve rnn_impl name_scope for static graph
test=develop

* fix load static param
test=develop

* fix load static param
test=develop

* add clear_gradients for Optimizer, add api description, test=develop

* fix optest for optimizer's clear_gradient interface, test=develop

* add sample code, test=develop

* polish sample code, test=develop

* update layers, test=develop

* update layers for resnet, test=develop

* fix is_test attr, test=develop

* update cycle_gan, test=develop

* update reinforcement_learning, test=develop

* update ocr, test=develop

* fix bug, test=develop

* update PRelu arg
test=develop

* fix unittests
test=develop

* fix element mode alpha shape
test=develop

* split channel_or_input_shape arg
test=develop

* fix unittest
test=develop

* modify fc to linear in sample code, test=develop

* remove FC, test=develop

* remove warnings, test=develop

* drop fluid/imperative/README.md , test=develop

* change fc to linear, test=develop

* polish code style, test=develop

1. Add a new input named batch_roi_nums for prroi_pool_op. batch_roi_nums includes the number of roi for each image in batch when rois is Tensor. This information is saved in rois's lod when rois is LoDTensor.
2. add grad check to prroi_pool_op and solve unnormal X grad diff in CPU.

* modify test framework, test=develop

* fix test_fsp_op, test=develop

* up, test=develop

* up, test=develop

* up, test=develop

* add check for threshold, test=develop

* up, test=develop

* up, test=develop

* up, test=develop

* up, test=develop

* up, test=develop

* up, test=develop

* up, test=develop

* update, test=develop

* update, test=develop

* update, test=develop

enhanced ops: acos, asin, brelu, ceil, cos, elu, floor, hard_shrink,
hard_sigmoid, hard_swish, relu6, round, rsqrt, sin, softshrink,
cos_sim, cross_entropy, im2squence, kldiv_loss

* 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

* support dygraph structured name; test=develop

* add load static param unitest and fix save load; test=develop

* fix varBase import error; test=develop

* fix unitest error; test=develop

* add comment for parameter; test=develop

* fix uni test error; test=develop

* change parallel se-resnet; test=develop

* fix dygraph se resnext parallel test; test=develop

* remove useless code; test=develop

* remove useless code; test=develop