* fix mem leak when converting Tensor to numpy array
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* remove unused unittest,test=develop

* follow comments, test=develop

* fix dygraph bug,test=develop

implement dygraph.parallel.DataParallel to hook reduce op.

* add doc for memory_optimize, test=develop

* update doc, test=develop

* doc update, test=develop

* Speed affine_channel_op unit testing
* Add check in tensor_py
* Fix ONLY_CPU Compiling

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* speedup gc and inplace softmax_with_cross_entropy_grad
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* refine models gpu mem
Merge skip vars and warning messages of mem opt
remove relu mem opt
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* follow comments
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* Add an option to enable the cache of expected kernel in train phase.
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* Change the default value of cache_expected_kernel to true.

* test fuse all_reduce

* Try to enable the runtime_context_cache pass in train phase.

* Put the append of runtime_context_cache pass ahead of multi_dev passes.
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add NCCLParallelContext for parallel dygraph

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* expose fuse broadcast ops

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* fuse optimizer

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* modify the interface of Pass::Allay
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* Polish code
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* Fix Travis CI
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* fix Pass::Apply interface
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* Fix Travis CI
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add include headers to fix travis-ci
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