* move eigen/reduce.h imple into cpu/reduce.h

* ctx to dev_ctx

* change 'math' to 'math_kernel'

* fix compile bugs

* merge develop

* fix compile bugs

* fix compile bugs

* move reduce files by new rule

* add set header

* format code style

* merge develop and fix conflict

* merge develop and fix conflict
Co-authored-by: NYuanRisheng <yuanrisheng@baidu.com>

* move inner cast api to cast_kernel.h

* resolve conflit

* remove intype arg in cast kernel

* modify conj config in api.yaml by dictionary order

* rm unused code in cast_kernel.cu

* rename to api to copy_to

* revert needless change

* polish format

* add pten reduce kernel

* add reduce_sum kernel

* update attribute args and order

* make out dtype undefined

* fix empty input error

* merge develop branch

* rename sum as reduce function

* rename sum as reduce function

* fix reducekernelImpl args error

* add reduce cuda kernel

* modify dims type to const &

* remove unsed log

* fix reduce_all out eigen function error

* remove unused codes

* add the missing sum api define and testcase

* merge develop branch

* fix sum test axis value error

* replace pten mean kernel with reduce_mean

* revcover meam cuda to original implement