Add cosine similarity operator.#3815

Merged

xinghai-sun merged 3 commits intoPaddlePaddle:developfrom

xinghai-sun:cos_sim_layer2

Sep 6, 2017

Commits on Sep 1, 2017

Add cos_sim op.
xinghai-sun
committed

Commits on Sep 2, 2017

Fix a bug causing wrong gradient results in cos_sim op.
xinghai-sun
committed

Commits on Sep 6, 2017

Update cos_sim operator by following reviewer's comments.
xinghai-sun
committed