Improve basic math
Improve basic math

AlpacaDB/chainer,okuta/chainer,muupan/chainer,t-abe/chainer,ktnyt/chainer,hvy/chainer,keisuke-umezawa/chainer,niboshi/chainer,hvy/chainer,yanweifu/chainer,niboshi/chainer,cupy/cupy,masia02/chainer,keisuke-umezawa/chainer,anaruse/chainer,jnishi/chainer,keisuke-umezawa/chainer,cemoody/chainer,chainer/chainer,benob/chainer,cupy/cupy,hvy/chainer,jnishi/chainer,jnishi/chainer,niboshi/chainer,okuta/chainer,muupan/chainer,hidenori-t/chainer,tkerola/chainer,cupy/cupy,sinhrks/chainer,chainer/chainer,ysekky/chainer,wkentaro/chainer,chainer/chainer,cupy/cupy,tscohen/chainer,keisuke-umezawa/chainer,minhpqn/chainer,ktnyt/chainer,t-abe/chainer,umitanuki/chainer,wkentaro/chainer,benob/chainer,wkentaro/chainer,niboshi/chainer,sou81821/chainer,kikusu/chainer,wkentaro/chainer,tigerneil/chainer,laysakura/chainer,rezoo/chainer,kiyukuta/chainer,pfnet/chainer,jnishi/chainer,AlpacaDB/chainer,truongdq/chainer,ktnyt/chainer,kashif/chainer,1986ks/chainer,ktnyt/chainer,hvy/chainer,ikasumi/chainer,chainer/chainer,Kaisuke5/chainer,aonotas/chainer,kikusu/chainer,sinhrks/chainer,truongdq/chainer,ronekko/chainer,okuta/chainer,okuta/chainer,ytoyama/yans_chainer_hackathon,delta2323/chainer