Improve memoize
Improve memoize

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