Use defaultdict in memory pool
Use defaultdict in memory pool

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