Fix default parameter
Fix default parameter

ysekky/chainer,ktnyt/chainer,wkentaro/chainer,keisuke-umezawa/chainer,niboshi/chainer,hvy/chainer,okuta/chainer,ktnyt/chainer,jnishi/chainer,niboshi/chainer,keisuke-umezawa/chainer,ronekko/chainer,niboshi/chainer,cupy/cupy,kikusu/chainer,jnishi/chainer,okuta/chainer,hvy/chainer,hvy/chainer,jnishi/chainer,wkentaro/chainer,ktnyt/chainer,aonotas/chainer,okuta/chainer,okuta/chainer,kikusu/chainer,jnishi/chainer,keisuke-umezawa/chainer,wkentaro/chainer,cupy/cupy,chainer/chainer,cupy/cupy,chainer/chainer,cupy/cupy,ktnyt/chainer,kashif/chainer,chainer/chainer,delta2323/chainer,anaruse/chainer,wkentaro/chainer,kiyukuta/chainer,chainer/chainer,niboshi/chainer,keisuke-umezawa/chainer,rezoo/chainer,tkerola/chainer,pfnet/chainer,hvy/chainer