Now using scratch memory for sampling
Now using scratch memory for sampling


Former-commit-id: c2606bb74800cb8c06faa67d2818743ff2b05923
danielhers/dynet,clab/cnn,xunzhang/dynet,danielhers/dynet,xunzhang/dynet,shuheik/dynet,danielhers/dynet,chunyang-wen/dynet,danielhers/dynet,shuheik/dynet,xunzhang/dynet,shuheik/dynet,xunzhang/dynet,clab/cnn,shuheik/dynet,shuheik/dynet,clab/dynet,clab/dynet,shuheik/dynet,danielhers/dynet,clab/dynet,clab/cnn,clab/dynet,clab/dynet,shuheik/dynet,danielhers/dynet,clab/dynet,clab/dynet,chunyang-wen/dynet,danielhers/dynet,chunyang-wen/dynet,chunyang-wen/dynet