save historical gradient info in separate file
save historical gradient info in separate file

shuoyangd/nematus,cshanbo/nematus,rsennrich/nematus,shuoyangd/nematus,cshanbo/nematus,EdinburghNLP/nematus,cshanbo/nematus,rsennrich/nematus,rsennrich/nematus,cshanbo/nematus,Proyag/nematus,shuoyangd/nematus,shuoyangd/nematus,rsennrich/nematus,Proyag/nematus,rsennrich/nematus,shuoyangd/nematus,Proyag/nematus,Proyag/nematus,Proyag/nematus,EdinburghNLP/nematus,EdinburghNLP/nematus,shuoyangd/nematus,cshanbo/nematus,cshanbo/nematus,EdinburghNLP/nematus,rsennrich/nematus,Proyag/nematus,EdinburghNLP/nematus,EdinburghNLP/nematus