a = a - rate*all_da b = b - rate*all_db 这两行之前应该需要 all_da = all_da/len(x) all_db = all_db/len(x)
a = a - rateall_da
b = b - rateall_db
这两行之前应该需要
all_da = all_da/len(x)
all_db = all_db/len(x)