Should we allow dot product of sparse vectors?

[shyamupa]

Some student trying to use our package said why cannot he take dot product between two sparse vectors. Do we want to provide this? @KaiWeiChang

[KaiWeiChang]

Yes. We can provide it, although we do not need this functionality in our current learning algorithms. But it may be useful for other purposes. Could you implement it (it can be modified from the diff function).