I did math in undergrad and I am now going the computer science PhD route. I think basic math really helps and some fields like combinatorial optimizations are

I did math in undergrad and I am now going the computer science PhD route. I think basic math really helps and some fields like combinatorial optimizations are good as well, but most of mathematics is only useful for pure mathematicians and physicists. Except for niche fields like topological data analysis, I have yet to see any application of homological algebra, algebraic geometry or PDEs in computer science.