I'm facing a combinatorial optimization problem whose name I don't know but I presume to be quite common. I would be very grateful for any hint at a name or pointer to the literature.
I want to minimize a function $f$ returning a scalar which takes as argument $M$ points from a set $\mathcal{S} = \lbrace x_1,...,x_N \rbrace$ where $M < N$. In other words, the problem consists in selecting the subset of $M$ points that minimize $f$.

