What's it called when I want to choose items to fill container as full as possible - and what algorithm should I use?

Question

I have a problem as follows:

You are given item types of weight w1, w2, w3, .... wn; each item of these types is infinite in quantity.

You have a

Answer 1

If I have understood the problem correctly,

For xi belongs to {0,1, ... infinity} (i = 1 to n)
Maximize summation(wixi) (i = 1 to n)
subject to:
summation (wixi) <= W

You can solve it using an Integer Linear Programming Solver.

EDIT: as pointed out by Preston Guillot, it is a special case of knapsack problem where the value and mass of the items are the same.