[fc417fc802]

> run a shader over them, and ignore the values you don't want to operate on

Use a compute shader. Run only as many invocations as you care about. Use explicit indexing in the shader to fetch and store.

Obviously that doesn't make sense if you're targeting 90% of the slots in the array. But if you're only targeting 10% or if the offsets aren't a monotonic sequence it will probably be more efficient - and it involves explicit indexing.