Int8 Offsets

[simone-silvestri]

Hello, first of all, thanks for the beautiful package. Over at Oceananigans.jl and ClimaOcean.jl, we use offset arrays to store the underlying data of our Field types. However, now that we are increasing the complexity of the model, we are having increasingly frequent problems with GPU parameter space when launching kernels that require many offset array inputs.

We think that this has to do with the fact that offsets are Int64 types, which consume quite a lot of parameter space, however, we typically need offsets in the range of -10 .. 10, so Int8 would be enough for our scope.

However, it looks like the Int type is hardcoded in the OffsetArray type.

OffsetArrays.jl/src/OffsetArrays.jl

Line 114 in 5972e9e

offsets::NTuple{N,Int}

Is there a specific reason for having offsets as Int64s or would it be possible to allow flexibility in the sizes of the offsets?

In the latter case, could I attempt a PR allowing lower-sized offsets?

cc @glwagner