`Metal.rand` with `Int8` and `Int16` are only generating positive numbers

[christiangnrd]

On main branch. Noticed while working on JuliaGPU/Metal.jl#321. Will still be relevant once JuliaGPU/Metal.jl#321 is merged as the MPSMatrixRandom generation is not always used. Unsigned integers and 32/64 bit variants seem unaffected.

Histograms:

Code:

using Metal, Plots, Random, Statistics

N=100000;

T = Int16;
a = rand(T, N);

ma = Metal.rand(T,N)

meana = mean(a)
meanma = mean(ma)

hist = plot()
histogram!(a;label="Array{$T}: $(mean(a))",α=0.2)
histogram!(hist, collect(ma);label="MtlArray{$T}: $(meanma)",α=0.2)

[maleadt]

Will still be relevant once JuliaGPU/Metal.jl#321 is merged as the MPSMatrixRandom generation is not always used.

So this is a bug with the GPUArrays RNG?

[christiangnrd]

I initially posted it here because I hadn't checked if it also happened with JLArrays yet but it does so yes this is a bug with GPUArrays RNG and this issue should probably be transferred.