CUDA streams don’t magically speed-up your code. They won’t speed-up most use cases. Mostly they are useful for overlapping copying with compute. They may also be useful if your kernels do not use all the SMs and are not all completely memory bound.
Most likely this is not the case for your code, but it’s hard to guess what the limiting factor is because you don’t specify X, A, B, etc. or measuretime().