Communication buffers size enhancement

[e-ago]

In my asynchronous implementation ( https://github.com/e-ago/CoMD-CUDA-Async ) using runs with parameters like "-e -x 80 -y 80 -z 80" with up to 16 process I noticed that after the first atom exchange function, the size of the communication buffers in the force exchange function never change; however the size is calculated again during each force exchange function call.

Therefore, after the first atom exchange, I always used the same buffer size and without having any crash.
Can this improvement be used in the most general case? (i.e. all the type of executions?)