GPU with Ressource Acquisition Is Initialization

Created by: cypox

Restructured the code to initialize GPU memory only at start and free the memory at the very end.

I tested this branch on single and 2 nodes. The execution time should also be a smidge faster.

gpu-raii: 32.25 19.86 20.95 20.42

gpu-hackathlon: 33.46 20.50 21.05 20.52