Continue work on main mpi algotirhm
Add requests array to the context struct
Add receive phase to the main algorithm
Add send part to the main algorithm
Add computation of the union of counters
Merge branch 'master' into parallel
Add function to load partial views of the graph.

This function will be used by processes to load the partial view of the
graph they are responsible for.
Extract rank computation from loading function.

Now the rank of the processor is computed outside the function that
loads the partial view of the graph
Fix the position where requests number is checked
Fix a bug when performing counter union
Add check on return code of MPI_Init
Fix an invalid free