The function MPI_Wtime returns a floating point number of
seconds, representing elapsed wall-clock time since some time
in the past. Note that, unlike UNIX function clock,
MPI_Wtime does not return the CPU time. The time returned by
MPI_Wtime may be different for different nodes. Thus, the times
returned by third.c refer only to the master node.
In the next lesson we will demonstrate how to arm a program and obtain information about the behaviour of other nodes as well.