Correcting the use of MPI_COMM_WORLD #306

Job	Run time
test (d2q9, float, same, true)	4m 15s
test (d2q9, float, same, false)	3m 55s
test (d2q9, float, half, true)	4m 7s
test (d2q9, float, half-shift, true)	4m 24s
test (d2q9, float, float, true)	4m 12s
test (d2q9, float, float, false)	3m 58s
test (d2q9, float, float-shift, true)	4m 6s
test (d2q9, float, float-shift, false)	4m 1s
test (d2q9, double, same, true)	4m 52s
test (d2q9, double, same, false)	4m 0s
test (d2q9, double, half, true)	4m 12s
test (d2q9, double, half-shift, true)	4m 19s
test (d2q9, double, float, true)	4m 29s
test (d2q9, double, float, false)	4m 1s
test (d2q9, double, float-shift, true)	4m 50s
test (d2q9, double, float-shift, false)	4m 6s
test (d2q9, double, double, true)	4m 15s
test (d2q9, double, double, false)	3m 57s
	1h 15m 59s

Provide feedback