this code is adapted from BoxLib/Tests/IOBenchmark
to test the burst buffer on cori.  only the write
is called (twice by the driver).  the read needs to
be finished.

this is a boxlib i/o test.
it writes and reads a multifab.

Usage:
iotest3d.Linux.g++.gfortran.MPI.ex
   [nfiles = nfiles]
   [maxgrid = maxgrid]
   [ncomps = ncomps]
   [nboxes = nboxes]
   [nsleep = nsleep]
   [ntimes = ntimes]
   [raninit = tf]
   [mb2    = tf]


the range [1,nprocs] is enforced for nfiles.
ncomps is the number of FAB components.
nboxes is the number of boxes in the multifab.
nsleep will sleep for nsleep seconds.
ntimes is the number of times to run the test.
raninit will initialize the multifab with random values.
mb2 will use 2^20 instead of 1.0e+06 to calculate megabytes.


example run:

mpiexec -n 4 bbiotest3d.Linux.g++.gfortran.MPI.ex nfiles=4 maxgrid=64 ncomps=16 nboxes=32 ntimes=4 raninit=true mb2=true