This code solves

   a alpha soln - b div (beta grad soln) = rhs,

where a and b are constants, alpha, beta, rhs, and soln are arrays.
It uses the linear solvers in this BoxLib release.

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To run on Hopper with IPM, set USE_IPM = TRUE in the GNUmakefile.
You may need to load the ipm module (and possibly others):

module load ipm

Then recompile the code.  This will create an executable file named

main3d.Linux.gcc.gfortran.MPI.ex

There is an example batch script named qsub.ipm.bat in this directory,
You will need to set a valid account number in order to run the example.

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Suggested Runs for O(100), O(1000), O(10K), O(100K):

1) 4**3: NPROCS = 64

2) 12**3: NPROCS = 1728

3) 24**3: NPROCS = 13824

4) 48**3: NPROCS = 110592

