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+
+ MGD3: PARALLEL 3-D MULTIGRID PACKAGE
+
+ Author: Bernard Bunner (bunner@engin.umich.edu)
+ January 1998
+
+ 
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mgd3 is a parallel 3-d multigrid program which solves the
non-separable Poisson equation:

d(cof(x,y,z)*d(phi)/dx)/dx+d(cof(x,y,z)*d(phi)/dy+
d(cof(x,y,z)*d(phi)/dz)/dz=rhs(x,y,z)

on a staggered grid. The rectangular domain has a constant
grid step in all directions and is decomposed into 
rectangular subdomains. In discretized form, this equation
can be written as

  [ cof(i+1/2,j,k)*(phi(i+1,j,k)-phi(i,j,k))
   -cof(i-1/2,j,k)*(phi(i,j,k)-phi(i-1,j,k)) ] / (dx*dx)
+ [ cof(i,j+1/2,k)*(phi(i,j+1,k)-phi(i,j,k))
   -cof(i,j-1/2,k)*(phi(i,j,k)-phi(i,j-1,k)) ] / (dy*dy)
+ [ cof(i,j,k+1/2)*(phi(i,j,k+1)-phi(i,j,k))
   -cof(i,j,k-1/2)*(phi(i,j,k)-phi(i,j,k-1)) ] / (dz*dz)
=  rhs(i,j,k)

Periodic, Neumann and Dirichlet are possible. The code is
written in Fortran 77 with the MPI library. A Makefile is
provided for the IBM-SP2.