Hans Johnston May 23 2004

   poiss2d.f solves a 2D Poisson eqn., periodic in x, using a
Fourier/Chebyshev spectral method, exactly as did the MATLAB code
I sent previously.  Everything is written in DOUBLE PRECISON, so
there is no need for any special compiler options.  These 3 files
comprise a completely self contained code (other than intrinsics.
mylapack.f takes care of the Linear Algebra stuff, and myfftD.f
the REAL FFT stuff.  I will use FFTW in the future, but for now
the rotuines form VFFTPK will be fine.

  Take a look.  I hope this helps further 'the cause'.  The code
only handles homogeneous Dirichlet BC as is, but modifying for other
Dirichlet BC and Neumann BC should be straightforward.