🚀 go-pugleaf

i hope that this is not a FAQ.  i have just gotten a undergraduate
engineering degree and am "attempting" to pursue some research in CFD
before i go on to grad school.  my apologies if this question
is inappropriate for this news group.

i am trying to do some CFD using 4th order compact finite differences
(classical Pade scheme).  this method of finite differencing yields
4th order accuracy in space with only a 3 point stencil, i.e. a
tridiagonal system.  the problem i have is that when i want to
implement periodic boundary conditions, i get a tridiagonal system
with two extra terms on the first and last rows.  i have been told
that a periodic version of the Thomas algorithm exists somewhere out
there.  i was wondering if anyone knew where i could get a hold of
such a routine, either in C or FORTRAN (preferably in C, though).

thanks in advance,

phil chung
-- 
typical disclaimer: blah! blah! blah!

pkchung@acm.princeton.edu