Simplified Gaussian elimination

INTERFACE:

    subroutine tridiagonal(N,fi,lt,value)

DESCRIPTION:

A linear equation with tridiagonal matrix structure is solved here. The main diagonal is stored on bu, the upper diagonal on au, and the lower diagonal on cu, the right hand side is stored on du. The method used here is the simplified Gauss elimination, also called Thomas algorithm.

USES:

    IMPLICIT NONE

INPUT PARAMETERS:

    integer, intent(in)                 :: N,fi,lt

OUTPUT PARAMETERS:

    REALTYPE                            :: value(0:N)

REVISION HISTORY:

    Original author(s): Hans Burchard & Karsten Bolding
    $Log: tridiagonal.F90,v $
    Revision 1.8  2010-09-17 12:53:53  jorn
    extensive code clean-up to ensure proper initialization and clean-up of all variables
    Revision 1.7  2006-11-24 15:13:41  kbk
    de-allocate memory and close open files
    Revision 1.6  2005/06/27 13:44:07  kbk
    modified + removed traling blanks
    Revision 1.5  2004/08/17 15:33:47  lars
    removed tabs
    Revision 1.4  2003/03/28 09:20:36  kbk
    added new copyright to files
    Revision 1.3  2003/03/28 08:06:33  kbk
    removed tabs
    Revision 1.2  2003/03/10 08:54:16  gotm
    Improved documentation and cleaned up code
    Revision 1.1.1.1  2001/02/12 15:55:58  gotm
    initial import into CVS