SLATEC Routines --- POISN2 ---

*DECK POISN2
      SUBROUTINE POISN2 (M, N, ISTAG, MIXBND, A, BB, C, Q, IDIMQ, B, B2,
     +   B3, W, W2, W3, D, TCOS, P)
C***BEGIN PROLOGUE  POISN2
C***SUBSIDIARY
C***PURPOSE  Subsidiary to GENBUN
C***LIBRARY   SLATEC
C***TYPE      SINGLE PRECISION (POISN2-S, CMPOSN-C)
C***AUTHOR  (UNKNOWN)
C***DESCRIPTION
C
C     Subroutine to solve Poisson's equation with Neumann boundary
C     conditions.
C
C     ISTAG = 1 if the last diagonal block is A.
C     ISTAG = 2 if the last diagonal block is A-I.
C     MIXBND = 1 if have Neumann boundary conditions at both boundaries.
C     MIXBND = 2 if have Neumann boundary conditions at bottom and
C     Dirichlet condition at top.  (for this case, must have ISTAG = 1.)
C
C***SEE ALSO  GENBUN
C***ROUTINES CALLED  COSGEN, S1MERG, TRI3, TRIX
C***REVISION HISTORY  (YYMMDD)
C   801001  DATE WRITTEN
C   890531  Changed all specific intrinsics to generic.  (WRB)
C   891214  Prologue converted to Version 4.0 format.  (BAB)
C   900402  Added TYPE section.  (WRB)
C   920130  Modified to use merge routine S1MERG rather than deleted
C           routine MERGE.  (WRB)
C***END PROLOGUE  POISN2