SLATEC Routines --- PRODP ---

*DECK PRODP
      SUBROUTINE PRODP (ND, BD, NM1, BM1, NM2, BM2, NA, AA, X, Y, M, A,
     +   B, C, D, U, W)
C***BEGIN PROLOGUE  PRODP
C***SUBSIDIARY
C***PURPOSE  Subsidiary to BLKTRI
C***LIBRARY   SLATEC
C***TYPE      SINGLE PRECISION (PRODP-S, PROCP-C)
C***AUTHOR  (UNKNOWN)
C***DESCRIPTION
C
C PRODP applies a sequence of matrix operations to the vector X and
C stores the result in Y (periodic boundary conditions).
C
C BD,BM1,BM2 are arrays containing roots of certain B polynomials.
C ND,NM1,NM2 are the lengths of the arrays BD,BM1,BM2 respectively.
C AA         Array containing scalar multipliers of the vector X.
C NA         is the length of the array AA.
C X,Y        The matrix operations are applied to X and the result is Y.
C A,B,C      are arrays which contain the tridiagonal matrix.
C M          is the order of the matrix.
C D,W,U      are working arrays.
C IS         determines whether or not a change in sign is made.
C
C***SEE ALSO  BLKTRI
C***ROUTINES CALLED  (NONE)
C***REVISION HISTORY  (YYMMDD)
C   801001  DATE WRITTEN
C   891214  Prologue converted to Version 4.0 format.  (BAB)
C   900402  Added TYPE section.  (WRB)
C***END PROLOGUE  PRODP