CTITLEOPFILT -- COMPUTE SOLUTION TO WEINER-LEVINSON EQUATIONS           00010000
C***********************************************************************
C                 COPYRIGHT ATLANTIC RICHFIELD COMPANY 1991            *
C***********************************************************************
CA    AUTHOR        STU NELAN                                           00020000
CA    DESIGNER      STU NELAN                                           00030000
CA    LANGUAGE      FORTRAN                                             00040000
CA    SYSTEM        IBM (SEE CRAY SYSTEM LIBRARY)                       00050000
CA    WRITTEN       02-19-86                                            00060000
C     REVISED       04-28-87 ESN.  CALL SWLEV INSTEAD OF LEVINE.        00070000
CA                                                                      00080000
CA                                                                      00090000
CA    CALL OPFILT (M, A, B, C, R)                                       00100000
CA         INPUT   M = ORDER OF SYSTEM OF EQUATIONS                 I4  00110000
CA         OUTPUT  A = OUTPUT VECTOR OF FILTER COEFFICIENTS         R4  00120000
CA         INPUT   B = INFORMATION AUTO-CORRELATION VECTOR          R4  00130000
CA         INPUT   C = SCRATCH VECTOR OF LENGTH 2M                  R4  00140000
CA         INPUT   R = SIGNAL AUTO-CORRELATION VECTOR               R4  00150000
CA                                                                      00160000
CA                                                                      00170000
CA       OPFILT SIMULATES THE CRAY OPFILT ROUTINE TO COMPUTE THE        00180000
CA       SOLUTION TO THE WEINER-LEVINSON SYSTEM OF LINEAR EQUATIONS     00190000
CA       TA=B WHERE T IS A TOEPLITZ MATRIX IN WHICH ELEMENTS ARE        00200000
CA       DESCRIBED BY                                                   00210000
CA                T(I,J) = R(K)  FOR  IABS(J-I)+1 = K                   00220000
CA                               AND  K = 1,...,M                       00230000
CAEND                                                                   00240000
      SUBROUTINE OPFILT (M, A, B, C, R)                                 00250000
C                                                                       00260000
      REAL  A (1)                                                       00270000
      REAL  B (1)                                                       00280000
      REAL  C (1)                                                       00290000
      REAL  R (1)                                                       00300000
C                                                                       00310000
C     CALL LEVINE (M, A, R, B, C, C(M+1))                               00320000
      J = 1                                                             00330000
      I = LOC(C(1))                                                     00340000
      IF ((I/8)*8 .NE. I) J = 2                                         00350000
      CALL SWLEV (R, 1, B, 1, A, 1, M, C(J), 3*M)                       00360000
C                                                                       00370000
      RETURN                                                            00380000
C                                                                       00390000
      END                                                               00400000