CTITLECRFFT2 -- COMPLEX-TO-REAL FFT                                     00010001
C***********************************************************************
C                 COPYRIGHT ATLANTIC RICHFIELD COMPANY 1991            *
C***********************************************************************
CA    AUTHOR        STU NELAN                                           00020001
CA    DESIGNER      STU NELAN                                           00030001
CA    LANGUAGE      FORTRAN                                             00040001
CA    SYSTEM        IBM (SEE CRAY SYSTEM LIBRARY)                       00050001
CA    WRITTEN       02-19-86                                            00060001
C     REVISED       XX-XX-XX III.  ...                                  00070001
CA                                                                      00080001
CA                                                                      00090001
CA    CALL CRFFT2 (INIT, IX, N, X, WORK, Y)                             00100001
CA         INPUT   INIT = INITIALIZATION SWITCH                     I4  00110001
CA         INPUT     IX = FFT SWITCH                                I4  00120001
CA         INPUT      N = SIZE OF FFT                               I4  00130001
CA         INPUT      X = INPUT VECTOR OF LENGTH N                  R4  00140001
CA         WORK    WORK = WORK ARRAY                                R4  00150001
CA         OUTPUT     Y = RESULT VECTOR OF LENGTH (N/2)+1 COMPLEX   C4  00160001
CA                                                                      00170001
CA                                                                      00180001
CA       CRFFT2 SIMULATES THE CRAY CRFFT2 ROUTINE.                      00190001
CAEND                                                                   00200001
      SUBROUTINE CRFFT2 (INIT, IX, N, X, WORK, Y)                       00210001
C                                                                       00220001
      REAL  WORK (1)                                                    00230001
      REAL  X    (1)                                                    00240001
      REAL  Y    (1)                                                    00250001
C                                                                       00260001
      IF (INIT .NE. 0) GO TO                                        80  00270001
C                                                                       00280001
      NP2 = N + 2                                                       00290001
      DO 10 I = 1, NP2, 2                                               00300001
   10 Y(I) = X(I)                                                       00310001
      IF (IX .LT. 0) GO TO                                          30  00320001
      DO 20 I = 2, NP2, 2                                               00330001
   20 Y(I) = X(I)                                                       00340001
      GO TO                                                         50  00350001
   30 DO 40 I = 2, NP2, 2                                               00360001
   40 Y(I) = -X(I)                                                      00370001
   50 CONTINUE                                                          00380001
      CALL S1FMAG (N, MAG, LFOUR)                                       00390001
C                                                                       00400001
      CALL S2DFI2 (MAG, Y,                                        *100) 00410001
C                                                                       00420001
      SCALE = SQRT(N*2.0)                                               00430001
      DO 60 I = 1, N                                                    00440001
   60 Y(I) = Y(I) * SCALE                                               00450001
C                                                                       00460001
   80 RETURN                                                            00470001
C                                                                       00480001
  100 CALL XDUMPX                                                       00490001
      GO TO                                                         80  00500001
C                                                                       00510001
      END                                                               00520001