C++*********************************************************************
C
C CCRD_3.F                       
C              PGI BUG                          FEB 10 2006 ArDean Leith
C              MOD PGI COMPILER BUG             FEB 19 2008 ArDean Leith
C              X RETURNS O                      APR 24 2009 ArDean Leith
C
C **********************************************************************
C=* FROM: SPIDER - MODULAR IMAGE PROCESSING SYSTEM.   AUTHOR: J.FRANK  *
C=* Copyright (C) 1985-2009  Health Research Inc.                      *
C=*                                                                    *
C=* HEALTH RESEARCH INCORPORATED (HRI),                                *   
C=* ONE UNIVERSITY PLACE, RENSSELAER, NY 12144-3455.                   *
C=*                                                                    *
C=* Email:  spider@wadsworth.org                                       *
C=*                                                                    *
C=* This program is free software; you can redistribute it and/or      *
C=* modify it under the terms of the GNU General Public License as     *
C=* published by the Free Software Foundation; either version 2 of the *
C=* License, or (at your option) any later version.                    *
C=*                                                                    *
C=* This program is distributed in the hope that it will be useful,    *
C=* but WITHOUT ANY WARRANTY; without even the implied warranty of     *
C=* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  *
C=* General Public License for more details.                           *
C=*                                                                    *
C=* You should have received a copy of the GNU General Public License  *
C=* along with this program; if not, write to the                      *
C=* Free Software Foundation, Inc.,                                    *
C=* 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.      *
C=*                                                                    *
C **********************************************************************
C
C  CCRD_3(LUN2,X,BUF,LS,NSAM,NROW,NSLICE)
C
C  PURPOSE: CALCULATES CIRCULAR CROSCORRELATION,  X= F(X*CONJG(Y))
C
C  PARAMETERS:  X      FOURIER TRANSFORM                  (SENT)
C                      F(X*CONJG(Y))                      (RET.)
C               BUF    I/O BUFFER                         (SENT)
C               LS     FOURIER NSAM DIMENSION             (SENT)
C               NSAM   READ DIMENSION                     (SENT)
C               NROW   NROW DIMENSION                     (SENT)   
C               NSLICE NSLICE DIMENSION                   (SENT)   
C
C23456789012345678901234567890123456789012345678901234567890123456789012
C--*********************************************************************

        SUBROUTINE CCRD_3(LUN2,X,BUF, LS,NSAM,NROW,NSLICE)

        COMPLEX          :: X(LS/2,NROW,NSLICE)
        COMPLEX          :: BUF(LS/2)

        COMPLEX          :: CTEMP
        DOUBLE PRECISION :: PI2

        NNNN = LS / 2
        LRS  = 2 * NNNN

        PI2  = 8.0 * DATAN(1.0D0)
        ITMP = NSAM / 2
        SX   = PI2 * FLOAT(ITMP) / FLOAT(NSAM)
        ITMP = NROW / 2
        SY   = PI2 * FLOAT(ITMP) / FLOAT(NROW)
        ITMP = NSLICE / 2
        SZ   = PI2 * FLOAT(ITMP) / FLOAT(NSLICE)

        NR   = 0

        DO K=1,NSLICE
           IZ = K-1
           IF (IZ .GT. (NSLICE/2))  IZ = IZ - NSLICE
           ARGZ = SZ * IZ

           DO J=1,NROW
              IY = J - 1
              IF (IY .GT. (NROW/2)) IY = IY - NROW
              ARGY = SY * IY + ARGZ
              NR   = NR + 1
              CALL REDLIN(LUN2,BUF,LRS,NR)

              DO I=1,NNNN
                 IX       = I - 1
                 ARG      = SX * IX + ARGY
                 CTEMP    = CMPLX(COS(ARG),SIN(ARG))
                 X(I,J,K) = X(I,J,K) * CONJG(BUF(I)) * CTEMP
              ENDDO
           ENDDO
        ENDDO

        INS = -1
        CALL FMRS_3(X,NSAM,NROW,NSLICE,INS)

        END