C ++********************************************************************
C                                                                      *
C                                                                      *
C                                                                      *
C **********************************************************************
C=* FROM: SPIDER - MODULAR IMAGE PROCESSING SYSTEM.   AUTHOR: J.FRANK  *
C=* Copyright (C) 1985-2005  Health Research Inc.                      *
C=*                                                                    *
C=* HEALTH RESEARCH INCORPORATED (HRI),                                *   
C=* ONE UNIVERSITY PLACE, RENSSELAER, NY 12144-3455.                   *
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C=* Email:  spider@wadsworth.org                                       *
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C=* This program is free software; you can redistribute it and/or      *
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C=* This program is distributed in the hope that it will be useful,    *
C=* but WITHOUT ANY WARRANTY; without even the implied warranty of     *
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C=* General Public License for more details.                           *
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C=* Free Software Foundation, Inc.,                                    *
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C=*                                                                    *
C **********************************************************************
C                                                                      *
C                                                                      *
C                                                                      *
C  PURPOSE:                                                            *
C                                                                      *
C  PARAMETERS:                                                         *
C                                                                      *
C        0         2         3         4         5         6         7 *
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C***********************************************************************

	SUBROUTINE  SHIFT_PF(X,NNNN,NSAM,NROW,NSLICE,SX,SY,SZ)

C
C  Shift (2)3-D in Fourier space
C  If SX and SY and SZ equal zero then no shift
C
	COMPLEX  X(NNNN,NROW,NSLICE)
	DOUBLE PRECISION  PI2

	IF(SX.EQ.0.0  .AND.  SY.EQ.0.0 .AND.  SZ.EQ.0.0)  RETURN
	PI2=8.0*DATAN(1.0D0)
c$omp parallel do private(i,j,k,arg,argy,argz,iz,iy,ix)
	DO    K=1,NSLICE
	IZ=K-1
	IF(IZ.GT.NSLICE/2)  IZ=IZ-NSLICE
	ARGZ=PI2*SZ*IZ/FLOAT(NSLICE)
	DO    J=1,NROW
	IY=J-1
	IF(IY.GT.NROW/2)  IY=IY-NROW
	ARGY=PI2*SY*IY/FLOAT(NROW)+ARGZ
	DO    I=1,NNNN
	IX=I-1
	ARG=PI2*SX*IX/FLOAT(NSAM)+ARGY
	X(I,J,K)=X(I,J,K)*CMPLX(COS(ARG),SIN(ARG))
	ENDDO
	ENDDO
	ENDDO
	END