C++*********************************************************************
C
C ACRS_2S.F
C            MOD PGI COMPILER BUG              FEB 19 2008 ArDean Leith
C            X RETURNS O                       APR 24 2009 ArDean Leith
C
C **********************************************************************
C=*                                                                    *
C=* This file is part of:   SPIDER - Modular Image Processing System.  *
C=* SPIDER System Authors:  Joachim Frank & ArDean Leith               *
C=* Copyright 1985-2010  Health Research Inc.,                         *
C=* Riverview Center, 150 Broadway, Suite 560, Menands, NY 12204.      *
C=* Email: spider@wadsworth.org                                        *
C=*                                                                    *
C=* SPIDER 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=* SPIDER 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=* You should have received a copy of the GNU General Public License  *
C=* along with this program. If not, see <http://www.gnu.org/licenses> *
C=*                                                                    *
C **********************************************************************
C
C  PURPOSE: CALCULATES   
C
C  PARAMETERS: X    FOURIER TRANSFORM                          (SENT)
C                      X=F(X )                                 (RET.)
C
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C--*********************************************************************

        SUBROUTINE ACRS_2S(X, LS,NSAM,NROW)

        COMPLEX          :: X(LS/2,NROW)

        DOUBLE PRECISION :: PI2

        NNNN = LS / 2

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

c$omp   parallel do private(i,j,ix,iy,argy,arg)
        DO J=1,NROW
           IY = J-1
           IF (IY .GT. (NROW/2))  IY = IY - NROW
           ARGY = SY * IY
           DO I=1,NNNN
              IX     = I-1
              ARG    = SX * IX + ARGY
              X(I,J) = CABS(X(I,J)) * CMPLX(COS(ARG),SIN(ARG))
            ENDDO
        ENDDO  
 
        INS = -1
        CALL FMRS_2(X,NSAM,NROW,INS)

        END