C++*********************************************************************
C
C CENT_D.F
C        DOUBLE PRECSISON INCREASEs REPEATABILITY    JUN 05 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   CENT_D(X,NSAM,NROW,SNS,SNR)
C
C   PURPOSE: PHASE APPROXIMATION TO CENTER OF GRAVITY
C
C--*********************************************************************

         SUBROUTINE CENT_D(X,NSAM,NROW,SNS,SNR)

         REAL, DIMENSION(NSAM,NROW), INTENT(IN) :: X

         INTEGER, PARAMETER :: R_8 = SELECTED_REAL_KIND(P=8)
         REAL(KIND=R_8)     :: C,S,P,T,FI

         C = 0.0
         S = 0.0
         P = 8 * DATAN(1.0D0) / NSAM

c$omp    parallel do private(i,t,j),reduction(+:c,s)
         DO I=1,NSAM
             T = 0.0
             DO J=1,NROW
                T = T + X(I,J)
             ENDDO
            C = C + COS(P * (I-1)) * T
            S = S + SIN(P * (I-1)) * T
         ENDDO

         FI = ATAN2(S,C)
         IF (FI .LT. 0.0)  FI = FI + 8 * DATAN(1.0D0)
         SNS = FI / P  +1.0

         C = 0.0
         S = 0.0
         P = 8 * DATAN(1.0D0) / NROW

c$omp    parallel do private(i,t,j),reduction(+:c,s)
         DO J=1,NROW
            T = 0.0
            DO I=1,NSAM
                T = T + X(I,J)
            ENDDO

            C = C + COS(P * (J-1)) * T
            S = S + SIN(P * (J-1)) * T
         ENDDO

         FI = ATAN2(S,C)
         IF (FI .LT. 0.0)  FI = FI + 8 * DATAN(1.0D0)
         SNR = FI / P + 1.0

         END