source: palm/trunk/SOURCE/global_min_max.f90 @ 1

 SUBROUTINE global_min_max( i1, i2, j1, j2, k1, k2, ar, mode, value, &
                            value_ijk, value1, value1_ijk )

!-------------------------------------------------------------------------------!
! Actual revisions:
! -----------------
! 
!
! Former revisions:
! -----------------
! $Log: global_min_max.f90,v $
! Revision 1.11  2003/04/16 12:56:58  raasch
! Index values of the extrema are limited to the range 0..nx, 0..ny
!
! Revision 1.10  2003/03/16 09:39:21  raasch
! Two underscores (_) are placed in front of all define-strings
!
! Revision 1.9  2003/03/14 13:42:50  raasch
! IF clause extracted from loop which determines the absolut array maximum,
! because otherwise it prevents vectorization of that loop
!
! Revision 1.8  2002/12/19 14:51:03  raasch
! Speed optimization by removing MINVAL/MAXVAL calls and by handling
! the "abs" case in a different way than the min/max cases,
! translation of remaining variables
!
! Revision 1.7  2002/06/11 13:08:16  raasch
! Last change limited to IBM since it does not work on 64-bit machines
!
! Revision 1.6  2002/05/02  18:50:36  18:50:36  raasch (Siegfried Raasch)
! Type of fmax, fmax_l, fmin and fmin_l changed to REAL (KIND=4).
! 
! Revision 1.5  2001/01/22 06:51:02  raasch
! Module test_variables removed
!
! Revision 1.4  2000/12/20 12:19:57  letzel
! All comments translated into English.
!
! Revision 1.3  1998/07/06 12:14:37  raasch
! + USE test_variables
!
! Revision 1.2  1997/08/11 06:16:54  raasch
! Indices des ermittelten Minumums/Maximums werden an PEs gesendet
!
! Revision 1.1  1997/07/24 11:14:03  raasch
! Initial revision
!
!
! Description:
! ------------
! Determine the array minimum/maximum and the corresponding indices.
!-------------------------------------------------------------------------------!

    USE indices
    USE pegrid

    IMPLICIT NONE

    CHARACTER (LEN=*) ::  mode

    INTEGER           ::  i, i1, i2, id_fmax, id_fmin, j, j1, j2, k, k1, k2, &
                          fmax_ijk(3), fmax_ijk_l(3), fmin_ijk(3), &
                          fmin_ijk_l(3), value_ijk(3)
    INTEGER, OPTIONAL ::  value1_ijk(3)
    REAL              ::  value, &
                          ar(i1:i2,j1:j2,k1:k2)
#if defined( __ibm )
    REAL (KIND=4)     ::  fmax(2), fmax_l(2), fmin(2), fmin_l(2)  ! on 32bit-
                          ! machines MPI_2REAL must not be replaced by
                          ! MPI_2DOUBLE_PRECISION
#else
    REAL              ::  fmax(2), fmax_l(2), fmin(2), fmin_l(2)
#endif
    REAL, OPTIONAL    ::  value1


!
!-- Determine array minimum
    IF ( mode == 'min'  .OR.  mode == 'minmax' )  THEN

!
!--    Determine the local minimum
       fmin_ijk_l = MINLOC( ar )
       fmin_ijk_l(1) = i1 + fmin_ijk_l(1) - 1    ! MINLOC assumes lowerbound = 1
       fmin_ijk_l(2) = j1 + fmin_ijk_l(2) - 1
       fmin_ijk_l(3) = k1 + fmin_ijk_l(3) - 1
       fmin_l(1)  = ar(fmin_ijk_l(1),fmin_ijk_l(2),fmin_ijk_l(3))

#if defined( __parallel )
       fmin_l(2)  = myid
       CALL MPI_ALLREDUCE( fmin_l, fmin, 1, MPI_2REAL, MPI_MINLOC, comm2d, ierr )

!
!--    Determine the global minimum. Result stored on PE0.
       id_fmin = fmin(2)
       IF ( id_fmin /= 0 )  THEN
          IF ( myid == 0 )  THEN
             CALL MPI_RECV( fmin_ijk, 3, MPI_INTEGER, id_fmin, 0, comm2d, &
                            status, ierr )
          ELSEIF ( myid == id_fmin )  THEN
             CALL MPI_SEND( fmin_ijk_l, 3, MPI_INTEGER, 0, 0, comm2d, ierr )
          ENDIF
       ELSE
          fmin_ijk = fmin_ijk_l
       ENDIF
!
!--    Send the indices of the just determined array minimum to other PEs
       CALL MPI_BCAST( fmin_ijk, 3, MPI_INTEGER, 0, comm2d, ierr )
#else
       fmin(1)  = fmin_l(1)
       fmin_ijk = fmin_ijk_l
#endif

    ENDIF

!
!-- Determine array maximum
    IF ( mode == 'max'  .OR.  mode == 'minmax' )  THEN

!
!--    Determine the local maximum
       fmax_ijk_l = MAXLOC( ar )
       fmax_ijk_l(1) = i1 + fmax_ijk_l(1) - 1    ! MAXLOC assumes lowerbound = 1
       fmax_ijk_l(2) = j1 + fmax_ijk_l(2) - 1
       fmax_ijk_l(3) = k1 + fmax_ijk_l(3) - 1
       fmax_l(1) = ar(fmax_ijk_l(1),fmax_ijk_l(2),fmax_ijk_l(3))

#if defined( __parallel )
       fmax_l(2)  = myid
       CALL MPI_ALLREDUCE( fmax_l, fmax, 1, MPI_2REAL, MPI_MAXLOC, comm2d, ierr )

!
!--    Determine the global maximum. Result stored on PE0.
       id_fmax = fmax(2)
       IF ( id_fmax /= 0 )  THEN
          IF ( myid == 0 )  THEN
             CALL MPI_RECV( fmax_ijk, 3, MPI_INTEGER, id_fmax, 0, comm2d, &
                            status, ierr )
          ELSEIF ( myid == id_fmax )  THEN
             CALL MPI_SEND( fmax_ijk_l, 3, MPI_INTEGER, 0, 0, comm2d, ierr )
          ENDIF
       ELSE
          fmax_ijk = fmax_ijk_l
       ENDIF
!
!--    send the indices of the just determined array maximum to other PEs
       CALL MPI_BCAST( fmax_ijk, 3, MPI_INTEGER, 0, comm2d, ierr )
#else
       fmax(1)  = fmax_l(1)
       fmax_ijk = fmax_ijk_l
#endif

    ENDIF

!
!-- Determine absolute array maximum
    IF ( mode == 'abs' )  THEN

!
!--    Determine the local absolut maximum
       fmax_l(1)     = 0.0
       fmax_ijk_l(1) =  i1
       fmax_ijk_l(2) =  j1
       fmax_ijk_l(3) =  k1
       DO  k = k1, k2
          DO  j = j1, j2
             DO  i = i1, i2
                IF ( ABS( ar(i,j,k) ) > fmax_l(1) )  THEN
                   fmax_l(1) = ABS( ar(i,j,k) )
                   fmax_ijk_l(1) = i
                   fmax_ijk_l(2) = j
                   fmax_ijk_l(3) = k
                ENDIF
             ENDDO
          ENDDO
       ENDDO

!
!--    Set a flag in case that the determined value is negative.
!--    A constant offset has to be subtracted in order to handle the special
!--    case i=0 correctly
       IF ( ar(fmax_ijk_l(1),fmax_ijk_l(2),fmax_ijk_l(3)) < 0.0 )  THEN
          fmax_ijk_l(1) = -fmax_ijk_l(1) - 10
       ENDIF

#if defined( __parallel )
       fmax_l(2)  = myid
       CALL MPI_ALLREDUCE( fmax_l, fmax, 1, MPI_2REAL, MPI_MAXLOC, comm2d, &
                           ierr )

!
!--    Determine the global absolut maximum. Result stored on PE0.
       id_fmax = fmax(2)
       IF ( id_fmax /= 0 )  THEN
          IF ( myid == 0 )  THEN
             CALL MPI_RECV( fmax_ijk, 3, MPI_INTEGER, id_fmax, 0, comm2d, &
                            status, ierr )
          ELSEIF ( myid == id_fmax )  THEN
             CALL MPI_SEND( fmax_ijk_l, 3, MPI_INTEGER, 0, 0, comm2d, ierr )
          ENDIF
       ELSE
          fmax_ijk = fmax_ijk_l
       ENDIF
!
!--    Send the indices of the just determined absolut maximum to other PEs
       CALL MPI_BCAST( fmax_ijk, 3, MPI_INTEGER, 0, comm2d, ierr )
#else
       fmax(1)  = fmax_l(1)
       fmax_ijk = fmax_ijk_l
#endif

    ENDIF

!
!-- Determine output parameters
    SELECT CASE( mode )

       CASE( 'min' )

          value     = fmin(1)
          value_ijk = fmin_ijk

       CASE( 'max' )

          value     = fmax(1)
          value_ijk = fmax_ijk

       CASE( 'minmax' )

          value      = fmin(1)
          value_ijk  = fmin_ijk
          value1     = fmax(1)
          value1_ijk = fmax_ijk

       CASE( 'abs' )

          value     = fmax(1)
          value_ijk = fmax_ijk
          IF ( fmax_ijk(1) < 0 )  THEN
             value        = -value
             value_ijk(1) = -value_ijk(1) - 10
          ENDIF

    END SELECT

!
!-- Limit index values to the range 0..nx, 0..ny
    IF ( value_ijk(3) ==   -1 )  value_ijk(3) = nx
    IF ( value_ijk(3) == nx+1 )  value_ijk(3) =  0
    IF ( value_ijk(2) ==   -1 )  value_ijk(2) = ny
    IF ( value_ijk(2) == ny+1 )  value_ijk(2) =  0


 END SUBROUTINE global_min_max