#if defined(NOMPIR8) /* LAM does not support mpi_real[48] */
# define MTYPE4 mpi_real
#else /* most MPI's allow mpi_real[48] */
# define MTYPE4 mpi_real4
#endif

!
!-----------------------------------------------------------------------
!
!     machine dependent I/O routines.
!     MPI-2 I/O version, with I/O from first processor in each row.
!     contained in module mod_za.
!
!     author:  Alan J. Wallcraft,  NRL.
!
!-----------------------------------------------------------------------
!
      subroutine zagetc(cline,ios, iunit)
      implicit none
!
      character*80, intent(out)   :: cline
      integer,      intent(out)   :: ios
      integer,      intent(in)    :: iunit
!
!**********
!*
!  1) machine specific routine for reading one text line from a file.
!
!  2) The read is performed on the first processor only.
!*
!**********
!
      integer        iline,ibuf
      common/czgetc/ iline(81,0:1),ibuf
      save  /czgetc/
!
      integer i
!
! --- I/O from first processor only
!
      ibuf = mod(ibuf+1,2)  !initialized in zaiost
!
      if     (mnproc.eq.1) then
        read(iunit,'(a)',iostat=ios) cline
        do i= 1,80
          iline(i,ibuf) = ichar(cline(i:i))
        enddo
        iline(81,ibuf) = ios
      endif
!
!     broadcast to all other processors
!
      call xcgetc(iline(:,ibuf))
      do i= 1,80
        cline(i:i) = char(iline(i,ibuf))
      enddo
      ios = iline(81,ibuf)  ! iostat value
      return
      end subroutine zagetc

      subroutine zaiopn(cstat, iaunit)
      implicit none
!
      integer,       intent(in)    :: iaunit
      character*(*), intent(in)    :: cstat
!
      integer        iarec
      common/czioxx/ iarec(999)
      save  /czioxx/
      integer        iahand
      common/cziox2/ iahand(999)
      save  /cziox2/
!
!**********
!*
!  1) machine specific routine for opening a file for array i/o.
!
!     must call zaiost before first call to zaiopn.
!     see also 'zaiope' and 'zaiopf'.
!
!  2) the filename is taken from the environment variable FORxxxA,
!       where xxx = iaunit, with default fort.xxxa.
!
!     array i/o is mpi-2 i/o.
!
!  3) iaunit+uaoff is the i/o unit used for arrays.  array i/o might not
!      use fortran i/o units, but, for compatability, assume that
!      iaunit+uaoff refers to a fortran i/o unit anyway.
!     cstat indicates the file type, it can be 'scratch', 'old', or
!      'new'.
!     all i/o to iaunit must be performed by zaiord and zaiowr.
!     the file should be closed using zaiocl.
!*
!**********
!
! --- spval  = data void marker, 2^100 or about 1.2676506e30
      real*4     spval
      parameter (spval=2.0**100)
!
      include 'mpif.h'
      integer        mpierr,mpireq,mpistat
      common/xcmpii/ mpierr,mpireq(4), &
                     mpistat(mpi_status_size,4*iqr)
      save  /xcmpii/
!
      integer(kind=mpi_offset_kind) disp
      integer                       iamode,iahint
      character                     cfile*256,cenv*7
#if defined(TIMER)
!
      call xctmr0(16)
#endif
!
!     test file state.
!
      if     (iarec(iaunit).ne.-1) then
        write(lp,9000) iaunit
        call xcstop('(zaiopn)')
               stop '(zaiopn)'
      endif
!
      iarec(iaunit) = 0
!
! --- I/O from first processor in each row.
!
      if     (mproc.eq.mp_1st) then
!
!     if     (mnproc.eq.1) then
!     write(lp,*) 'zaiopn - iaunit = ',iaunit
!     call flush(lp)
!     endif
!
!     get filename.
!
      write(cenv,"('FOR',i3.3,'A')") iaunit
      cfile = ' '
      call getenv(cenv,cfile)
      if     (cfile.eq.' ') then
        write(cfile,"('fort.',i3.3,'a')") iaunit
      endif
!
!     open file.
!
      if     (cstat.eq.'OLD' .or. &
              cstat.eq.'old'     ) then
        iamode = MPI_MODE_RDONLY + &
                 MPI_MODE_UNIQUE_OPEN
        iahint = file_info_zaiord  !see zaiost
        file_count_zaiord = file_count_zaiord + 1
      elseif (cstat.eq.'NEW' .or. &
              cstat.eq.'new'     ) then
        iamode = MPI_MODE_WRONLY + &
                 MPI_MODE_CREATE + &
                 MPI_MODE_EXCL   + &
                 MPI_MODE_UNIQUE_OPEN
        iahint = file_info_zaiowr  !see zaiost
        file_count_zaiowr = file_count_zaiowr + 1
      else !scratch file
        iamode = MPI_MODE_RDWR            + &
                 MPI_MODE_DELETE_ON_CLOSE + &
                 MPI_MODE_UNIQUE_OPEN
        iahint = file_info_zaiowr  !see zaiost
        file_count_zaiowr = file_count_zaiowr + 1
      endif
      call mpi_file_open(group_1st_in_row, &
                         trim(cfile), &
                         iamode, &
                         iahint, &
                         iahand(iaunit), &
                         mpierr)
      if     (mpierr.ne.0) then
        write(lp,9100) iaunit
        write(lp,*) 'mpi_file_open - mpierr = ',mpierr
        call flush(lp)
        call xchalt('(zaiopn)')
               stop '(zaiopn)'
      endif !mpierr
      disp = 0
      call mpi_file_set_view(iahand(iaunit), &
                             disp, &
                             MTYPE4, &
                             MTYPE4, &
                             "native",   & !1st convert to big-endian if necessary
                             iahint, &
                             mpierr)
      if     (mpierr.ne.0) then
        write(lp,9100) iaunit
        write(lp,*) 'mpi_file_set_view - mpierr = ',mpierr
        call flush(lp)
        call xchalt('(zaiopn)')
               stop '(zaiopn)'
      endif !mpierr
!
      endif  ! I/O from first processor in each row
      call xcsync(no_flush)
#if defined(TIMER)
!
      call xctmr1(16)
#endif
      return
!
 9000 format(/ /10x,'error in zaiopn -  array I/O unit ', &
         i3,' is not marked as available.'/ /)
 9100 format(/ /10x,'error in zaiopn -  can''t open unit ',i3, &
         ', for array I/O.'/ /)
      end subroutine zaiopn

      subroutine zaiope(cenv,cstat, iaunit)
      implicit none
!
      integer,       intent(in)    :: iaunit
      character*(*), intent(in)    :: cenv,cstat
!
      integer        iarec
      common/czioxx/ iarec(999)
      save  /czioxx/
      integer        iahand
      common/cziox2/ iahand(999)
      save  /cziox2/
!
!**********
!*
!  1) machine specific routine for opening a file for array i/o.
!
!     must call zaiost before first call to zaiope.
!     see also 'zaiopn' and 'zaiopf'.
!
!  2) the filename is taken from environment variable 'cenv'.
!
!     array i/o is mpi-2 i/o.
!
!  3) iaunit+uaoff is the i/o unit used for arrays.  array i/o might not
!      use fortran i/o units, but, for compatability, assume that
!      iaunit+uaoff refers to a fortran i/o unit anyway.
!     cstat indicates the file type, it can be 'scratch', 'old', or
!      'new'.
!     all i/o to iaunit must be performed by zaiord and zaiowr.
!      arrays passed to these routines must conform to 'h'.
!     the file should be closed using zaiocl.
!*
!**********
!
! --- spval  = data void marker, 2^100 or about 1.2676506e30
      real*4     spval
      parameter (spval=2.0**100)
!
      include 'mpif.h'
      integer        mpierr,mpireq,mpistat
      common/xcmpii/ mpierr,mpireq(4), &
                     mpistat(mpi_status_size,4*iqr)
      save  /xcmpii/
!
      integer(kind=mpi_offset_kind) disp
      integer                       iamode,iahint
      character                     cfile*256
!
#if defined(TIMER)
!
      call xctmr0(16)
#endif
!
!     test file state.
!
      if     (iarec(iaunit).ne.-1) then
        write(lp,9000) iaunit
        call xcstop('(zaiope)')
               stop '(zaiope)'
      endif
!
      iarec(iaunit) = 0
!
! --- I/O from first processor in each row.
!
      if     (mproc.eq.mp_1st) then
!
!     if     (mnproc.eq.1) then
!     write(lp,*) 'zaiope - iaunit = ',iaunit
!     call flush(lp)
!     endif
!
!     get filename.
!
      cfile = ' '
      call getenv(cenv,cfile)
      if     (cfile.eq.' ') then
        write(lp,9300) trim(cenv)
        write(lp,*) 'iaunit = ',iaunit
        call flush(lp)
        call xchalt('(zaiope)')
               stop '(zaiope)'
      endif
!
!     open file.
!
      if     (cstat.eq.'OLD' .or. &
              cstat.eq.'old'     ) then
        iamode = MPI_MODE_RDONLY + &
                 MPI_MODE_UNIQUE_OPEN
        iahint = file_info_zaiord  !see zaiost
        file_count_zaiord = file_count_zaiord + 1
      elseif (cstat.eq.'NEW' .or. &
              cstat.eq.'new'     ) then
        iamode = MPI_MODE_WRONLY + &
                 MPI_MODE_CREATE + &
                 MPI_MODE_EXCL   + &
                 MPI_MODE_UNIQUE_OPEN
        iahint = file_info_zaiowr  !see zaiost
        file_count_zaiowr = file_count_zaiowr + 1
      else !scratch file
        iamode = MPI_MODE_RDWR            + &
                 MPI_MODE_DELETE_ON_CLOSE + &
                 MPI_MODE_UNIQUE_OPEN
        iahint = file_info_zaiowr  !see zaiost
        file_count_zaiowr = file_count_zaiowr + 1
      endif
      call mpi_file_open(group_1st_in_row, &
                         trim(cfile), &
                         iamode, &
                         iahint, &
                         iahand(iaunit), &
                         mpierr)
      if     (mpierr.ne.0) then
        write(lp,9100) iaunit,trim(cfile)
        write(lp,*) 'mpi_file_open - mpierr = ',mpierr
        write(lp,*) 'cenv = ',trim(cenv)
        call flush(lp)
        call xchalt('(zaiope)')
               stop '(zaiope)'
      endif !mpierr
      disp = 0
      call mpi_file_set_view(iahand(iaunit), &
                             disp, &
                             MTYPE4, &
                             MTYPE4, &
                             "native",   & !1st convert to big-endian if necessary
                             iahint, &
                             mpierr)
      if     (mpierr.ne.0) then
        write(lp,9100) iaunit,trim(cfile)
        write(lp,*) 'mpi_file_set_view - mpierr = ',mpierr
        write(lp,*) 'cenv = ',trim(cenv)
        call flush(lp)
        call xchalt('(zaiope)')
               stop '(zaiope)'
      endif !mpierr
!
      endif  ! I/O from first processor in each row
      call xcsync(no_flush)
#if defined(TIMER)
!
      call xctmr1(16)
#endif
      return
!
 9000 format(/ /10x,'error in zaiope -  array I/O unit ', &
         i3,' is not marked as available.'/ /)
 9100 format(/ /10x,'error in zaiope -  can''t open unit ',i3, &
         ', for array I/O.' / &
         10x,'cfile = ',a/ /)
 9300 format(/ /10x,'error in zaiope -  environment variable ',a, &
         ' not defined'/ /)
      end subroutine zaiope

      subroutine zaiopf(cfile,cstat, iaunit)
      implicit none
!
      integer,       intent(in)    :: iaunit
      character*(*), intent(in)    :: cfile,cstat
!
      integer        iarec
      common/czioxx/ iarec(999)
      save  /czioxx/
      integer        iahand
      common/cziox2/ iahand(999)
      save  /cziox2/
!
!**********
!*
!  1) machine specific routine for opening a file for array i/o.
!
!     must call zaiost before first call to zaiopf.
!     see also 'zaiopn' and 'zaiope'.
!
!  2) the filename is taken from 'cfile'.
!
!     array i/o is mpi-2 i/o.
!
!  3) iaunit+uaoff is the i/o unit used for arrays.  array i/o might not
!      use fortran i/o units, but, for compatability, assume that
!      iaunit+uaoff refers to a fortran i/o unit anyway.
!     cstat indicates the file type, it can be 'scratch', 'old', or
!      'new'.
!     all i/o to iaunit must be performed by zaiord and zaiowr.
!      arrays passed to these routines must conform to 'h'.
!     the file should be closed using zaiocl.
!*
!**********
!
! --- spval  = data void marker, 2^100 or about 1.2676506e30
      real*4     spval
      parameter (spval=2.0**100)
!
      include 'mpif.h'
      integer        mpierr,mpireq,mpistat
      common/xcmpii/ mpierr,mpireq(4), &
                     mpistat(mpi_status_size,4*iqr)
      save  /xcmpii/
!
      integer(kind=mpi_offset_kind) disp
      integer                       iamode,iahint
      logical                       lphint
#if defined(TIMER)
!
      call xctmr0(16)
#endif
!
!     test file state.
!
      if     (iarec(iaunit).ne.-1) then
        write(lp,9000) iaunit
        call xcstop('(zaiopf)')
               stop '(zaiopf)'
      endif
!
      iarec(iaunit) = 0
!
! --- I/O from first processor in each row.
!
      if     (mproc.eq.mp_1st) then
!
!     if     (mnproc.eq.1) then
!     write(lp,*) 'zaiopf - iaunit = ',iaunit
!     call flush(lp)
!     endif
!
!     open file.
!
      if     (cstat.eq.'OLD' .or. &
              cstat.eq.'old'     ) then
        iamode = MPI_MODE_RDONLY + &
                 MPI_MODE_UNIQUE_OPEN
        iahint = file_info_zaiord  !see zaiost
        file_count_zaiord = file_count_zaiord + 1
        lphint = file_count_zaiord .eq. 1
      elseif (cstat.eq.'NEW' .or. &
              cstat.eq.'new'     ) then
        iamode = MPI_MODE_WRONLY + &
                 MPI_MODE_CREATE + &
                 MPI_MODE_EXCL   + &
                 MPI_MODE_UNIQUE_OPEN
        iahint = file_info_zaiowr  !see zaiost
        file_count_zaiowr = file_count_zaiowr + 1
        lphint = file_count_zaiowr .eq. 1
      else !scratch file
        iamode = MPI_MODE_RDWR            + &
                 MPI_MODE_DELETE_ON_CLOSE + &
                 MPI_MODE_UNIQUE_OPEN
        iahint = file_info_zaiowr  !see zaiost
        file_count_zaiowr = file_count_zaiowr + 1
        lphint = .true.
      endif
      call mpi_file_open(group_1st_in_row, &
                         trim(cfile), &
                         iamode, &
                         iahint, &
                         iahand(iaunit), &
                         mpierr)
      if     (mpierr.ne.0) then
        write(lp,9100) iaunit,trim(cfile)
        write(lp,*) 'mpi_file_open - mpierr = ',mpierr
        call flush(lp)
        call xchalt('(zaiopf)')
               stop '(zaiopf)'
      endif !mpierr
      disp = 0
      call mpi_file_set_view(iahand(iaunit), &
                             disp, &
                             MTYPE4, &
                             MTYPE4, &
                             "native",   & !1st convert to big-endian if necessary
                             iahint, &
                             mpierr)
      if     (mpierr.ne.0) then
        write(lp,9100) iaunit,trim(cfile)
        write(lp,*) 'mpi_file_set_view - mpierr = ',mpierr
        call flush(lp)
        call xchalt('(zaiopf)')
               stop '(zaiopf)'
      endif !mpierr
      if     (lphint .and. mnproc.eq.1) then
        call zaio_hints(iahand(iaunit))
      endif
!
      endif  ! I/O from first processor in each row
      call xcsync(no_flush)
#if defined(TIMER)
!
      call xctmr1(16)
#endif
      return
!
 9000 format(/ /10x,'error in zaiopf -  array I/O unit ', &
         i3,' is not marked as available.'/ /)
 9100 format(/ /10x,'error in zaiopf -  can''t open unit ',i3, &
         ', for array I/O.' / &
         10x,'cfile = ',a/ /)
      end subroutine zaiopf

#if defined(HPEI)
      subroutine zaio_hints(file_handle)
      implicit none
!
      integer, intent(in) :: file_handle
!
!**********
!*
!  1) prints current hints.
!
!  2) dummy version for HPE with Intel MPI via mpt perfboost
!*
!**********
!
      write(6,"(/a)") 'zaio_hints:'
      write(6,"(/a)") '    SKIPPED'
      write(6,*)
      return
      end subroutine zaio_hints
#else
      subroutine zaio_hints(file_handle)
      implicit none
!
      integer, intent(in) :: file_handle
!
!**********
!*
!  1) prints current hints.
!*
!**********
!
      include 'mpif.h'
!
      character(mpi_max_info_key) key
      character(mpi_max_info_val) value
!
      logical flag
      integer hints,i,mpierr,nkeys
!
      call MPI_File_get_info(file_handle, hints, mpierr)
      call MPI_Info_get_nkeys(hints, nkeys, mpierr)
!
      write(6,"(/a)") 'zaio_hints:'
      do i= 0,nkeys-1
        call MPI_Info_get_nthkey(hints, i, key, mpierr)
        call MPI_Info_get(hints, key, &
                          mpi_max_info_val, value, flag, mpierr)
        write(6,"(4a)") &
          '    key=',trim(key), &
          '  value=',trim(value)
      enddo
      write(6,*)
      return
      end subroutine zaio_hints
#endif

      subroutine zaiopi(lopen, iaunit)
      implicit none
!
      logical, intent(out)   :: lopen
      integer, intent(in)    :: iaunit
!
      integer        iarec
      common/czioxx/ iarec(999)
      save  /czioxx/
      integer        iahand
      common/cziox2/ iahand(999)
      save  /cziox2/
!
!**********
!*
!  1) is an array i/o unit open?
!
!  2) must call zaiost before first call to zaiopi.
!*
!**********
!
      lopen = iarec(iaunit).ne.-1
      return
      end subroutine zaiopi

      subroutine zaiost
      implicit none
!
      integer        iarec
      common/czioxx/ iarec(999)
      save  /czioxx/
      integer        iahand
      common/cziox2/ iahand(999)
      save  /cziox2/
!
!**********
!*
!  1) machine specific routine for initializing array i/o.
!
!  2) see also zaiopn, zaiord, zaiowr, and zaiocl.
!*
!**********
!
      include 'mpif.h'
      integer        mpierr,mpireq,mpistat
      common/xcmpii/ mpierr,mpireq(4), &
                     mpistat(mpi_status_size,4*iqr)
      save  /xcmpii/
!
      integer        iline,ibuf
      common/czgetc/ iline(81,0:1),ibuf
      save  /czgetc/
!
      integer       i
      character(mpi_max_info_val) value
!
!     mpi-2 hints for array i/o
!
      file_count_zaiord = 0
      file_count_zaiowr = 0
      call mpi_info_create(file_info_zaiord, &
                           mpierr)
      call mpi_info_create(file_info_zaiowr, &
                           mpierr)
#if defined(AIX)
      call mpi_info_set(file_info_zaiord, &
                        'IBM_largeblock_io',   & !read on calling task
                        'true', &
                        mpierr)
      write(value,'(i10)') (((itdm*jtdm+4095)/4096)*4096)*4
      call mpi_info_set(file_info_zaiowr, &
                        'IBM_io_buffer_size', &
                        trim(value),           & !write from a single task
                        mpierr)
#else
      call mpi_info_free(file_info_zaiord,   & !set to mpi_info_null
                         mpierr)
      call mpi_info_free(file_info_zaiowr,   & !set to mpi_info_null
                         mpierr)
#endif
!
      if     (mnproc.eq.1) then
        write(lp,'(/a/)') &
          'zaiost - Array I/O is MPI-2 I/O from one task per row'
      endif
!
      do i= 1,999
        iarec(i) = -1
      enddo
!
      ibuf = 0
#if defined(RELO)
!
! --- n2drec = size of output 2-d array, multiple of 4096
      n2drec = ((itdm*jtdm+4095)/4096)*4096
!
      allocate( wminy(jdm),wmaxy(jdm),htmp(idm*jdm) )
      call mem_stat_add( (2*jdm+idm*jdm)/2 ) !real*4, so /2
!
      if     (mproc.eq.mp_1st) then
        if     (nproc.ne.jpr) then
          allocate( w(itdm*jj) )
          call mem_stat_add( (itdm*jj)/2 ) !real*4, so /2
        else
          allocate( w(itdm*jj+n2drec-itdm*jtdm) )
          call mem_stat_add( (itdm*jj+n2drec-itdm*jtdm)/2 ) !real*4, so /2
        endif
      else
        allocate( w(1) )
      endif
#else
      if     (mproc.eq.mp_1st) then
        if     (nproc.ne.jpr) then
          allocate( w(itdm*jj) )
        else
          allocate( w(itdm*jj+n2drec-itdm*jtdm) )
        endif
      else
        allocate( w(1) )
      endif
#endif
#if defined(TIMER)
!
!     initialize timers.
!
      call xctmrn(16,'zaio**')
      call xctmrn(17,'zaiord')
      call xctmrn(18,'zaiowr')
#endif
      return
      end subroutine zaiost

      subroutine zaiocl(iaunit)
      implicit none
!
      integer, intent(in)    :: iaunit
!
      integer        iarec
      common/czioxx/ iarec(999)
      save  /czioxx/
      integer        iahand
      common/cziox2/ iahand(999)
      save  /cziox2/
!
!**********
!*
!  1) machine specific routine for array i/o file closing.
!
!     must call zaiopn for this array unit before calling zaiocl.
!
!  2) array i/o is mpi-2 i/o.
!*
!**********
!
      include 'mpif.h'
      integer        mpierr,mpireq,mpistat
      common/xcmpii/ mpierr,mpireq(4), &
                     mpistat(mpi_status_size,4*iqr)
      save  /xcmpii/
#if defined(TIMER)
!
      call xctmr0(16)
#endif
!
      if     (iarec(iaunit).lt.0) then
        write(lp,9000) iaunit
        call xcstop('(zaiocl)')
               stop '(zaiocl)'
      endif
!
      iarec(iaunit) = -1
!
! --- I/O from first processor in each row
!
      if     (mproc.eq.mp_1st) then
!
!     if     (mnproc.eq.1) then
!     write(lp,*) 'zaiocl - iaunit = ',iaunit
!     call flush(lp)
!     endif
!
      call mpi_file_close(iahand(iaunit),mpierr)
!
      endif  ! I/O from first processor in each row
      call xcsync(no_flush)
#if defined(TIMER)
!
      call xctmr1(16)
#endif
      return
!
 9000 format(/ /10x,'error in zaiocl -  array I/O unit ', &
         i3,' is not marked as open.'/ /)
      end subroutine zaiocl

      subroutine zaiofl(iaunit)
      implicit none
!
      integer, intent(in)    :: iaunit
!
      integer        iarec
      common/czioxx/ iarec(999)
      save  /czioxx/
      integer        iahand
      common/cziox2/ iahand(999)
      save  /cziox2/
!
!**********
!*
!  1) machine specific routine for array i/o buffer flushing.
!
!     must call zaiopn for this array unit before calling zaiocl.
!
!  2) array i/o is mpi-2 i/o.
!*
!**********
!
      include 'mpif.h'
      integer        mpierr,mpireq,mpistat
      common/xcmpii/ mpierr,mpireq(4), &
                     mpistat(mpi_status_size,4*iqr)
      save  /xcmpii/
#if defined(TIMER)
!
      call xctmr0(16)
#endif
!
      if     (iarec(iaunit).lt.0) then
        write(lp,9000) iaunit
        call xcstop('(zaiofl)')
               stop '(zaiofl)'
      endif
!
! --- I/O from first processor in each row
!
      if     (mproc.eq.mp_1st) then
        call mpi_file_sync(iahand(iaunit),mpierr)
      endif  ! I/O from first processor in each row
      call xcsync(no_flush)
#if defined(TIMER)
!
      call xctmr1(16)
#endif
      return
!
 9000 format(/ /10x,'error in zaiofl -  array I/O unit ', &
         i3,' is not marked as open.'/ /)
      end subroutine zaiofl

      subroutine zaioiq(iaunit, irec)
      implicit none
!
      integer, intent(in)    :: iaunit
      integer, intent(out)   :: irec
!
      integer        iarec
      common/czioxx/ iarec(999)
      save  /czioxx/
      integer        iahand
      common/cziox2/ iahand(999)
      save  /cziox2/
!
!**********
!*
!  1) machine specific routine for array i/o inquiry.
!
!  2) returns the number of records processed, or -1 for a closed file.
!*
!**********
!
      irec = iarec(iaunit)
      return
      end subroutine zaioiq

      subroutine zaiorw(iaunit)
      implicit none
!
      integer, intent(in)    :: iaunit
!
      integer        iarec
      common/czioxx/ iarec(999)
      save  /czioxx/
      integer        iahand
      common/cziox2/ iahand(999)
      save  /cziox2/
!
!**********
!*
!  1) machine specific routine for array i/o file rewinding.
!
!     must call zaiopn for this array unit before calling zaiocl.
!
!  2) array i/o is mpi-2 i/o.
!*
!**********
#if defined(TIMER)
!
      call xctmr0(16)
#endif
!
      if     (iarec(iaunit).lt.0) then
        write(lp,9000) iaunit
        call xcstop('(zaiorw)')
               stop '(zaiorw)'
      endif
!
      iarec(iaunit) = 0
!
!     if     (mnproc.eq.1) then
!     write(lp,*) 'zaiorw - iaunit,rec = ',iaunit,iarec(iaunit)
!     call flush(lp)
!     endif
      call xcsync(no_flush)
#if defined(TIMER)
!
      call xctmr1(16)
#endif
      return
!
 9000 format(/ /10x,'error in zaiorw -  array I/O unit ', &
         i3,' is not marked as open.'/ /)
      end subroutine zaiorw

      subroutine zaiord3(h, l, mask,lmask, hmin,hmax,  iaunit)
      implicit none
!
      logical, intent(in)    :: lmask
      integer, intent(in)    :: l,iaunit
      integer, dimension (1-nbdy:idm+nbdy,1-nbdy:jdm+nbdy), &
               intent(in)    :: mask
#if defined(REAL4)
      real*4,  intent(out)   :: hmin(l),hmax(l)
      real*4,  dimension (1-nbdy:idm+nbdy,1-nbdy:jdm+nbdy,l), &
               intent(out)   :: h
#else
      real,    intent(out)   :: hmin(l),hmax(l)
      real,    dimension (1-nbdy:idm+nbdy,1-nbdy:jdm+nbdy,l), &
               intent(out)   :: h
#endif
!
!**********
!*
!  1) machine specific routine for 3-d array reading.
!
!     must call zaiopn for this array unit before calling zaiord.
!
!  2) array i/o is mpi-2 i/o.
!
!  3) iaunit+uaoff is the i/o unit used for arrays.  array i/o might not
!      use fortran i/o units, but, for compatability, assume that
!      iaunit+uaoff refers to a fortran i/o unit anyway.
!     the array, 'h',  must conform to that passed in the associated
!      call to zaiopn.
!
!  4) hmin,hmax are returned as the minimum and maximum value in the
!     array, ignoring array elements set to 2.0**100.
!     if lmask==.true. the range is calculated only where mask.ne.0,
!     with all other values unchanged in h on exit.  It is then an
!     error if mask.ne.0 anywhere the input is 2.0**100.
!*
!**********
!
!     this version just calls zaiord l times.
!
      integer k
!
      do k= 1,l
        call zaiord(h(1-nbdy,1-nbdy,k), mask,lmask, &
                    hmin(k),hmax(k), iaunit)
      enddo
!
      return
      end subroutine zaiord3

      subroutine zaiord(h, mask,lmask, hmin,hmax,  iaunit)
      implicit none
!
      logical, intent(in)    :: lmask
      integer, intent(in)    :: iaunit
      integer, dimension (1-nbdy:idm+nbdy,1-nbdy:jdm+nbdy), &
               intent(in)    :: mask
#if defined(REAL4)
      real*4,  intent(out)   :: hmin,hmax
      real*4,  dimension (1-nbdy:idm+nbdy,1-nbdy:jdm+nbdy), &
               intent(out)   :: h
#else
      real,    intent(out)   :: hmin,hmax
      real,    dimension (1-nbdy:idm+nbdy,1-nbdy:jdm+nbdy), &
               intent(out)   :: h
#endif
!
      integer        iarec
      common/czioxx/ iarec(999)
      save  /czioxx/
      integer        iahand
      common/cziox2/ iahand(999)
      save  /cziox2/
!
!**********
!*
!  1) machine specific routine for array reading.
!
!     must call zaiopn for this array unit before calling zaiord.
!
!  2) array i/o is mpi-2 i/o.
!
!  3) iaunit+uaoff is the i/o unit used for arrays.  array i/o might not
!      use fortran i/o units, but, for compatability, assume that
!      iaunit+uaoff refers to a fortran i/o unit anyway.
!     the array, 'h',  must conform to that passed in the associated
!      call to zaiopn.
!
!  4) hmin,hmax are returned as the minimum and maximum value in the
!     array, ignoring array elements set to 2.0**100.
!     if lmask==.true. the range is calculated only where mask.ne.0,
!     with all other values unchanged in h on exit.  It is then an
!     error if mask.ne.0 anywhere the input is 2.0**100.
!*
!**********
!
! --- spval  = data void marker, 2^100 or about 1.2676506e30
! --- n2drec = size of output 2-d array, multiple of 4096
      real*4     spval
      parameter (spval=2.0**100)
!
      include 'mpif.h'
      integer        mpierr,mpireq,mpistat
      common/xcmpii/ mpierr,mpireq(4), &
                     mpistat(mpi_status_size,4*iqr)
      save  /xcmpii/
!
      integer(kind=mpi_offset_kind) disp
      integer                        i,j
      real*4                         wmin,wmax
      real                           rmin(1),rmax(1)
#if defined(TIMER)
!
      call xctmr0(17)
#endif
!
      if     (iarec(iaunit).lt.0) then
        write(lp,9000) iaunit
        call xcstop('(zaiord)')
               stop '(zaiord)'
      endif
!
      iarec(iaunit) = iarec(iaunit) + 1
!
      wmin =  spval
      wmax = -spval
!
! --- I/O from first processor in each row
!
      if     (mproc.eq.mp_1st) then
!
!     if     (mnproc.eq.1) then
!     write(lp,*) 'zaiord - iaunit,rec = ',iaunit,iarec(iaunit)
!     write(lp,*) 'zaiord - mask.1,1    = ',amsk(1,1)
!     write(lp,*) 'zaiord - h.1,1       = ',atmp(1,1)
!     call flush(lp)
!     endif
!
      disp = n2drec
      disp = (iarec(iaunit)-1)*disp + itdm*j0
      call mpi_file_read_at(iahand(iaunit), &
                            disp, &
                            w(1), &
                            itdm*jj, &
                            MTYPE4, &
                            mpistat(1,1), &
                            mpierr)
      if     (mpierr.ne.0) then
        write(lp,9100) iarec(iaunit),iaunit
        write(lp,*) 'mpierr = ',mpierr
        call flush(lp)
        call xchalt('(zaiord)')
               stop '(zaiord)'
      endif !mpierr
      if     (.not.lmask) then
!       Get min and max of input array section.
!       must be done here because tiles need not cover the full domain.
!$OMP   PARALLEL DO PRIVATE(j,i) &
!$OMP            SCHEDULE(STATIC,jblk)
        do j= 1,jj
#if defined(ENDIAN_IO)
          call zaio_endian(w(1+(j-1)*itdm),itdm)  !swap to big-endian
#endif
          wminy(j) =  spval
          wmaxy(j) = -spval
          do i= 1,itdm
            if     (w(i+(j-1)*itdm).ne.spval) then
              wminy(j) = min( wminy(j), w(i+(j-1)*itdm) )
              wmaxy(j) = max( wmaxy(j), w(i+(j-1)*itdm) )
            endif
          enddo !i
        enddo !j
        wmin = minval(wminy(1:jj))
        wmax = maxval(wmaxy(1:jj))
      endif !Not Lmask
!
      endif !I/O from first processor in each row
!
! --- put field from 1st in row to all tiles
      call xcaput4(w,htmp, -1)  !w cast to a 2-d array
!
! --- Each processor loads h from htmp (where mask = 1)
! --- Each processor does local min max if lmask is true
!
      if     (lmask) then
!$OMP   PARALLEL DO PRIVATE(j,i) &
!$OMP            SCHEDULE(STATIC,jblk)
        do j= 1,jj
#if defined(ENDIAN_IO)
          call zaio_endian(htmp(1+(j-1)*ii),ii)  !swap to big-endian
#endif
          wminy(j) =  spval
          wmaxy(j) = -spval
          do i= 1,ii
            if     (mask(i,j).ne.0) then
              h(i,j) =                  htmp(i+(j-1)*ii)
              wminy(j) = min( wminy(j), htmp(i+(j-1)*ii) )
              wmaxy(j) = max( wmaxy(j), htmp(i+(j-1)*ii) )
            endif
          enddo !i
        enddo !j
        wmin = minval(wminy(1:jj))
        wmax = maxval(wmaxy(1:jj))
      else
!$OMP   PARALLEL DO PRIVATE(j,i) &
!$OMP            SCHEDULE(STATIC,jblk)
        do j= 1,jj
          do i= 1,ii
            h(i,j) = htmp(i+(j-1)*ii)
          enddo !i
        enddo !j
      endif !lmask:else
!
! --- Min/Max broadcast/gather
!
      rmin(1) = wmin
      rmax(1) = wmax
      call xcminr(rmin)
      call xcmaxr(rmax)
      hmin = rmin(1)
      hmax = rmax(1)
!
      if     (lmask .and. hmax.eq.spval) then
        if     (mnproc.eq.1) then
        write(lp,9200) iarec(iaunit),iaunit
        call flush(lp)
!       cfile = ' '
!       inquire(unit=iaunit+uaoff,name=cfile)
!       write(lp,'(3a)') 'FILENAME="',trim(cfile),'"'
!       call flush(lp)
        endif !master
        call xcstop('(zaiord)')
               stop '(zaiord)'
      endif
#if defined(TIMER)
!
      call xctmr1(17)
#endif
      return
!
 9000 format(/ /10x,'error in zaiord -  array I/O unit ', &
         i3,' is not marked as open.'/ /)
 9100 format(/ /10x,'error in zaiord -  can''t read record', &
         i4,' on array I/O unit ',i3,'.'/ /)
 9200 format(/ /10x,'error in zaiord -  record', &
         i4,' on array I/O unit ',i3, &
         ' has 2.0**100 outside masked region.'/ /)
      end subroutine zaiord

      subroutine zaiordg(hh4, iaunit)
      implicit none
!
      integer, intent(in)    :: iaunit
      real*4,  dimension (itdm,jtdm), &
               intent(out)   :: hh4
!
      integer        iarec
      common/czioxx/ iarec(999)
      save  /czioxx/
      integer        iahand
      common/cziox2/ iahand(999)
      save  /cziox2/
!
!**********
!*
!  1) machine specific routine for array reading.
!     returns non-tiled real*4 array.
!
!     must call zaiopn for this array unit before calling zaiord.
!
!  2) array i/o is mpi-2 i/o.
!
!  3) iaunit+uaoff is the i/o unit used for arrays.  array i/o might not
!      use fortran i/o units, but, for compatability, assume that
!      iaunit+uaoff refers to a fortran i/o unit anyway.
!     the array, 'h',  must conform to that passed in the associated
!      call to zaiopn.
!*
!**********
!
! --- n2drec = size of output 2-d array, multiple of 4096
!
      include 'mpif.h'
      integer        mpierr,mpireq,mpistat
      common/xcmpii/ mpierr,mpireq(4), &
                     mpistat(mpi_status_size,4*iqr)
      save  /xcmpii/
!
      integer(kind=mpi_offset_kind) disp
      integer                        i,j
#if defined(TIMER)
!
      call xctmr0(17)
#endif
!
      if     (iarec(iaunit).lt.0) then
        write(lp,9000) iaunit
        call xcstop('(zaiordg)')
               stop '(zaiordg)'
      endif
!
      iarec(iaunit) = iarec(iaunit) + 1
!
! --- I/O from first processor in each row
!
      if     (mproc.eq.mp_1st) then
!
!     if     (mnproc.eq.1) then
!     write(lp,*) 'zaiordg - iaunit,rec = ',iaunit,iarec(iaunit)
!     write(lp,*) 'zaiordg - h.1,1       = ',atmp(1,1)
!     call flush(lp)
!     endif
!
      disp = n2drec
      disp = (iarec(iaunit)-1)*disp + itdm*j0
      call mpi_file_read_at(iahand(iaunit), &
                            disp, &
                            w(1), &
                            itdm*jj, &
                            MTYPE4, &
                            mpistat(1,1), &
                            mpierr)
      if     (mpierr.ne.0) then
        write(lp,9100) iarec(iaunit),iaunit
        write(lp,*) 'mpierr = ',mpierr
        call flush(lp)
        call xchalt('(zaiordg)')
               stop '(zaiordg)'
      endif !mpierr
#if defined(ENDIAN_IO)
      call zaio_endian(w,itdm*jj)  !swap to big-endian
#endif
!
      endif !I/O from first processor in each row
!
! --- put field from 1st in row to all tiles
      call xcgput4(w,hh4, -1)  !w cast to a 2-d array
#if defined(TIMER)
!
      call xctmr1(17)
#endif
      return
!
 9000 format(/ /10x,'error in zaiordg -  array I/O unit ', &
         i3,' is not marked as open.'/ /)
 9100 format(/ /10x,'error in zaiordg -  can''t read record', &
         i4,' on array I/O unit ',i3,'.'/ /)
      end subroutine zaiordg

      subroutine zaiosk(iaunit)
      implicit none
!
      integer, intent(in)    :: iaunit
!
      integer        iarec
      common/czioxx/ iarec(999)
      save  /czioxx/
      integer        iahand
      common/cziox2/ iahand(999)
      save  /cziox2/
!
!**********
!*
!  1) machine specific routine for skipping an array read.
!
!     must call zaiopn for this array unit before calling zaiosk.
!
!  2) array i/o is mpi-2 i/o.
!
!  3) iaunit+uaoff is the i/o unit used for arrays.  array i/o might not
!      use fortran i/o units, but, for compatability, assume that
!      iaunit+uaoff refers to a fortran i/o unit anyway.
!     the array, 'h',  must conform to that passed in the associated
!      call to zaiopn.
!*
!**********
#if defined(TIMER)
!
      call xctmr0(16)
#endif
!
      if     (iarec(iaunit).lt.0) then
        write(lp,9000) iaunit
        call xcstop('(zaiosk)')
               stop '(zaiosk)'
      endif
!
      iarec(iaunit) = iarec(iaunit) + 1
!
!     if     (mnproc.eq.1) then
!     write(lp,*) 'zaiosk - iaunit,rec = ',iaunit,iarec(iaunit)
!     call flush(lp)
!     endif
      call xcsync(no_flush)
#if defined(TIMER)
!
      call xctmr1(16)
#endif
      return
!
 9000 format(/ /10x,'error in zaiosk -  array I/O unit ', &
         i3,' is not marked as open.'/ /)
      end subroutine zaiosk

      subroutine zaiowr3(h, l, mask,lmask, hmin,hmax, iaunit, lreal4)
      implicit none
!
      logical, intent(in)    :: lmask,lreal4
      integer, intent(in)    :: l,iaunit
      integer, dimension (1-nbdy:idm+nbdy,1-nbdy:jdm+nbdy), &
               intent(in)    :: mask
#if defined(REAL4)
      real*4,  intent(out)   :: hmin(l),hmax(l)
      real*4,  dimension (1-nbdy:idm+nbdy,1-nbdy:jdm+nbdy,l), &
               intent(inout) :: h
#else
      real,    intent(out)   :: hmin(l),hmax(l)
      real,    dimension (1-nbdy:idm+nbdy,1-nbdy:jdm+nbdy,l), &
               intent(inout) :: h
#endif
!
!**********
!*
!  1) machine specific routine for 3-d array writing.
!
!     must call zaiopn for this array unit before calling zaiord.
!
!  2) array i/o is mpi-2 i/o.
!
!  3) iaunit+uaoff is the i/o unit used for arrays.  array i/o might not
!      use fortran i/o units, but, for compatability, assume that
!      iaunit+uaoff refers to a fortran i/o unit anyway.
!     the array, 'h',  must conform to that passed in the associated
!      call to zaiopn.
!
!  4) hmin,hmax are returned as the minimum and maximum value in the array.
!     if lmask==.true. the range is only where mask.ne.0, with all other
!     values output as 2.0**100.
!
!  5) If lreal4==.true. then h is overwritten on exit with real*4 version
!     of the same array.  This is typically used for reproducability on
!     restart.
!*
!**********
!
!     this version just calls zaiowr l times.
!
      integer k
!
      do k= 1,l
        call zaiowr(h(1-nbdy,1-nbdy,k), mask,lmask, &
                    hmin(k),hmax(k), iaunit, lreal4)
      enddo
      return
      end subroutine zaiowr3

      subroutine zaiowr(h, mask,lmask, hmin,hmax,  iaunit, lreal4)
      implicit none
!
      logical, intent(in)    :: lmask,lreal4
      integer, intent(in)    :: iaunit
      integer, dimension (1-nbdy:idm+nbdy,1-nbdy:jdm+nbdy), &
               intent(in)    :: mask
#if defined(REAL4)
      real*4,  intent(out)   :: hmin,hmax
      real*4,  dimension (1-nbdy:idm+nbdy,1-nbdy:jdm+nbdy), &
               intent(inout) :: h
#else
      real,    intent(out)   :: hmin,hmax
      real,    dimension (1-nbdy:idm+nbdy,1-nbdy:jdm+nbdy), &
               intent(inout) :: h
#endif
!
      integer        iarec
      common/czioxx/ iarec(999)
      save  /czioxx/
      integer        iahand
      common/cziox2/ iahand(999)
      save  /cziox2/
!
!**********
!*
!  1) machine specific routine for array writing.
!
!     must call zaiopn for this array unit before calling zaiord.
!
!  2) array i/o is mpi-2 i/o.
!
!  3) iaunit+uaoff is the i/o unit used for arrays.  array i/o might not
!      use fortran i/o units, but, for compatability, assume that
!      iaunit+uaoff refers to a fortran i/o unit anyway.
!     the array, 'h',  must conform to that passed in the associated
!      call to zaiopn.
!
!  4) hmin,hmax are returned as the minimum and maximum value in the array.
!     if lmask==.true. the range is only where mask.ne.0, with all other
!     values output as 2.0**100.
!
!  5) If lreal4==.true. then h is overwritten on exit with real*4 version
!     of the same array.  This is typically used for reproducability on
!     restart.
!*
!**********
!
! --- spval  = data void marker, 2^100 or about 1.2676506e30
! --- n2drec = size of output 2-d array, multiple of 4096
      real*4     spval
      parameter (spval=2.0**100)
!
      include 'mpif.h'
      integer        mpierr,mpireq,mpistat
      common/xcmpii/ mpierr,mpireq(4), &
                     mpistat(mpi_status_size,4*iqr)
      save  /xcmpii/
!
      integer(kind=mpi_offset_kind) disp
      integer                       i,j,lrec
      real                          rmin(1),rmax(1)
      real*4                        data_void(1),vsave4
#if defined(TIMER)
!
      call xctmr0(18)
#endif
!
      if     (iarec(iaunit).lt.0) then
        write(lp,9000) iaunit
        call xcstop('(zaiowr)')
               stop '(zaiowr)'
      endif
!
      iarec(iaunit) = iarec(iaunit) + 1
!
      data_void(1) = spval
#if defined(ENDIAN_IO)
      call zaio_endian(data_void,1) !swap to big-endian
#endif
!
! --- Copy into real*4 buffer, and find Min,Max
!
      if     (lreal4) then
        if     (lmask) then
!$OMP     PARALLEL DO PRIVATE(j,i) &
!$OMP              SCHEDULE(STATIC,jblk)
          do j= 1,jj
            wminy(j)= spval
            wmaxy(j)=-spval
            do i= 1,ii
              if     (mask(i,j).ne.0) then
                htmp(i+(j-1)*ii) = h(i,j)
                wminy(j)=min(wminy(j),htmp(i+(j-1)*ii))
                wmaxy(j)=max(wmaxy(j),htmp(i+(j-1)*ii))
              else
                htmp(i+(j-1)*ii) = spval
              endif
#if defined(REAL4)
! ---         h(i,j) = htmp(i+(j-1)*ii)  ! h is already real*4
#else
              h(i,j) = htmp(i+(j-1)*ii)  ! h is not real*4, so update it
#endif
            enddo !i
#if defined(ENDIAN_IO)
            call zaio_endian(htmp(1+(j-1)*ii),ii)  !swap to big-endian
#endif
          enddo !j
        else !.not.lmask
!$OMP     PARALLEL DO PRIVATE(j,i) &
!$OMP              SCHEDULE(STATIC,jblk)
          do j= 1,jj
            wminy(j)= spval
            wmaxy(j)=-spval
            do i= 1,ii
              htmp(i+(j-1)*ii) = h(i,j)
              if     (htmp(i+(j-1)*ii).ne.spval) then
                wminy(j)=min(wminy(j),htmp(i+(j-1)*ii))
                wmaxy(j)=max(wmaxy(j),htmp(i+(j-1)*ii))
              endif
#if defined(REAL4)
! ---         h(i,j) = htmp(i+(j-1)*ii)  ! h is already real*4
#else
              h(i,j) = htmp(i+(j-1)*ii)  ! h is not real*4, so update it
#endif
            enddo !i
#if defined(ENDIAN_IO)
            call zaio_endian(htmp(1+(j-1)*ii),ii)  !swap to big-endian
#endif
          enddo !j
        endif !lmask:else
      else !.not.lreal4
        if     (lmask) then
!$OMP     PARALLEL DO PRIVATE(j,i) &
!$OMP              SCHEDULE(STATIC,jblk)
          do j= 1,jj
            wminy(j)= spval
            wmaxy(j)=-spval
            do i= 1,ii
              if     (mask(i,j).ne.0) then
                htmp(i+(j-1)*ii) = h(i,j)
                wminy(j)=min(wminy(j),htmp(i+(j-1)*ii))
                wmaxy(j)=max(wmaxy(j),htmp(i+(j-1)*ii))
              else
                htmp(i+(j-1)*ii) = spval
              endif
            enddo !i
#if defined(ENDIAN_IO)
            call zaio_endian(htmp(1+(j-1)*ii),ii)  !swap to big-endian
#endif
          enddo !j
        else !.not.lmask
!$OMP     PARALLEL DO PRIVATE(j,i) &
!$OMP              SCHEDULE(STATIC,jblk)
          do j= 1,jj
            wminy(j)= spval
            wmaxy(j)=-spval
            do i= 1,ii
              htmp(i+(j-1)*ii) = h(i,j)
              if     (htmp(i+(j-1)*ii).ne.spval) then
                wminy(j)=min(wminy(j),htmp(i+(j-1)*ii))
                wmaxy(j)=max(wmaxy(j),htmp(i+(j-1)*ii))
              endif
            enddo !i
#if defined(ENDIAN_IO)
            call zaio_endian(htmp(1+(j-1)*ii),ii)  !swap to big-endian
#endif
          enddo !j
        endif !lmask:else
      endif !lreal4:else
!
      rmin(1) = minval(wminy(1:jj))
      rmax(1) = maxval(wmaxy(1:jj))
      call xcminr(rmin)
      call xcmaxr(rmax)
      hmin = rmin(1)
      hmax = rmax(1)
!
! --- I/O from first processor in each row.
#if defined(ENDIAN_IO)
! --- htmp and data_void are already big-endian
#endif
!
      vsave4 = vland4
      vland4 = data_void(1)
      call xcaget4(w,htmp, -1)  !htmp to w (as a 2-d array) for each row.
      vland4 = vsave4
!
      if     (mproc.eq.mp_1st) then
        if     (nproc.eq.jpr) then
          do i= itdm*jtdm+1,n2drec
            w(itdm*jj+i-itdm*jtdm) = data_void(1)
          enddo
          lrec = n2drec - itdm*j0
        else
          lrec = itdm*jj
        endif
!
        disp = n2drec
        disp = (iarec(iaunit)-1)*disp + itdm*j0
!       call mpi_file_write_at(iahand(iaunit),
        call mpi_file_write_at_all(iahand(iaunit), &
                               disp, &
                               w(1), &
                               lrec, &
                               MTYPE4, &
                               mpistat(1,1), &
                               mpierr)
        if     (mpierr.ne.0) then
          write(lp,9100) iarec(iaunit),iaunit
          write(lp,*) 'mpierr = ',mpierr
          call flush(lp)
          call xchalt('(zaiowr)')
                 stop '(zaiowr)'
        endif !mpierr
      endif !I/O from first processor in each row
!
#if defined(TIMER)
!
      call xctmr1(18)
#endif
      return
!
 9000 format(/ /10x,'error in zaiowr -  array I/O unit ', &
         i3,' is not marked as open.'/ /)
 9100 format(/ /10x,'error in zaiowr -  can''t write record', &
         i4,' on array I/O unit ',i3,'.'/ /)
      end subroutine zaiowr
!
!
!> Revision history:
!>
!> Nov  2012 - iahand in separate common block
!> Feb  2015 - reduced size of w, allocated on 1st tile in each row only
!> July 2017 - added zaiordg
!> Aug  2018 - corrected size of value and key