module data
  !--------------------------------------------------------------------------------------------------
  ! This module holds most of the data needed for postprocessing, with the exception of work arrays
  !--------------------------------------------------------------------------------------------------
  implicit none
  save
  !--------------------------------------------------------------------------------------------------
  ! Array sizes
  !--------------------------------------------------------------------------------------------------
  integer(4) :: mx    ! Number of modes in the x direction mx = 2*mgalx/3 
  integer(4) :: my    ! Number of modes in the y direction
  integer(4) :: mz    ! Number of modes in the z direction mz = 2*mgalz/3 - 1

  integer(4) :: mgalx ! Number of modes for dealiasing in the x-direction (collocation points)
  integer(4) :: mgalz ! Number of modes for dealiasing in the z-direction (collocation points)
  integer(4), parameter :: debug = 0
  integer(4)  sml 
  !--------------------------------------------------------------------------------------------------
  ! 1,2,3 digit numbers for io  
  !--------------------------------------------------------------------------------------------------
  character(1) dig1(10) ! 1 digit numbers
  character(2) dig2(100) ! 2 digit numbers
  character(3) dig3(1000) ! 3 digit numbers
  !--------------------------------------------------------------------------------------------------
  ! The zero modes for the u,w velocities
  !--------------------------------------------------------------------------------------------------
  real(4), allocatable, dimension(:) :: u00, w00
  !--------------------------------------------------------------------------------------------------
  ! A few parameters of the simulation
  !--------------------------------------------------------------------------------------------------
  real(8) :: time  ! Large field (only double precision variable!)
  real(4) :: Re ! Reynolds number of the simulation
  real(4) :: retau ! Reynolds number based on utau and h
  real(4) :: utau
  real(4) :: lx ! length of box in x direction
  real(4) :: lz ! length of box in z direction
  real(4) :: a0 ! I have no idea of what this is
  integer(4) :: fieldno ! field number , ranging from first_field to last_field 
  integer(4) :: first_field ! field number of the first field to be read in
  integer(4) :: last_field  ! field number of the last field to be read in

  !--------------------------------------------------------------------------------------------------
  ! Used to scale the wavenumbers
  !--------------------------------------------------------------------------------------------------
  real(4) :: alpha    ! This is 1/(x_length)
  real(4) :: beta     ! This is 1/(y_length)

  !--------------------------------------------------------------------------------------------------
  ! Indexes which make wavenumber handling easier
  !--------------------------------------------------------------------------------------------------
  real(8), allocatable, dimension(:)    :: alp2    ! The kx wavenumber squared for a certain mode (0:mx/2-1)
  ! Allocated in generate_indices
  ! Deallocated in io.f90, subroutine cleanup
  real(8), allocatable, dimension(:)    :: bet2    ! The kz wavenumber squared for a certain mode (0:mz-1)
  ! Allocated in generate_indices
  ! Deallocated in io.f90, subroutine cleanup
  real(8), allocatable, dimension(:)    :: kx, kz  ! Wavenumbers kx and kz, scaled apropriately
  ! Allocated in generate_indices
  ! Deallocated in io.f90, subroutine cleanup
  !--------------------------------------------------------------------------------------------------
  ! Useful constants
  !--------------------------------------------------------------------------------------------------
  real(8), parameter :: pi=3.14159265358979323846Q0 
  !--------------------------------------------------------------------------------------------------
  ! True and False values
  !--------------------------------------------------------------------------------------------------
  integer, parameter :: true = 1
  integer, parameter :: false = 0 
contains	
  !--------------------------------------------------------------------------------------------------
  subroutine generate_indices()
    !--------------------------------------------------------------------------------------------------
    ! This subroutine generates the indices that will be used in the Poisson solution
    !--------------------------------------------------------------------------------------------------		
    implicit none

    integer(4) :: i, k

    allocate (alp2(0:(mx/2)-1), bet2(0:mz-1))
    allocate (kx(0:(mx/2)-1), kz(0:mz-1))

    do k = 0, (mz - 1)/2
       bet2(k) = (beta*k)**2
       kz(k)  = beta*k
    end do

    do k = (mz + 1)/2, mz - 1 
       kz(k)   = beta*(k - mz)
       bet2(k) = (beta*(k - mz))**2
    end do

    do i = 0, (mx/2)-1
       kx(i)   = alpha*i
       alp2(i) = (alpha*i)**2
    end do

  end subroutine generate_indices

end module data