program main

!****************************************************************************80
!
!! comp_next_test() tests comp_next().
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    21 December 2009
!
!  Author:
!
!    John Burkardt
!
!  Reference:
!
!    Fabio Nobile, Raul Tempone, Clayton Webster,
!    A Sparse Grid Stochastic Collocation Method for Partial Differential
!    Equations with Random Input Data,
!    SIAM Journal on Numerical Analysis,
!    Volume 46, Number 5, 2008, pages 2309-2345.
!
  implicit none

  integer, parameter :: test_num = 12

  integer dim_num
  integer :: dim_num_array(test_num) = (/ &
    2, 2, 2, 2, 2, &
    3, 3, 3, 3, 3, &
    4, 4 /)
  integer level_max
  integer :: level_max_array(test_num) = (/ &
    0, 1, 2, 3, 4, &
    0, 1, 2, 3, 4, &
    2, 3 /)
  integer test

  call timestamp ( )
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'COMP_NEXT_TEST'
  write ( *, '(a)' ) '  FORTRAN90 version'
  write ( *, '(a)' ) '  Call COMP_NEXT_TEST with various arguments..'

  do test = 1, test_num

    dim_num = dim_num_array(test)
    level_max = level_max_array(test)
    call comp_next_test ( dim_num, level_max )

  end do
!
!  Terminate.
!
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'COMP_NEXT_TEST'
  write ( *, '(a)' ) '  Normal end of execution.'
  write ( *, '(a)' ) ' '
  call timestamp ( )

  stop 0
end
subroutine comp_next_test ( dim_num, level_max )

!****************************************************************************80
!
!! COMP_NEXT_TEST tests COMP_NEXT, which computes 1D level vectors.
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    23 August 2009
!
!  Author:
!
!    John Burkardt
!
!  Parameters:
!
!    Input, integer DIM_NUM, the spatial dimension.
!
!    Input, integer LEVEL_MAX, the maximum level.
!
  implicit none

  integer dim_num

  integer h
  integer i
  integer level
  integer level_1d(dim_num)
  integer level_max
  integer level_min
  logical more_grids
  integer t

  level_min = max ( 0, level_max + 1 - dim_num )

  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'COMP_NEXT_TEST'
  write ( *, '(a)' ) '  COMP_NEXT generates, one at a time, vectors'
  write ( *, '(a)' ) '  LEVEL_1D(1:DIM_NUM) whose components add up to LEVEL.'
  write ( *, '(a)' ) ' '
  write ( *, '(a,i8,a,i8)' ) '  We call with:'
  write ( *, '(a,i8)' ) '  DIM_NUM = ', dim_num
  write ( * , '(2x,i8,a,i8)' ) level_min, &
    ' = LEVEL_MIN <= LEVEL <= LEVEL_MAX = ', level_max
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '     LEVEL     INDEX  LEVEL_1D Vector'
!
!  The outer loop generates values of LEVEL from LEVEL_MIN to LEVEL_MAX.
!
  do level = level_min, level_max

    write ( *, '(a)' ) ' '
!
!  The inner loop generates vectors LEVEL_1D(1:DIM_NUM) whose components
!  add up to LEVEL.
!
    more_grids = .false.
    h = 0
    t = 0
    i = 0

    do

      call comp_next ( level, dim_num, level_1d, more_grids, h, t )

      i = i + 1
      write ( *, '(2x,i8,2x,i8,6(2x,i8))'  ) level, i, level_1d(1:dim_num)

      if ( .not. more_grids ) then
        exit
      end if

    end do

  end do

  return
end
subroutine timestamp ( )

!*****************************************************************************80
!
!! timestamp() prints the current YMDHMS date as a time stamp.
!
!  Example:
!
!    31 May 2001   9:45:54.872 AM
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    15 August 2021
!
!  Author:
!
!    John Burkardt
!
  implicit none

  character ( len = 8 ) ampm
  integer d
  integer h
  integer m
  integer mm
  character ( len = 9 ), parameter, dimension(12) :: month = (/ &
    'January  ', 'February ', 'March    ', 'April    ', &
    'May      ', 'June     ', 'July     ', 'August   ', &
    'September', 'October  ', 'November ', 'December ' /)
  integer n
  integer s
  integer values(8)
  integer y

  call date_and_time ( values = values )

  y = values(1)
  m = values(2)
  d = values(3)
  h = values(5)
  n = values(6)
  s = values(7)
  mm = values(8)

  if ( h < 12 ) then
    ampm = 'AM'
  else if ( h == 12 ) then
    if ( n == 0 .and. s == 0 ) then
      ampm = 'Noon'
    else
      ampm = 'PM'
    end if
  else
    h = h - 12
    if ( h < 12 ) then
      ampm = 'PM'
    else if ( h == 12 ) then
      if ( n == 0 .and. s == 0 ) then
        ampm = 'Midnight'
      else
        ampm = 'AM'
      end if
    end if
  end if

  write ( *, '(i2.2,1x,a,1x,i4,2x,i2,a1,i2.2,a1,i2.2,a1,i3.3,1x,a)' ) &
    d, trim ( month(m) ), y, h, ':', n, ':', s, '.', mm, trim ( ampm )

  return
end