program main

!*****************************************************************************80
!
!! MAIN is the main program for UNIFORM_DATASET.
!
!  Discussion:
!
!    UNIFORM_DATASET generates a uniform random dataset and writes it to a file.
!
!    This program is meant to be used interactively.  It's also
!    possible to prepare a simple input file beforehand and use it
!    in batch mode.
!
!    The program requests input values from the user:
!
!    * M, the spatial dimension,
!    * N, the number of points to generate,
!    * SEED, the seed, a positive integer.
!
!    The program generates the data, writes it to the file
!
!      uniform_M_N.txt
!
!    where "M" and "N" are the numeric values specified by the user,
!    and then asks the user for more input.   To indicate that no further
!    computations are desired, it is enough to input a nonsensical
!    value, such as -1.
!
!  Modified:
!
!    31 May 2007
!
!  Author:
!
!    John Burkardt
!
  implicit none

  character ( len = 80 ) :: file_out_name
  integer ( kind = 4 ) ios
  integer ( kind = 4 ) m
  integer ( kind = 4 ) n
  real    ( kind = 8 ), allocatable, dimension ( :, : ) :: r
  integer ( kind = 4 ) seed
  integer ( kind = 4 ) seed_init

  call timestamp ( )

  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'UNIFORM_DATASET'
  write ( *, '(a)' ) '  FORTRAN90 version'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '  Generate a uniform random dataset.'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '  This program is meant to be used interactively.'
  write ( *, '(a)' ) '  It is also possible to prepare a simple input'
  write ( *, '(a)' ) '  file beforehand and use it in batch mode.'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '  The program requests input values from the user:'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '  * M, the spatial dimension,'
  write ( *, '(a)' ) '  * N, the number of points to generate,'
  write ( *, '(a)' ) '  * SEED, a positive integer.'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '  The program generates the data, '
  write ( *, '(a)' ) '  writes it to the file'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '    uniform_M_N.txt'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '  where "M" and "N" are the numeric values specified'
  write ( *, '(a)' ) '  by the user, and then asks the user for more input.'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '  To indicate that no further computations are'
  write ( *, '(a)' ) '  desired, it is enough to input a nonsensical value,'
  write ( *, '(a)' ) '  such as -1.'

  do

    write ( *, '(a)' ) '  *'
    write ( *, '(a)' ) ' *'
    write ( *, '(a)' ) '*  Ready to generate a new dataset:'
    write ( *, '(a)' ) ' *'
    write ( *, '(a)' ) '  *'

    write ( *, '(a)' ) ' '
    write ( *, '(a)' ) '  Enter M, the spatial dimension:'
    write ( *, '(a)' ) '  (Try "2" if you don''t have a preference.)'
    write ( *, '(a)' ) '  (0 or any negative value terminates execution.)'

    read ( *, *, iostat = ios ) m

    if ( ios /= 0 ) then
      write ( *, '(a)' ) ' '
      write ( *, '(a)' ) 'UNIFORM_DATASET - Fatal error!'
      write ( *, '(a)' ) '  An I/O error occurred while reading M.'
      exit
    end if

    if ( m <= 0 ) then
      write ( *, '(a)' ) ' '
      write ( *, '(a)' ) 'UNIFORM_DATASET:'
      write ( *, '(a)' ) '  The value of M is interpreted as a request'
      write ( *, '(a)' ) '  for termination.'
      exit
    end if

    write ( *, '(a)' ) ' '
    write ( *, '(a)' ) '  Enter N, the number of points to generate:'
    write ( *, '(a)' ) '  (Try "25" if you don''t have a preference.)'
    write ( *, '(a)' ) '  (0 or any negative value terminates execution).'

    read ( *, *, iostat = ios ) n

    if ( ios /= 0 ) then
      write ( *, '(a)' ) ' '
      write ( *, '(a)' ) 'UNIFORM_DATASET - Fatal error!'
      write ( *, '(a)' ) '  An I/O error occurred while reading N.'
      exit
    end if

    if ( n <= 0 ) then
      write ( *, '(a)' ) ' '
      write ( *, '(a)' ) 'UNIFORM_DATASET:'
      write ( *, '(a)' ) '  The value of N is interpreted as a request'
      write ( *, '(a)' ) '  for termination.'
      exit
    end if

    write ( *, '(a)' ) ' '
    write ( *, '(a)' ) '  Enter SEED, the initial seed for UNIFORM,'
    write ( *, '(a)' ) '  a portable uniform random number generator:'
    write ( *, '(a)' ) '  (0 will cause the program to pick a value for you).'
    write ( *, '(a)' ) '  (a negative value terminates execution.)'

    read ( *, *, iostat = ios ) seed

    if ( ios /= 0 ) then
      write ( *, '(a)' ) ' '
      write ( *, '(a)' ) 'UNIFORM_DATASET - Fatal error!'
      write ( *, '(a)' ) '  An I/O error occurred while reading IOS.'
      exit
    end if

    if ( seed < 0 ) then
      write ( *, '(a)' ) ' '
      write ( *, '(a)' ) 'UNIFORM_DATASET:'
      write ( *, '(a)' ) '  The value of SEED is interpreted as a request'
      write ( *, '(a)' ) '  for termination.'
      exit
    end if

    if ( seed == 0 ) then
      call get_seed ( seed )
      write ( *, '(a)' ) ' '
      write ( *, '(a,i12)' ) '  Chosen value of SEED = ', seed
    end if

    allocate ( r(1:m,1:n) )

    seed_init = seed

    call r8mat_uniform_01 ( m, n, seed, r )

!   write ( file_out_name, '(a,i2,a,i5,a)' ) 'uniform_', m, '_', n, '.txt'

    write ( file_out_name, '(a,i2.2,a,i5.5,a)' ) 'uniform_', m, '_', n, '.txt'

    call r8mat_uniform_write ( m, n, seed_init, seed, r, file_out_name )

    deallocate ( r )

    write ( *, '(a)' ) ' '
    write ( *, '(a)' ) '  The data was written to the file "' &
       // trim ( file_out_name ) // '".'

  end do

  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'UNIFORM_DATASET'
  write ( *, '(a)' ) '  Normal end of execution.'

  write ( *, '(a)' ) ' '
  call timestamp ( )

  stop
end