program main

!*****************************************************************************80
!
!! MAIN is the main program for SOBOL_DATASET.
!
!  Discussion:
!
!    SOBOL_DATASET generates a Sobol dataset and writes it to a file.
!
!  Licensing:
!
!    This code is distributed under the GNU LGPL license. 
!
!  Modified:
!
!    03 August 2004
!
!  Author:
!
!    John Burkardt
!
  implicit none

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

  call timestamp ( )

  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'SOBOL_DATASET'
  write ( *, '(a)' ) '  FORTRAN90 version.'
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '  Generate a Sobol quasirandom dataset.'

  do

    write ( *, '(a)' ) ' '
    write ( *, '(a)' ) '  Enter M, the spatial dimension:'
    write ( *, '(a)' ) '  (0 or any negative value terminates execution).'

    read ( *, *, iostat = ios ) m

    if ( ios /= 0 ) then
      exit
    end if

    if ( m <= 0 ) then
      exit
    end if

    write ( *, '(a)' ) ' '
    write ( *, '(a)' ) '  Enter N, the number of points to generate:'
    write ( *, '(a)' ) '  (0 or any negative value terminates execution).'

    read ( *, *, iostat = ios ) n

    if ( ios /= 0 ) then
      exit
    end if

    if ( n <= 0 ) then
      exit
    end if

    write ( *, '(a)' ) ' '
    write ( *, '(a)' ) '  Enter SKIP, the number of initial points to skip:'
    write ( *, '(a)' ) '  (0 is a common choice).'
    write ( *, '(a)' ) '  (Another is the least power of 2 greater than'
    write ( *, '(a)' ) '   or equal to N.)'
    write ( *, '(a)' ) '  (a negative value terminates execution.)'

    read ( *, *, iostat = ios ) skip

    if ( ios /= 0 ) then
      exit
    end if

    if ( skip < 0 ) then
      exit
    end if

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

    call i8_sobol_generate ( m, n, skip, r )

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

    call i8_sobol_write ( m, n, skip, r, file_out_name )

    deallocate ( r )

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

  end do

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

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

  stop
end