program main

!*****************************************************************************80
!
!! test_lls_test() tests test_lls().
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    31 October 2011
!
!  Author:
!
!    John Burkardt
!
  implicit none

  call timestamp ( )
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'test_lls_test():'
  write ( *, '(a)' ) '  FORTRAN90 version'
  write ( *, '(a)' ) '  Test the TEST_LLS library.'

  call test01 ( )
!
!  Terminate.
!
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'TEST_LLS_TEST'
  write ( *, '(a)' ) '  Normal end of execution.'
  write ( *, '(a)' ) ' '
  call timestamp ( )

  stop 0
end
subroutine test01 ( )

!*****************************************************************************80
!
!! TEST01 summarizes the test data.
!
!  Licensing:
!
!    This code is distributed under the MIT license.
!
!  Modified:
!
!    16 April 2012
!
!  Author:
!
!    John Burkardt
!
  implicit none

  integer, parameter :: rk = kind ( 1.0D+00 )

  real ( kind = rk ), allocatable :: a(:,:)
  real ( kind = rk ), allocatable :: b(:)
  real ( kind = rk ) b_norm
  integer m
  integer n
  integer prob
  integer prob_num
  real ( kind = rk ), allocatable :: r(:)
  real ( kind = rk ) r_norm
  real ( kind = rk ) r8vec_norm
  real ( kind = rk ), allocatable :: x(:)
  real ( kind = rk ) x_norm

  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'TEST01'
  write ( *, '(a)' ) '  Get each least squares test and compute the maximum residual.'
  write ( *, '(a)' ) '  The L2 norm of the residual MUST be no greater than'
  write ( *, '(a)' ) '  the L2 norm of the right hand side, else 0 is a better solution.'

  call p00_prob_num ( prob_num )

  write ( *, '(a)' ) ' '
  write ( *, '(a,i4)' ) '  Number of problems = ', prob_num
  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) '  Index     M     N     ||B||         ||X||         ||R||'
  write ( *, '(a)' ) ' '

  do prob = 1, prob_num

    call p00_m ( prob, m )
    call p00_n ( prob, n )

    allocate ( a(1:m,1:n) )
    allocate ( b(1:m) )
    allocate ( x(1:n) )
    allocate ( r(1:m) )

    call p00_a ( prob, m, n, a )
    call p00_b ( prob, m, b )
    call p00_x ( prob, n, x )

    r(1:m) = matmul ( a(1:m,1:n), x(1:n) ) - b(1:m)

    b_norm = r8vec_norm ( m, b )
    x_norm = r8vec_norm ( n, x )
    r_norm = r8vec_norm ( m, r )

    write ( *, '(2x,i5,2x,i4,2x,i4,2x,g12.4,2x,g12.4,2x,g12.4)' ) prob, m, n, b_norm, x_norm, r_norm

    deallocate ( a )
    deallocate ( b )
    deallocate ( r )
    deallocate ( x )

  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