! Module file: fft_parameter_check
!
! Function: determines the optimum setting for the B-factor inflation
! given the high resolution limit, the gridding factor, and the minimum
! B-factor of the model.   It also determines the recommended ELIM parameter
! as a function of the high resolution limit. 
! 
! Reference: 
! 
! Gerard Bricogne (2001),
!   International Tables for Crystallography, Volume B, 2001, p. 87
!
! CNS module
! **********
!
! Authors: Axel T. Brunger and Paul D. Adams
!
! copyright Yale University
!
! Requirements:
! This module can only be used from the main level of CNS. 
!
! 08/03/06 ATB

module {fft_parameter_check}
(
 &b_min=0;              {input: minimum B-factor of model}                        
 &d_min=1.0;            {input: high resolution limit}
 &q_factor=100;         {input: quality factor - 100 for 1% accuracy}
 &grid=auto;            {input: if "auto" gridding factor is set automatically}
                        {       otherwise gridding factor set to <number>  }
 &fft_memory=-1;        {input: fft memory; if "-1" use automatic mode }
 
 &fft_grid=$fft_grid;   {output: fft gridding factor}
 &fft_b_add=$fft_b_add; {output: fft B addition}
 &fft_elim=$fft_elim;   {output: fft elimit factor}
 
)
 
 set message ? end
 evaluate ($message_old=$result)
 set echo ? end
 evaluate ($echo_old=$result)
 if ( $log_level = verbose ) then
   set echo=on message=normal end
 else
   set echo=off message=off end
 end if



 checkversion 1.3

 if (&grid=auto) then
  { - adjust gridding factor such that the absolute grid is at least 1 A -}
  xray 
     evaluate (&fft_grid = min ( 0.3333, 1 / &d_min ) ) 
  end
 else
  evaluate (&fft_grid=&grid)
 end if
    
 xray
    fft grid=&fft_grid end
 end
  
 evaluate ($fft_sigma=1/ ( 2 * &fft_grid) )
 
 evaluate ($fft_b_base=log10(&q_factor) / ( $fft_sigma * ($fft_sigma-1) / &d_min^2) )
 
 evaluate (&fft_b_add=max(0,$fft_b_base-&b_min) )
  
 xray
    fft
       bscale=&fft_b_add
    end
 end
 
 if (&d_min < 0.7 ) then
    evaluate (&fft_elim=18)
 elseif (&d_min < 0.8 ) then
    evaluate (&fft_elim=16) 
 elseif (&d_min < 0.9 ) then
    evaluate (&fft_elim=14) 
 elseif (&d_min < 1.0 ) then
    evaluate (&fft_elim=12)
 elseif (&d_min < 1.2 ) then
    evaluate (&fft_elim=11)
 elseif (&d_min < 1.5 ) then
    evaluate (&fft_elim=10) 
 else
    evaluate (&fft_elim=8)
 end if
 
 xray
    fft
       elim=&fft_elim
    end
    fft
      if ( &fft_memory < 0 ) then
       display  fft_parameter_check: using automatic memory option
       automemory=true
      else
       display  fft_parameter_check: memory = &fft_memory
       memory=&fft_memory
      end if
    end
 end


 
 display  fft_parameter_check: minimum model B-factor = &b_min  A^2
 display  fft_parameter_check: high resolution limit = &d_min  A
 display  fft_parameter_check: fft gridding factor set to &fft_grid
 display  fft_parameter_check: fft B factor offset set to &fft_b_add  A^2
 display  fft_parameter_check: fft Elimit factor set to &fft_elim
  
 set message=$message_old echo=$echo_old end