! Module file: resetvariances
!
! CNS module
! **********
!
! Authors: Piet Gros and Axel T. Brunger
!
! copyright Yale University
!
! Function:
! Set small variances to &zerovar to avoid division by zero.
!
! Requirements:
! 1. This module can only be used from within xray.
! 

module {resetvariances}
(
   &resetzero=0.01;     {reset zero variances to &resetzero, to avoid division
                        by zero}

   &zerovar=0.01;       {smallest significant value. For example, the smallest
                         digit defined by the diffraction data.}

   &sel=(all);          {structure factor selection for phase set}

   &var;                {variance array}
)

checkversion 1.3

if (&resetzero # 0) then

   do (&var=&resetzero) (&var < &zerovar and &sel)
   if ($select > 0) then
      display RESETVARIANCES-INFO: $select phase-set variances &var of value < &zerovar set to &resetzero
   end if
   do (&var=&resetzero) (&var < &zerovar and not (&sel) )

end if