While loop

LAMMPS LAMMPS General Discussion
1

Hi
I was wondering how can one define a “while loop” in LAMMPS?
I guess it can be a mixture of “variable loop” and “if” commands.
any ideas?
yours

2

Exactly, within the loop you can have an if statement that jumps to a spot outside the loop. For something like a convergence loop you could do the following until your convergence conditions are met

compute pe all pe/atom
compute ke all ke/atom
compute cpe all reduce ave c_pe
compute cke all reduce ave c_ke

label converge_loop
variable converge_step loop 10
      # do things

      # if per atom energy is less than x, force convergence to continue
      variable totalstep equal c_cke+c_cpe
      # if first step, previous total energy is sufficiently large to prevent convergence.
      if "${converge_step}==1 " then "variable totalprev equal 30000.0"
      # percent difference of n and n-1 step
      variable diff equal abs(${totalprev}-${totalstep})/${totalprev}*100
      print "%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%"
      print "Previous Total Energy : ${totalprev}"
      print "Current Total Energy  : ${totalstep}"
      print "Percent Difference : ${diff}"
      variable totalprev equal ${totalstep}
      # if less than 1% difference, consider it converged
      if "${diff}<1.0" then "jump SELF converge_break"
      print "%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%"

  next converge_step
  jump SELF converge_loop
  label converge_break
3 Likes
3

@tjbarrett Thanks for the tip. I have followed your instruction to create random atoms and delete them if too close (within critical distance). However I receive an error when jumping to first label. Any idea?

> label       AddingLoopSart
> 
> variable    AddingLoopCount loop 1000
> 
> 	if "${AddingLoopCount}==1 " then "variable OverlapCheck equal 0"
> 	create_atoms		1 random 1 123456789 AddRegion
> 	variable AddedSiaId equal ${BeforeAddCountAll}+1
> 	group AddedSiaGroup id ${AddedSiaId}
> 	delete_atoms overlap ${CriticalAtomicDist} AddedSiaGroup BeforeAddGroup
> 	variable AfterAddCountAll  equal count(all)
> 	variable OverlapCheck equal ${AfterAddCountAll}-${BeforeAddCountAll}
> 	print 'AdditionIsOverlap!!!'
> 	if "${OverlapCheck}==1" then &
> 		"jump SELF AddingLoopBreak" &
> 	else &
> 		"next AddingLoopCount" &
> 		"jump SELF AddingLoopSart" &
> 
> label AddingLoopBreak

ERROR: Label wasn’t found in input script (src/input.cpp:237)
Last command:

4

Are you using lmp -in in.input or lmp < in.input?
The latter is not always reliable, especially when running in parallel.

1 Like
5

@akohlmey that was the case! thanks!