Restart the step:

• Choose a new maximum step length so that
  • predicted total step length < safety OR
  • predicted deviation < d_miss
• Call AlongStepGetPhysicalInteractionLength methods of all processes again
• Call all DoIt action and recheck criteria
  • If accepted, good
  • If second failure, write warning and take a “default” action

If total sum < safety

• use the sum position change directly

If not,

• then move the particle by primary move and check whether a volume change occurs.
  • If not apply the “pertubing” move, starting from end of primary move

Process writers are responsible:

• to make clear their assumptions
• to document which other processes they can cooperate with.

Simulators must:

• ensure processes they choose can cooperate

Allow several processes to propose a position change in AlongStep action

The Stepping Manager will:

• keep the vector sum of these changes
• find the process with the biggest move
  • treat it as the “main” change
  • treat the sum of other changes as “pertubation”

At the end of AlongStep loop the Stepping Manager will accept the step if either

• the sum of changes is within safety OR
• the “perturbing” sum is smaller than d_miss
  • could check that it is smaller than “main” move

If either condition holds, the step will be accepted, and the track will move

Allow several processes to propose a position change in AlongStepDoIt

• coherently
• safely: without skipping volumes
• efficiently: no slowdown for “default”

Make the Relocation into

• PostStepDoIt of Transportation

Position changes are proposed:

• transportation in an AlongStep action
• any process in a PostStep action

Stepping Manager does Relocation

Processes that propose AlongStep position changes must “cooperate”:

They must be:

• independent
• accumulated roughly linearly along the length of a step