react_modify command

Syntax:

react_modify keyword values ...

  • one or more keyword/value pairs may be listed

  • keywords = recomb or rboost

    recomb value = yes or no = enable or disable defined recombination reactions
rboost value = rfactor
  rfactor = boost probability of recombination reactions by this factor

Examples:

react_modify recomb no
react_modify rboost 100.0

Description:

Set parameters that affect how reactions are performed.

The recomb keyword turns on or off recombination reactions. It is only relevant if recombination reactions were defined in the reaction file read in by the react command. If the setting is no then they will be disabled even if they were listed in the reaction file. This is useful to turn recombination reactions off, to see if they affect simulation results.

The rboost keyword is a setting for recombination reactions. It is ignored if no recombination reactions exist, or the recomb keyword is set to no. The rboost setting does not affect the overalll statistical results of recombination reactions, but tries to improve their computational efficiency. Recombination reactions typically occur with very low probability, which means the code spends time testing for reactions that rarely occur. If the rfactor is set to N > 1, then recombination reactions are skipped N-1 out of N times, when one or more such reactions is defined for a pair of colliding particles. A random number us used to select on that probability. To compensate, when a recombination reaction is actually tested for occurrence, its rate is boosted by a factor of N, making it N times more likely to occur.

The smallest value rboost can be set to is 1.0, which effectively applies no boost factor.

Important

Setting rboost too large could meant the probability of a recombination reaction becomes > 1.0, when it is does occur. SPARTA does not check for this, so you should estimate the largest boost factor that is safe to use for your model.

Restrictions:

none

Default:

The option defaults are recomb = yes and rboost = 1000.0.