# 17. Multicriteria Rebalance

This chapter describes how to use the multicriteria rebalance capability in Sierra/SM.

When running a typical Sierra/SM analysis, there are many capabilities that have a much higher computational cost than the other capabilities used in the simulation. An example of such capabilities is contact. Because contact typically does not occur on every element in the finite element model, the mesh can be decomposed (rebalanced) to split the contact work up across as many processors as possible to run most efficiently. This rebalance can occur at a user defined interval to account for contact patches coming in and out of contact with each other (consider a tire rolling on the ground), or it can be done automatically. Multicriteria rebalance also takes into account more expensive element formulations.

To activate multicriteria rebalance, use the following command:

    BEGIN REBALANCE
      INITIAL REBALANCE = ON
      PERIODIC REBALANCE = AUTO
      LOAD RATIO THRESHOLD = 1.25
      REBALANCE STRATEGY = MULTICRITERIA
    END

Warning

`REBALANCE STRATEGY = MULTICRITERIA` is still an experimental capability and should be used with caution.

Known Issue

`REBALANCE STRATEGY = MULTICRITERIA` does not currently work with restart.