The following changes have been made to RiverWare optimization.

When RiverWare formulates the internal representation of the optimization problem, values are represented in optimization units. The optimization units are similar to RiverWare standard units but with scaling factors specific to optimization applied. Proper scaling of the optimization problem is important for numeric stability. Improper scaling can result in improper freezing and, subsequently, infeasible solutions.

Previously, the optimization unit scaling factors were hard-coded in RiverWare. Now, you can modify the scaling factors in the Optimization Run Parameters. Modifying the optimization unit scaling can be important for maintaining proper scaling in models with a 5 Minute or 15 Minute timestep. See Optimization Units and Scaling in Optimization for more information.

When coefficients on variables in the internal representation of a Minimize or Maximize objective function are too small, improper freezing and, subsequently, infeasible solutions can result. RiverWare now issues a warning message if any coefficients in a Minimize or Maximize objective function are below a specified threshold value. The default threshold is 0.0001, and you can modify this in the Optimization Run Parameters. The warning message also indicates the minimal multiplier that must be applied in the RPL objective function expression so all coefficients will be larger than the threshold.