MPL for Windows Manual

Change XPRESS MIP Strategy Options

You can change the MIP Strategy options for XPRESS by choosing XPRESS parameters from the Options menu and then pressing the MIP Strategies tab. This will display the MIP strategy options for XPRESS in the dialog box as shown below:

Nodeset Selection

The Nodeset selection option has the following possible selections:

Local first search	Choose among the two descendant nodes, 
                        if none among all active nodes (default).

Best first search       Branch variable automatically selected. 
			
Depth first search      Depth-first search exploring both descendants first. 

First best first,	       
  then local first, 	       
Switch after n nodes    All nodes are considered for the first n nodes, 
                        after which local first search is resumed. 
   

Node Selection

The Node selection option has the following possible selections:

Best estimate           If a target object function has not been set, 
                        choose the node with the best estimate target object 
                        function for global.  If a target objective function has 
                        is been set (by the user or from a previous IP solution), 
                        the choice is based on the Forrest-Hirst-Tomlin Criterion.

                        The Target obj. function used in "best estimate" node selection 
                        technique.  This is set automatically after solving the LP 
                        relaxation unless set by the user.

Smallest solution       Always choose the node with smallest estimated solution. 
			
Smallest bound          Always choose the node with smallest bound (default).  
 

Relative Gap

The relative MIP optimality stopping criterion.

The MIP search will stop if the relative optimality gap, ABS(best solution - best bound) / best bound, is less than or equal to this criterion value. The default is 0.0.

Absolute Gap

The absolute MIP optimality stopping criterion. The MIP search will stop if the absolute optimality gap, ABS(best solution - best bound), is less than or equal to this crietrion value. The default is 0.0.

Degradation Estimate

Degradation Estimate is the node selection degredator estimate control. The Degradation Estimate option has the following possible selections:

Sum min (up, down) (default)

Sum (up + down)

Sum ((2 min (up,down) + max (up, down))  

Sum max (up, down)  

Sum down  

Sum up  
  

Estimate deg. Mult

Factor to multiply estimated degradations by, default is 1.0.

Default Pseudo Cost

Default pseudo cost used in node degradation estimation, default is 0.01.