An ORD formatted file specifies in which order the mixed integer optimizer branches on variables. The format of an ORD file is shown in Figure G.1. In the figure names in capitals are keywords of the ORD format, whereas names in brackets are custom names or values. The ?? is an optional key specifying the preferred branching direction. The possible keys are DN and UP which indicate that down or up is the preferred branching direction respectively. The branching direction key is optional and is left blank the mixed integer optimizer will decide whether to branch up or down.
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A concrete example of a ORD file is presented below:
NAME EXAMPLE DN x1 2 UP x2 1 x3 10 ENDATA
This implies that the priorities 2, 1, and 10 are assigned to variable x1, x2, and x3 respectively. The higher the priority value assigned to a variable the earlier the mixed integer optimizer will branch on that variable. The key DN implies that the mixed integer optimizer first will branch down on variable whereas the key UP implies that the mixed integer optimizer will first branch up on a variable.
If no branch direction is specified for a variable then the mixed integer optimizer will automatically choose the branching direction for that variable. Similarly, if no priority is assigned to a variable then it is automatically assigned the priority of 0.