The Directives (.dir) File
This consists of an unordered sequence of records which specify branching priorities, forced branching directions and pseudo costs, read into the Optimizer using the XPRSreaddirs (READDIRS) command. By default its name is of the form problem_name.dir.
Directive file records have the format:
| Col 2-3 | Col 5-12 | Col 25-36 |
| type | entity | value |
type is one of:
| PR | implying a priority entry (the value gives the priority, which must be an integer between 0 and 1000. Values greater than 1000 are rejected, and real values are rounded down to the next integer. A low value means that the entity is more likely to be selected for branching.) |
| UP | the entity is to be forced up (value is not used) |
| DN | the entity is to be forced down (value is not used) |
| PU | an up pseudo cost entry (the value gives the cost) |
| PD | a down pseudo cost entry (the value gives the cost) |
| MC | a model cut entry (value is not used) |
| DR | a delayed row entry (value is not used) |
| BR | force the optimizer to branch on the entity even if it is satisfied. If a node solution is global feasible, the optimizer will first branch on any branchable entity flagged with BR before returning the solution. |
entity is the name of a global entity (vector or special ordered set), or a mask. A mask may comprise ordinary characters which match the given character: a ? which matches any single character, or a *, which matches any string or characters. A * can only appear at the end of a mask.
value is the value to accompany the type.
For example:
| PR x1* 2 |
gives global entities (integer variables etc.) whose names start with x1 a priority of 2. Note that the use of a mask: a * matches all possible strings after the initial x1.
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