SCIP
Solving Constraint Integer Programs
Solving Constraint Integer Programs
methods to create a variable graph and perform breadth-first search
Functions | |
| SCIP_RETCODE | SCIPvariablegraphBreadthFirst (SCIP *scip, SCIP_VGRAPH *vargraph, SCIP_VAR **startvars, int nstartvars, int *distances, int maxdistance, int maxvars, int maxbinintvars) |
| SCIP_RETCODE | SCIPvariableGraphCreate (SCIP *scip, SCIP_VGRAPH **vargraph, SCIP_Bool relaxdenseconss, SCIP_Real relaxdensity, int *nrelaxedconstraints) |
| void | SCIPvariableGraphFree (SCIP *scip, SCIP_VGRAPH **vargraph) |
| SCIP_RETCODE SCIPvariablegraphBreadthFirst | ( | SCIP * | scip, |
| SCIP_VGRAPH * | vargraph, | ||
| SCIP_VAR ** | startvars, | ||
| int | nstartvars, | ||
| int * | distances, | ||
| int | maxdistance, | ||
| int | maxvars, | ||
| int | maxbinintvars | ||
| ) |
Perform breadth-first (BFS) search on the variable constraint graph.
The result of the algorithm is that the distances array contains the correct distances for every variable from the start variables. The distance of a variable can then be accessed through its problem index (calling SCIPvarGetProbindex()). Hence, The method assumes that the length of distances is at least SCIPgetNVars(). Variables that are not connected through constraints to the start variables have a distance of -1.
Limits can be provided to further restrict the breadth-first search. If a distance limit is given, the search will be performed until the first variable at this distance is popped from the queue, i.e., all variables with a distance < maxdistance have been labeled by the search. If a variable limit is given, the search stops after it completes the distance level at which the limit was reached. Hence, more variables may be actually labeled. The start variables are accounted for those variable limits.
If no variable variable constraint graph is provided, the method will create one and free it at the end This is useful for a single use of the variable constraint graph. For several consecutive uses, it is advised to create a variable constraint graph via SCIPvariableGraphCreate().
| scip | SCIP data structure |
| vargraph | pointer to the variable graph, or NULL to let the function create a local graph |
| startvars | array of start variables to calculate distance from |
| nstartvars | number of starting variables, at least 1 |
| distances | array to keep distance in vargraph from start variables for every variable |
| maxdistance | maximum distance >= 0 from start variable (INT_MAX for complete BFS) |
| maxvars | maximum number of variables to compute distance for |
| maxbinintvars | maximum number of binary or integer variables to compute distance for |
Definition at line 1435 of file heur.c.
References FALSE, SCIP_VGraph::nvarconss, SCIP_Bool, SCIP_CALL, SCIP_OKAY, SCIPallocBufferArray, SCIPallocClearBufferArray, SCIPfreeBufferArray, SCIPgetConsNVars(), SCIPgetConsVars(), SCIPgetVarsData(), SCIPhashtableExists(), SCIPhashtableInsert(), SCIPhashtableRemoveAll(), SCIPvarGetProbindex(), SCIPvariableGraphCreate(), SCIPvariableGraphFree(), SCIPvarIsActive(), TRUE, SCIP_VGraph::varconss, and SCIP_VGraph::visitedconss.
Referenced by alnsFixMoreVariables(), alnsUnfixVariables(), determineVariableFixings(), selectInitialVariable(), and selectNextVariable().
| SCIP_RETCODE SCIPvariableGraphCreate | ( | SCIP * | scip, |
| SCIP_VGRAPH ** | vargraph, | ||
| SCIP_Bool | relaxdenseconss, | ||
| SCIP_Real | relaxdensity, | ||
| int * | nrelaxedconstraints | ||
| ) |
initialization method of variable graph data structure
| scip | SCIP data structure |
| vargraph | pointer to the variable graph |
| relaxdenseconss | should dense constraints (at least as dense as density) be ignored by connectivity graph? |
| relaxdensity | density (with respect to number of variables) to relax constraint from graph |
| nrelaxedconstraints | pointer to store the number of constraints that were relaxed, or NULL if not needed |
Definition at line 1738 of file heur.c.
References fillVariableGraph(), SCIP_CALL, SCIP_OKAY, SCIPallocBlockMemory, SCIPallocClearBlockMemoryArray, SCIPblkmem(), SCIPgetNConss(), SCIPgetNVars(), and SCIPhashtableCreate().
Referenced by determineVariableFixings(), and SCIPvariablegraphBreadthFirst().
| void SCIPvariableGraphFree | ( | SCIP * | scip, |
| SCIP_VGRAPH ** | vargraph | ||
| ) |
deinitialization method of variable graph data structure
| scip | SCIP data structure |
| vargraph | pointer to the variable graph |
Definition at line 1776 of file heur.c.
References SCIPfreeBlockMemory, SCIPfreeBlockMemoryArray, SCIPfreeBlockMemoryArrayNull, SCIPgetNVars(), and SCIPhashtableFree().
Referenced by determineVariableFixings(), and SCIPvariablegraphBreadthFirst().