[TRNSPRTPCE-147] k shortest paths with include constraint

Fri, 13 Mar 2020 14:25:25 +0000

In the runKgraphs() method in PceGraph.java there is the following code:

// local optimization. if 'include' constraint exists then increase amount of paths to return.
// it's because this constraint is checked at the last step when part of good paths
// are dropped by other constraints
if (!pceHardConstraints.getListToInclude().isEmpty()) {
    kpathsToBring = kpathsToBring * 10;
    LOG.info("k = {}",kpathsToBring);
}

So the number of paths to be returned by the k shortest paths algorithm is increased by a factor 10 when there are include constraints. It is not clear to me why this is needed. From the jgrapht documentation it seems to me that the KShortestSimplePaths.getPaths method returns k paths fulfilling the constraints if such paths exist (i.e. it's not that it first calculates k paths and then removes some of them that doesn't fulfill the constraints) so why increase k in this case? Have I misunderstood the implementation?

OpenDaylight JIRA

[TRNSPRTPCE-147] k shortest paths with include constraint