AlgorithmOverview(3)

NAME
AlgorithmOverview - Description of the algorithm.

SYNOPSIS

Detailed Description

Description of the algorithm. The algorithm top-level is implemented in the NegociateWindow.

First step : NegociateWindow::_loadRouting()
1.  Load routing wires (AutoSegment) from KatabaticEngine inside the Kite GCell's. Then update the GCell's density.
2.  Sort the GCell's according to decreasing density (denser GCell's are to be routed first).
3.  Agglomerate clusters of contiguous GCell's whose density is superior to 0.7 to the seed GCell. See GCellRoutingSet for the mechanism.
GCellRoutingSet receive an increasing order number. The higher the order the lower the density. This order is transmitted to the TrackSegment of the GCellRoutingSet to be taken into account by the track cost function.
Second step : NegociateWindow::_runOnGCellRoutingSet()
For each GCellRoutingSet in decreasing density, negociate the set of associated TrackSegment.
1.  Build a RoutingEventQueue from the list of TrackSegment. The queue is responsible for allocating the RoutingEvent associated to each TrackSegment.
2.  The queue is sorted according to the 'event level' then to the priority, which is for now the slack of the TrackSegment. That is, constrained TrackSegment are routed first.
3.  The queue is processed till it's empty (no unprocessed RoutingEvent remains).
Processing a RoutingEvent is trying to insert a TrackSegment in a suitable Track. We proceed as follow :
•   The maximum ripup count for the to be inserted segment has been reached. Issue a severe warning and left unrouted this TrackSegment (for now).
•   Compute the Tracks in which the TrackSegment can be inserted, then compute the insertion cost in each one. The candidates are ordered by the insertion cost.
•   Now consider the lower cost Track. If there is a free interval for the TrackSegment. Issue a Session::addInsertEvent() then finish.
If there is a 'soft overlap', that is the overlaping TrackSegment already in the Track could be shrunk either to the left or the right so the new TrackSegment can be inserted. This is managed by RoutingEvent::_setAside(), for each soft overlaping TrackSegment, gets its perpandiculars and issue a displacement request for all of them. That is, re-post a RoutingEvent with updated constraints and remove the perpandicular from it's Track if it has already been routed. Note that no request is issued for the overlaping TrackSegment itself has it do not change of Track.
If there is a 'hard overlap', that is the two TrackSegment cannot share the same Track, remove the previous one from the Track and re-post a RoutingEvent. Note that, the cost object should have selected a TrackSegment which could be ripped-up. Otherwise the Track would'nt even be a candidate.
When a TrackSegment is riped up, it is re-routed immediately afterward. This is done by increasing his event level.

Author
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