[pgrouting-users] A* vs. Dijkstra and the nature of the A* implementation

[Daniel Kastl]

>
>  For datasets as large as the one we are working with, this seems to
>> result in a pretty high random IO tax.  I wondered if anyone has some
>> boilerplate modifying the returned route, slicing the nearest ways to
>> the beginning and end points with ST_ClosestPoint or similar?
>>
>
> I have done this, it is not that hard.
>
>
As Steve said, this is not so hard. You can select the closest point on the
nearest road segment and PostGIS has all the function to gibe you a
substring from that point.
There is an example how to do this with Shooting Star, which has some
problems at the moment, but just to get an idea:
https://github.com/pgRouting/pgrouting/blob/sew-devel-2_0/src/common/sql/pgrouting_network_check.sql
Shooting Star routes from road segment to road segment, so the logic is
slightly different. For other algorithms such as TRSP you probably need to
create a temporary node.
So in short, I wouldn't modify the returned route but start from new points.

Daniel


-- 
Georepublic UG & Georepublic Japan
eMail: daniel.kastl at georepublic.de
Web: http://georepublic.de
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