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

[Stephen V. Mather]

It would be easier to create new points rather than modifying the returned route?

I'll take a look at the repo link.
Thanks!
Best,
Steve


[http://sig.cmparks.net/cmp-ms-90x122.png] Stephen V. Mather
GIS Manager
(216) 635-3243 (Work)
clevelandmetroparks.com<http://www.clemetparks.com>



________________________________
From: pgrouting-users-bounces at lists.osgeo.org [pgrouting-users-bounces at lists.osgeo.org] on behalf of Daniel Kastl [daniel at georepublic.de]
Sent: Friday, April 12, 2013 11:16 PM
To: pgRouting users mailing list
Subject: Re: [pgrouting-users] A* vs. Dijkstra and the nature of the A* implementation



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<mailto:daniel.kastl at georepublic.de>
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