[pgrouting-users] Strange results using pgr_kdijkstraCost

[António M. Rodrigues]

Hi all,

I'm using osm data to calculate time distances from one source node to
multiple destinations. For this I'm using pgr_kdijkstraCost. Because I
found a few results strange, I used pgr_dijkstra (and pgr_astar) to test
total distances between a few nodes.

Given one source and one destination, I used this code to calculate total
cost between two nodes

-----test1
select sum(cost) from
(SELECT seq, id1 AS node, id2 AS edge, cost FROM pgr_dijkstra('
                SELECT gid AS id,
                         source::integer,
                         target::integer,
                         length::double precision AS cost
                        FROM ways',
                97972,342392, false, false)) as foo;

----------
*column "custo" was calculated using: custo = (60 * length) /
(maxspeed_forward)

The result for test1 is 115 minutes.

----------

Using pgr_kdijkstraCost with only one target (node 342392), the code is:

-----test2
SELECT seq, id1 AS source, id2 AS target, cost FROM pgr_kdijkstraCost($$
                SELECT gid AS id,
                         source::integer,
                         target::integer,
                         custo::double precision AS cost
                        FROM ways, classes c
                        WHERE class_id = c.id
                         $$,
                97972, array[342392], false, false);
----------
The result of test2 is 66388 minutes!

Using the same code with over 2 thousand targets, it runs smoothly, with a
few strange results - as this one.

------------------------------------------------------------------

Perhaps there's something obvious I'm missing.

Thanks in advance for any help.
António
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