[pgrouting-users] pgr_apspjohnson algorithm

[Stephen Woodbridge]

On 1/5/2014 2:16 PM, Helder Alves wrote:
> Hi Daniel,
>
> Regarding pgr_apspjohnson, I came to the conclusion that SQL query
> passed into pgr_apspjohnson must already return a shortest path distance
> matrix including all the stop points we want to optimize. Am I getting
> it right?
>
> What I'm about to try now is to unnest the distance matrix generated for
> pgr_TSP to feed pgr_apspjohnson...

You might be able to use something like this to convert the distance 
matrix into a table:

with dm as (
   select '{{1,2,3,4,5},
            {6,7,8,9,10},
            {11,12,13,14,15},
            {16,17,18,19,20},
            {21,22,23,24,25}}'::int[] as dm
)
select i, j, dm.dm[j][i]
   from generate_series(1, 5) i,
        generate_series(1, 5) j,
        dm;

-Steve

> Problem was that from all my previous reading I thought that at some
> point APSP Johnson would itself generate the routing graphs, what seems
> not to be the case, if my understanding from the source code is right...
> Meaning APSP Johnson only takes care of the total route minimum cost
> (permutations) avoiding the problem of TSP with negative costs.
>
> Please let me know if I made foolish assumptions! :-)
>
> --
> Helder Alves
>
>
>
>
>
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