Use of Portfolio

[marcus...@gmail.com]

Hello,

I'm using a Portfolio with two DFSs each having a branching strategy.
I thought these 2 DFS were going to share the search tree but I see that
I find duplicate solutions and the number of fails is equal to the number of fails of the two DSFs.

Is it normal ?  I apparently misunderstood the use case of Portfolios...

How to switch between two search strategies within the same resolution tree ?

Thank you,

Marcus

[Mikael Zayenz Lagerkvist]

Hi,

The search engines in the portfolio search have fully independent
search trees, which is intended. It is typically mostly used for cases
for either first-solution search or for optimizing search, not for all
solution search.

If you use a restarting-search, you can add no-goods (see Section 9.6
in MPG) to filter out previously visited parts. This will remove some
of the duplicate search, but also comes at a cost. Always worth
exploring.

You can also use branch and bound-style search to filter out
previously found solutions by adding the requirement that any new
solution is different than the most recent one found. However, it is
fundamentally impossible to avoid a situation where two assets in the
portfolio find the exact same solution at the same time, so you might
need to handle this outside the search.

Cheers;
Mikael

> --
> You received this message because you are subscribed to the Google Groups "Gecode" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to gecode+un...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/gecode/8f93505d-e8f0-4c8f-9150-7ac9c4c259cfn%40googlegroups.com.



--
Mikael Zayenz Lagerkvist

[Marcus Vilain]

Hi,

Great thanks for your answer. I will try to use RBS. I also wondered why a sequential portfolio did not use the number of cutoffs of each search Stop Options but rather a common number (slice) (MPG 6.2.0 page 172) 

In a sequential portfolio, is it possible to switch from one engine to another by specifying for each a given number of authorized failures ?

Cheers,

Marcus 

To view this discussion on the web visit https://groups.google.com/d/msgid/gecode/CAPKxCj5K_ZdR1TyLRAq%2BW4xy2W92%2BH2CCL1Qqt5UVL85oWOgfA%40mail.gmail.com.