[gecode-users] A problem for restart

[Zhu Zichen's cse]

Dear all,

       Well, it seems that change "return true" into "return false" means
that we do not restart when a solution is found. While the "if" condition
is only do not post that no-good when a solution is found.

Zichen

On Tue, Dec 16, 2014 at 11:31 PM, Zhu Zichen's cse <zzhu at cse.cuhk.edu.hk>
wrote:
>
> Dear Christian,
>
> Oh, that's another problem. I redefine the master() function as described
> at page 161,
> if (cri.solution() == 0 )
>      cri.nogoods().post(*this)
> so that do not restart if a solution is found. The infinite loop still
> there. The only way to stop it is to "return false" rather than "return
> true".
>
> It seems the "if" condition is not useful. I am really confused about that.
>
> Zichen
>
> On Tue, Dec 16, 2014 at 11:22 PM, Christian Schulte <cschulte at kth.se>
> wrote:
>
>> Hmmmm, I had a look and that should work. I will look into a little later
>> (after Christmas).
>>
>>
>>
>> However: it will work when you do not restart on a solution. Then, the
>> combination of all solution search together with restarts is not really
>> that meaningful, is it?
>>
>>
>>
>> Cheers
>>
>> Christian
>>
>>
>>
>> --
>>
>> Christian Schulte, Professor of Computer Science, KTH,
>> www.gecode.org/~schulte/
>>
>>
>>
>> *From:* zichenzu at gmail.com [mailto:zichenzu at gmail.com] *On Behalf Of *Zhu
>> Zichen's cse
>> *Sent:* Tuesday, December 16, 2014 4:14 PM
>> *To:* cschulte at kth.se
>> *Cc:* users at gecode.org
>> *Subject:* Re: [gecode-users] A problem for restart
>>
>>
>>
>> Dear Christian,
>>
>>
>>
>>      Here are the codes. Many thanks.
>>
>>
>>
>> Zichen
>>
>>
>>
>> On Tue, Dec 16, 2014 at 11:04 PM, Christian Schulte <cschulte at kth.se>
>> wrote:
>>
>> Hi Zichen,
>>
>>
>>
>> MPG does not make a promise here: it says "the solution might not be
>> found again" but it does not give you a guarantee. But for your example I
>> would have to know how nqueen_rbs looks like.
>>
>>
>>
>> Cheers
>>
>> Christian
>>
>>
>>
>> --
>>
>> Christian Schulte, Professor of Computer Science, KTH,
>> www.gecode.org/~schulte/
>>
>>
>>
>> *From:* users-bounces at gecode.org [mailto:users-bounces at gecode.org] *On
>> Behalf Of *Zhu Zichen's cse
>> *Sent:* Tuesday, December 16, 2014 3:43 PM
>> *To:* users at gecode.org
>> *Subject:* [gecode-users] A problem for restart
>>
>>
>>
>> Dear all,
>>
>>
>>
>> I met a problem when using ​restart in Gecode.
>>
>>
>>
>> I simply use restart to find all solutions for 4-Queens while use the
>> same heuristic after each restart:
>>
>> ./nqueen_rbs -restart geometric -restart-scale 2 -restart-base 10
>> -nogoods 1 -nogoods-limit 128 4
>>
>>
>>
>> But I got into an infinite loop which keeps printing the first solution.
>>
>>
>>
>> According to the newest version of document "MPG" (page 160), the
>> master() function posts no-goods when the a solution is found. This means
>> the same solution will not be found again.
>>
>>
>>
>> I rewrite the master() function by changing the last line "return true"
>> into "return false", now all solutions are generated without trapped into a
>> loop.
>>
>>
>>
>> I am wondering why the infinite loop happens and whether Gecode has truly
>> recorded previous solutions as nogoods as the document says.
>>
>>
>>
>> Thanks for help.
>>
>>
>>
>> Zichen
>>
>> [image: Image removed by sender.]
>>
>>
>>
>
>
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