[gecode-users] A problem for restart

[Christian Schulte]

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

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