[gecode-users] Problem to formulate a constraint

[Uwe Nowak]

Hi!

Sorry for spamming the mailing list...
At the moment I am focussing on the 3rd ide of modelling.
Then I have to formulate constraints as

c=j <==> x_{j+u} = v

By substituting i=j-u I get

c=i+u <==> x_i = v

Which looks pretty much like the channel constraint, except that on the right side there is x_i = v instead of x_i = 1.
Do I need additional (temporary) boolean variables to get rid of this?

Best Regards,
Uwe Nowak

 
----------------ursprüngliche Nachricht-----------------
Von: "Uwe Nowak" uwe.nowak at itwm.fraunhofer.de 
An: users at gecode.org 
Datum: Sat, 25 May 2013 23:33:18 +0200
-------------------------------------------------
 
 
> Hi!
> 
> Thank you for your answer. As I stated, I am a beginner to gecode and constraint 
> programming at all. I did not
> try reification, but by this keyword I managed to solve the problem.
> 
> 
> 
> However, I still think, that I am formulating my constraint in a bad way. I managed 
> to reduce my
> (sub)problem to the following:
> 
> I have an one-dimensional array
> #############
> 
> Furthermore, I have patterns such as
> Pattern 1 = aa#a
> Pattern 2 = b#b#b
> where the hash means an empty field. 
> 
> I want to place these patterns on the array, i.e. possible placements are
> Placement 1: aa#a###b#b#b#
> Placement 2: aabab#b######
> 
> No I want to store the position (i.e. the column) of each pattern in an IntVarArray 
> c, i.e. in Placement 1 it
> is c=(0; 7) in Placement 2 it is c=(0; 2). However I do not know, how to formulate the 
> non-overlapping.
> 
> 
> I have three possible Ideas:
> 1. For each pattern I have an BoolVarArray to indicate if the pattern is placed 
> there
> For Placement 1 I have two arrays (for pattern 1 = 1101000000000) and (for Pattern 
> 2 = 0000000101010)
> Then I have constraints
> c_a=j <==> x_{j+0} = x_{j+1} = x_{j+3} = 1
> c_b=j <==> y_{j+0} = y_{j+2} = y_{j+4} = 1
> 
> 
> 2. I have one IntVarArray that stores the pattern placed at this field.
> For Placement 1 this is 1101000202020
> Then I have constraints
> c_a=j <==> x_{j+0} = x_{j+1} = x_{j+3} = 1
> c_b=j <==> x_{j+0} = x_{j+2} = x_{j+4} = 2
> 
> 
> 3. I assign different numbers to each point of the the pattern, I.e. pattern 1 = 
> 12#3 and Pattern 2=4#5#6
> For Placement 1 this is 1203000405060
> Then I have constraints
> c_a=j <==> x_{j+0} = 1 
> c_a=j <==> x_{j+1} = 2 
> c_a=j <==> x_{j+3} = 3
> c_b=j <==> x_{j+0} = 4 
> c_b=j <==> x_{j+2} = 5 
> c_b=j <==> x_{j+4} = 6
> 
> However I am somehow lost, how to formulate such constraints efficiently.
> Although this seems a little bit similar to the Pentomino example, with my 
> current gecode-skills I am not
> able to transfer the Ideas.
> 
> Best Regards,
> Uwe
> 
> 
> ----------------ursprüngliche Nachricht-----------------
> Von: "Christian Schulte" cschulte at kth.se 
> An: "'Uwe Nowak'" uwe.nowak at itwm.fraunhofer.de , users at gecode.org 
> Datum: Thu, 23 May 2013 17:49:07 +0200
> -------------------------------------------------
> 
> 
>> Hi,
>> 
>> Did you try reification? While not great, it should not be too hard to pull
>> this off. Or am I missing something here?
>> 
>> Best
>> Christian
>> 
>> --
>> Christian Schulte, Professor of Computer Science, KTH,
>> www.ict.kth.se/~cschulte/
>> 
>> 
>> -----Original Message-----
>> From: users-bounces at gecode.org [mailto:users-bounces at gecode.org ] On
>> Behalf
>> Of Uwe Nowak
>> Sent: Thursday, May 23, 2013 3:40 PM
>> To: users at gecode.org 
>> Subject: [gecode-users] Problem to formulate a constraint
>> 
>> I am a beginner with gecode and have a problem to formulate a constraint.
>> I was looking through all channel constraints, however they do not seem to
>> fit my needs, or I am unable to formulate my needs in the language of the
>> channel constraints.
>> 
>> I have the following variables
>> *an IntVar c with a finite set of values {A_1,...,A_n} *an IntVarArray p
>> 
>> I have the following fixed parameters
>> For each value A_t I have a finite set of fixed indexed values I_t (e.g, an
>> std::set<int>)
>> A constant B
>> 
>> Now I want to formulate the following constraints for(t = 1...n){
>> 	c=A_t ==> for all I in I_t: p[i]=B
>> }
>> 
>> 
>> I thought to create an IntVarArgs of the subset of p with the indices I_t
>> However, than I have tor formulated for an IntVarArgs q_t:
>> for(t = 1...n){
>> 	c=A_t ==> For all elements q_t[i]=B
>> }
>> 
>> However, I do not find the right expressions to formulate this in gecode...
>> 
>> 
>> 
>> _______________________________________________
>> Gecode users mailing list
>> users at gecode.org 
>> https://www.gecode.org/mailman/listinfo/gecode-users
>> 
>> 
> 
> 
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