[gecode-users] Question on IntVar-equalities with and without MiniModel

[Christian Schulte]

Hmmm, not that straightforward. There are two ideas here:

-          One idea would be that there is an additional IPL (integer
propagation level) called something like IPL_CHEAP_DOM which does domain
propagation only if it is cheap.

-          The other idea would be that linear interprets the default IPL
ILP_DEF differently: normally it uses IPL_BND but for special cases it uses
IPL_DOM.

 

The second might be easier to pull off


 

Cheers

Christian

 

--

Christian Schulte, www.gecode.org/~schulte

Professor of Computer Science, KTH,  <mailto:cschulte at kth.se>
cschulte at kth.se

Expert Researcher, RISE ICT/SICS,  <mailto:cschulte at sics.se>
cschulte at sics.se

 

From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On Behalf
Of Drescher, Conrad
Sent: Friday, March 10, 2017 09:47
To: users at gecode.org
Subject: [gecode-users] Question on IntVar-equalities with and without
MiniModel

 

Hi there,

 

I have a question on the „equal“ constraint between two IntVars, let’s say
x0 with domain [1,3,5], and x1 with domain
[Int::Limits::min..Int::Limits::max].

 

If I write rel(home,x0,IRT_EQ,x1); x1 gets restricted to [1,3,5] as IRT_EQs
default propagation level is IPL_DOM. But if I write rel(home,x0 == x1);
using MiniModel x1 gets restricted to [1 – 5].

 

Apparently equalities between linear integer expressions get summarized into
a “linear” constraint in MiniModel, which of course is nice. This linear
constraint in turn seems to have a lot of special cases covered (which I
haven’t fully grasped yet). But I wonder whether it’d be possible to get the
case of there being just two variables back up to IPL_DOM instead of
IPL_BND? Of course, I understand you wouldn’t want to have IPL_DOM for
linear in general


 

Many thanks!

Conrad

 

Dr. Conrad Drescher

Senior Developer | Variant Configuration
P&I S/4HANA Idea – LoB Research & Development

SAP SE | Dietmar-Hopp-Allee 16 | 69190 Walldorf | Germany

T +49 6227 7-77888 | M +49 160 90684883 | E conrad.drescher at sap.com
 <http://www.sap.com/> www.sap.com


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