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

[Drescher, Conrad]

Hi Christian,

thanks a lot, that looks very good! For us, I don't see a use case for stronger reified variants...

Best wishes,
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
www.sap.com<http://www.sap.com/>

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From: Christian Schulte [mailto:cschulte at kth.se]
Sent: Montag, 13. März 2017 13:08
To: Drescher, Conrad <conrad.drescher at sap.com>; users at gecode.org
Subject: RE: [gecode-users] Question on IntVar-equalities with and without MiniModel

Hi Conrad,

I just had a look at the code and the second option seems to be quite easy to do. The candidates for domain consistent propagation would be:

-          x = y, x = -y

-          x + y = c, x - y = c (provided that x, y, c do not exceed some limit)

However, getting also the reified variants domain consistent would require some (not much) work. Would that be needed as well?

Cheers
Christian

--
Christian Schulte, www.gecode.org/~schulte<http://www.gecode.org/~schulte>
Professor of Computer Science, KTH, cschulte at kth.se<mailto:cschulte at kth.se>
Expert Researcher, RISE SICS, christian.schulte at ri.se<mailto:christian.schulte at ri.se>

From: Drescher, Conrad [mailto:conrad.drescher at sap.com]
Sent: Monday, March 13, 2017 10:22
To: users at gecode.org<mailto:users at gecode.org>
Cc: cschulte at kth.se<mailto:cschulte at kth.se>
Subject: RE: [gecode-users] Question on IntVar-equalities with and without MiniModel

Hi Christian,

I had not even thought of the first option... the second option should be easily sufficient for our purposes. If it were possible to make that special case of "x == y" behave like "x IRT_EQ y" that would really benefit our use case. We have no interest in using DOM for the general case of "IntExpr1 == IntExpr2".

Many thanks for considering the idea, and the great software in general!
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<mailto:conrad.drescher at sap.com>
www.sap.com<http://www.sap.com/>

Please consider the impact on the environment before printing this e-mail.


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From: Christian Schulte [mailto:cschulte at kth.se]
Sent: Montag, 13. März 2017 09:41
To: Drescher, Conrad <conrad.drescher at sap.com<mailto:conrad.drescher at sap.com>>; users at gecode.org<mailto:users at gecode.org>
Subject: RE: [gecode-users] Question on IntVar-equalities with and without MiniModel

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<http://www.gecode.org/~schulte>
Professor of Computer Science, KTH, cschulte at kth.se<mailto:cschulte at kth.se>
Expert Researcher, RISE ICT/SICS, cschulte at sics.se<mailto:cschulte at sics.se>

From: users-bounces at gecode.org<mailto: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<mailto: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<mailto:conrad.drescher at sap.com>
www.sap.com<http://www.sap.com/>

Please consider the impact on the environment before printing this e-mail.


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