From: Joachim Schimpf <joachim.schimpf_at_infotech.monash.edu.au>

Date: Tue, 03 Nov 2009 11:00:08 +1100

Date: Tue, 03 Nov 2009 11:00:08 +1100

Igor Kondrasovas wrote: > I have a preliminary version of my program running, but one important > thing missing is that I need to dynamically impose the constraints, > based on the length of the input arrays. Let me show an example with > what I mean: > > linear(PieceLengths, BarsLengths, M) :- > dim(PieceLengths, [NPieces]), > dim(BarsLengths, [NBars]), > dim(M,[NPieces,NBars]), > M #::0..1, > > % Constraints that the sum of every column value in each row must be equals 1 > M[1,1] + M[1,2] + M[1,3] #= 1, > M[2,1] + M[2,2] + M[2,3] #= 1, > M[3,1] + M[3,2] + M[3,3] #= 1, > M[4,1] + M[4,2] + M[4,3] #= 1, > M[5,1] + M[5,2] + M[5,3] #= 1, > M[6,1] + M[6,2] + M[6,3] #= 1, > M[7,1] + M[7,2] + M[7,3] #= 1, > M[8,1] + M[8,2] + M[8,3] #= 1, > M[9,1] + M[9,2] + M[9,3] #= 1, > M[10,1] + M[10,2] + M[10,3] #= 1, > > As you can see here, this constrains are fixed and will work only when M > is 10x3 matrix. I must change it in order to accept any input > configuration. > > I imagine I can iterate to every single line of the M matrix using a > simple for loop. But for the sum of the columns values a loop will not > help me since I must âconstructâ the constraint instead of perform any > calculation at every iteration. Is it possible to do with Eclipse? Yes, ECLiPSe is very good at symbolic manipulation, e.g. you could write LeftHandSide = M[1,1] + M[1,2] + M[1,3], LeftHandSide #= 1. Here, LeftHandSide contains the symbolic expression _as_a_data_structure_, and you can use that in the #= constraint. You can then of course construct such a data structure in a loop: ( for(J,1,3), fromto(0,LHS1,LHS2,LHS), param(M) do LHS2 = LHS1 + M[1,J] ), LHS #= 1. A little bit simpler is to construct a list and use sum(List): ( for(J,1,3), foreach(M[1,J],MIJs), param(M) do true ), sum(MIJs) #= 1. And even simpler is the following shorthand: sum(M[1,1..3]) #= 1. Have a look at some examples on the web site http://eclipse-clp.org/examples/magicsquare.ecl.txt or http://eclipse-clp.org/examples/tomo.ecl.txt -- JoachimReceived on Tue Nov 03 2009 - 00:00:09 CET

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