Originally posted by: DouglasC

Hi

Can anybody tell me what the difference is between the following two constraints (note the only difference is the placement of the forall)?

validFixturePitch =
forall(i in set_fixtures) sum(k in set_pitches) sum(j in set_timeslots)
Fixs[i][j][k] * FixturePitch[i][k] == 1;
forall(i in set_fixtures)
validFixturePitch[i] =
sum(k in set_pitches) sum(j in set_timeslots)
Fixs[i][j][k] * FixturePitch[i][k] == 1;
For the constraint I am modelling they seem to do the same thing, but when I have tested on other constraints, they seem to be different.

As well as an English description, the relevant LP "s.t." would be useful.

Thanks

Doug
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Originally posted by: Ed Chamberlayne

The first validFixturePitch is missing the "[i]". If you added it, I assume you would get an error and would have to move the forall statement before it as you have done in the second example.
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Originally posted by: DouglasC

Thanks. You are right in what you say but it does not really answer my queery.

Both statements work and produce the same answer so are they the SAME thing, just expressed differently?

I don't think so, as I have tried other constratints where using the two formulations leads to dofferent results - but I'd be interested to know if people belive that they should be the same and the two formulations are interchangeable.

Thanks again

Doug
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Originally posted by: DouglasC

I have also posted this on "OPL Optimizer" list (https://www.ibm.com/developerworks/forums/thread.jspa?threadID=341558&tstart=0). I don't want to flame the lists but I think that it might be a better forum.
I will update both lists with any responses.
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