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<div class="moz-cite-prefix">Op 11-10-12 16:19, Schneider, Bill
schreef:<br>
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<p class="MsoPlainText">I'm trying to understand whether Drools
Planner is a good fit for a purchasing optimization problem.
<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">The problem is something like this:
there are X different items, each of which can be purchased
from Y different vendors at different prices. The objective
variable/function to minimize is the total amount purchased
(sum(qty_i * price_i)).<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">Some vendor prices are conditional -
only valid if you purchase more than some minimum threshold,
or if you purchase more than some total quantity from that
vendor. There are some additional constraints like
dual-sourcing<o:p></o:p></p>
<p class="MsoPlainText">- for some item x_i, exactly two vendors
must be selected.
<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">I feel like you *could* probably solve
this problem in Drools Planner,</p>
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Yes<br>
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<p class="MsoPlainText"> but I'm not sure if it's the best way,
or if a more traditional solver approach would be better. It
feels more like a linear programming problem at its core, and
I'm having a hard time figuring out where the boundary is -
what kind of constraint would make the problem "non-convex" or
"non-smooth" to the point where a local search (tabu,
evolutionary etc.) is required?</p>
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That's hard to tell from this distance.<br>
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- If you want to upscale, go Metaheuristics (for example with
Planner). If you want to downscale, linear programming might be a
better fit. (Compo's like ROADEF 2012 assert this statement).<br>
- LP will require you to write your constraints as mathematical
equitations based on arrays and primitives, for example "x < y *
1.21". Planner uses a declarative OO approach using drools rules (or
even just plain Java), for example "Invoice ($x < yWithVAT)".<br>
- If you have different conditional price types, you might want to
look into using a drools decision table to easily declare that
conditional logic - and use that as in Planner. Especially if those
rules change often.<br>
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<p class="MsoPlainText"><o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">Thanks for any help you can give.<o:p></o:p></p>
<p class="MsoPlainText">--Bill<o:p></o:p></p>
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