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<p class="MsoNormal"><span style="color:#1F497D">Geoffrey, <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Thanks, this was very helpful.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">--Bill<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"> rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org]
<b>On Behalf Of </b>Geoffrey De Smet<br>
<b>Sent:</b> Friday, October 12, 2012 11:11 AM<br>
<b>To:</b> Rules Users List<br>
<b>Subject:</b> Re: [rules-users] Drools Planner for purchasing optimization - good fit for problem?<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Op 11-10-12 21:34, Schneider, Bill schreef:<o:p></o:p></p>
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<p class="MsoNormal"><span style="color:#1F497D">Geoffrey, </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Thanks for the quick response. </span>
<o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">As I’m learning more about my scenario, it feels more like a mixed-integer problem than a combinatorial problem. The objective function is linear in the decision variables. I would model the decision variables
as the quantities of each item from each vendor. </span><o:p></o:p></p>
</blockquote>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">This might be the biggest hurdle in Planner. A variable that represents a quantity, for which is it's unrealistic to make a pool of all values is currently difficult (but
not impossible) in Planner. Future work will improve support for this - but currently you 'll likely need to implement custom moves (see manual).<br>
<br>
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">The conditional offers I could model as a separate vendor/bid, with a binary decision variable for “condition met?” and inequalities to constrain the quantities that depend on the binary variable. Some of the
global constraints can be modeled in the same way, like “at most two vendors.”</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">It sounds like there are some advantages to using Drools Planner in terms of readability and maintainability of the relationships and constraints – you have the full expressive power of DRL (or Java), and are
not limited to inequalities. That could make it easier to program for new types of rules or constraints later.
</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Are there any advantages to using Drools Planner from a computational-complexity standpoint as well? Would it *<b>hurt</b>* to use in terms of CPU/memory, or even learning curve, for a problem that is possibly
not combinatorial, and might be solvable with other means?</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">In my experience, if it scales beyond 10 000 values (= bids) and 10 000 purchases, LP and MIP's memory requirements are impossible today and metaheuristics are the only
way.<br>
See Google roadef 2012 competition: <a href="http://blog.athico.com/2012/06/roadef-2012-first-results-for-dataset-b.html">
http://blog.athico.com/2012/06/roadef-2012-first-results-for-dataset-b.html</a><br>
And that's even without scaling out the number of constraints (= score rules).<br>
<br>
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Also – are you aware of any case studies or examples of Drools Planner being used in the purchasing domain like this?
</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman","serif"">Not in the purchasing domain - I suspect the quantity complexity is hindering adoption in that area currently.<br>
<br>
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Thanks again!</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">--Bill</span><o:p></o:p></p>
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