[FRIAM] Optimization problem

[Steven A Smith]

Gary -

I *patently don't* recommend my method, though it does have some
charms.   I recently was faced with a similar problem to yours where I
needed to cut and install trim around the perimeter of the room (with
door openings) I just layed hardwood floor in.  

Rather than go into it in detail (I already did that and realized it was
a TL;DR as usual, so cut it) I will just say that I approach these
problems as *satisficing* and *constraint* problems rather than
*optimization*.    Once I had a candidate layout, I simply looked at the
results and determined that the *waste* was acceptable.   Depending on
the circumstances I sometimes prefer to have for example, 2 3' leftovers
rather than 1 5' leftover, other times, vice-versa, depending on how I
might use said leftovers in some future application (or hedging against
a mistake in my measuring/cutting).

Care to share what your actual conduit/pipe project is?

- Steve


> Thanks for the links, Peter. I will probably use that software or
> similar, to get a quick solution, then look at the MOOCs.
>
> On Fri, Sep 20, 2019 at 2:52 PM Pieter Steenekamp
> <pieters at randcontrols.co.za> wrote:
>> Two possible approaches are:
>> a) Solve the problem yourself. Use one or a combination of standard algorithms ( eg you mentioned linear programming and greedy algorithms, there are many more of course) and/or your own custom algorithm. If you wish to go this route and want to learn about the subject, I recommend the series of MOOCS by Stanford's Tim Roughgarden https://www.coursera.org/specializations/algorithms
>> Or, I think yours is probably a knapsack -type problem and the MOOC https://www.coursera.org/learn/discrete-optimization covers that relatively well.
>> b) But if you just want to get the solution you can use optimization software like https://www.ibm.com/za-en/products/ilog-cplex-optimization-studio (they have a free edition that will be good enough for your application) will solve it for you without you necessarily knowing how the software does it.
>>
>> On Fri, 20 Sep 2019 at 21:00, Gary Schiltz <gary at naturesvisualarts.com> wrote:
>>> I'd like advice on possible ways to solve the following problem
>>> (plumbers must surely face this all the time). I need to cut a set of
>>> metal tubes of varying lengths from standard length (6 meter)
>>> galvanized conduit stock. The goal is to find the number of tubes I
>>> need to buy, and the order of cuts to produce the minimum amount of
>>> leftover, unused tube.  I'm interested in what types of solutions
>>> people use for similar 1-dimensional problems, e.g. linear
>>> programming, greedy algorithms, etc. (I've been Googling). I'm only
>>> looking to cut around 15-25 pieces, so my gut feeling is that an
>>> exhaustive search of all possible solutions, though probably NP-hard,
>>> would be feasible to perform. Working programs, as well as libraries
>>> in any language would be a bonus.
>>>
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>> Meets Fridays 9a-11:30 at cafe at St. John's College
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> ============================================================
> FRIAM Applied Complexity Group listserv
> Meets Fridays 9a-11:30 at cafe at St. John's College
> to unsubscribe http://redfish.com/mailman/listinfo/friam_redfish.com
> archives back to 2003: http://friam.471366.n2.nabble.com/
> FRIAM-COMIC http://friam-comic.blogspot.com/ by Dr. Strangelove