[FRIAM] Optimization problem

[Marcus Daniels]

In my experience, general purpose constraint and SMT solvers tend to have poor performance compared to linear relaxation techniques found in mathematical optimization products like CPLEX (which also have constraints but from a limited repertoire).   It depends on the nature of your constraints whether CPLEX will work, but I think it will for your problem.  

On 9/20/19, 3:55 PM, "Friam on behalf of Steven A Smith" <friam-bounces at redfish.com on behalf of sasmyth at swcp.com> wrote:

    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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