Xypron, On Wed, Aug 13, 2008 at 2:34 AM, glpk xypron <[EMAIL PROTECTED]> wrote:
> Hello Vijay, > > in the example the optimization problem was to find the minimum number of > 6000 mm paper roles needed > to fulfill demand for > 4 * 2000 mm and > 4 * 1000 mm. > > The optimization result will be the same for any width of stock in the > interval [6000, 7000[ because the widths in demand cannot be combined to any > value in the interval ]6000, 7000[. > That's right. But just changing/adjusting maximum pattern width won't fix the problem. Would it? Right now I think accessing all integer optimal solutions of subproblem MIP will be fix the issue. You idea (below) of having fractional/adjusted value for maximum width could be still useful in solving this issue. Could you please have a look at detail explanation, here: http://code.google.com/p/cspsol/issues/detail?id=1#c7 Thanks > > Thus in the example the rounding errors could be avoided by using a paper > width of 6500 instead of 6000 in the optimization. > > Hence I propose to add a preprocessing step to cpsol to identify a > reasonable tolerance to add to the width of the stock. To determine the > tolerance I envision the following alternative solutions: > > 1) Identify the smallest combination of demand elements wider then the > width of the stock and the largest combination of demand elements equal or > smaller then the stock. Use the average as width of the stock in the > optimization. - This leaves You with problem to implement this step with > exact mathematics. > > 2) Limiting all input to integers simply add .5 times the greatest common > denominator (obviously at least .5) to the width of the stock. > > 3) Add a field for the rounding tolerance to the input file. > > Best regards > > Xypron > > -------- Original-Nachricht -------- > > Datum: Mon, 11 Aug 2008 23:32:08 +0530 > > Von: "Vijay Patil" <[EMAIL PROTECTED]> > > An: [email protected] > > Betreff: [Help-glpk] Irrational numbers > > > In one of application using GLPK, I am facing a problem because of not > > being > > able to represent irrational numbers/values correctly (as obj. func. > > coeff.). > > Actually these values are dual values and are obtained from glpk itself. > > Since they are approximated there is a problem (loss of information). > > > > If you have some experience/expertize dealing with irrational numbers or > > knowledge of floating point representation, you might be interested in > > having a look at the problem. > > > > http://code.google.com/p/cspsol/issues/detail?id=1#c2 > > > > Any workarounds to deal with this problem? > > > > Thanks > > -- > > Vijay Patil > > -- > Psssst! Schon das coole Video vom GMX MultiMessenger gesehen? > Der Eine für Alle: http://www.gmx.net/de/go/messenger03 > -- Vijay Patil
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