About transportation problem
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From: Konstantin Smirnov on 9 Feb 2010 15:24 Is transportation problem generally solved, so there are no big problems to solve it now? For ex., if some data are subdetermined (lie in some interval [a,b]), is it also difficult to solve them with modern methods? Can someone give a system of constraints (Constraint satisfaction problem) related to transportation problem which is difficult to solve?
From: Robert Israel on 9 Feb 2010 19:57 Konstantin Smirnov <konstantin.e.smirnov(a)gmail.com> writes: > Is transportation problem generally solved, so there are no big > problems to solve it now? For ex., if some data are subdetermined (lie > in some interval [a,b]), is it also difficult to solve them with > modern methods? More generally, there are quite efficient polynomial-time algorithms for linear "network flow" problems, so in principle (and to a great extent in practice) these are all "easy". > Can someone give a system of constraints (Constraint satisfaction > problem) related to transportation problem which is difficult to solve? Make it nonlinear, e.g. a quadratic assignment problem. -- Robert Israel israel(a)math.MyUniversitysInitials.ca Department of Mathematics http://www.math.ubc.ca/~israel University of British Columbia Vancouver, BC, Canada
From: Ray Vickson on 9 Feb 2010 22:13 On Feb 9, 12:24 pm, Konstantin Smirnov <konstantin.e.smir...(a)gmail.com> wrote: > Is transportation problem generally solved, so there are no big > problems to solve it now? For ex., if some data are subdetermined (lie > in some interval [a,b]), is it also difficult to solve them with > modern methods? Google 'robust optimization'. R.G. Vickson > Can someone give a system of constraints (Constraint satisfaction > problem) related to transportation problem which is difficult to solve?
From: spudnik on 9 Feb 2010 22:23 I am physically \, psychically & legally restained from googoling any thing; how about "travellin' salesman on a globe?" > Google 'robust optimization'. thus: could you supply a "sixth grade math / sixth grade english" explanation of the "removal of pi?" thank you! > <http://www.ams.org/proc/2003-131-07/S0002-9939-02-06753-9/S0002-9939-...>. thus: aether; may not mean what y'think it be!... quantum foam, either. redshift, assuredly not neccesarily Dopplerian; anyone in space physics knows, there ain't no absolute/ Pascalian plenum -- not his fault, either, although Hubble succumbed to the einsteinmaniacs! > > And b4 he UNDERSTOOD what they physically OR mathematically require > > or impose or mean. thus: yeah, there is at least one pair of such "fixed" points, but I would apply Boyles law, minimally, to that situation. > It does not imply that the temperature at every point is the same as > at its antipode. Nor does it imply (contrary to Tom's claim) that > "identical weather conditions" occur at some point and its antipode -- > unless "identical weather conditions" simply means the same in some > one continuous function (temperature or wind speed or ...). --les OEuvres! http://wlym.com
From: Konstantin Smirnov on 12 Feb 2010 15:23
And does it have sense to minimize transportation cost if some data are subdetermined (in [a,b]), for ex., distances/fuel prices from vendors to buyers are not exactly known because of possible traffic jams etc.? Do you see sense in a matrix of interval supply numbers for each vendors? For ex. Buyer 1 -- Buyer 2 Vendor 1 5 (11,15) Vendor 2 0 20 Vendor 3 (100,110) 10 Something like this - we have minimized the total cost and found interval supply data. In this manner, is this task usually encountered? |