From: FAROUK AMINU <f.aminu_at_lancaster.ac.uk>

Date: Mon 23 Oct 2000 06:04:00 PM GMT

Message-ID: <Pine.GSO.4.21.0010231749040.21164-100000@unixa.lancs.ac.uk>

Date: Mon 23 Oct 2000 06:04:00 PM GMT

Message-ID: <Pine.GSO.4.21.0010231749040.21164-100000@unixa.lancs.ac.uk>

Dear Warwick, I will start by forwarding my gratitute to you for having sometime to go through my problem. To answer your questions, actually what I would like to implement is a case where I have n-nodes of a graph with costs Ci, i = 1,..,n associated with the edges of the graph. Cij are costs of going from node i to node j. The ordering I need to implement is just like a sequence of the edges such that the costs for traversing edge i (Ci) is the accumulated cost of all the edges traversed so far plus the cost of going from the second node of the previous edge to the first node of the current edge plus the cost of traversing the current edge itself. I presented the problem this way because I need to know exactly which edge is traversed after which and what is the resulting cost? I also intend to have the Cis to be the accumulators so as to be able to impose some restrictions on each of the Cis. It took me some long time thinking on how to make the Cis take their values based on the positions of the edges in the sequence. The only thing that could come to my mind was using if-then-else, but this could mean writing the constraints n! times because any permutation of the edges needs a new constraint, in the situation where n is big then this is not possible. I presented a three node version of the problem but in essence I need to implement a bigger version of the problem with a large number of nodes. I shall try your formulation and thank you once more for your kind assistance. with regards, Farouk =============================================================================== UMARU FAROUK AMINU DEPARTMENT OF MANAGEMENT SCIENCE LANCASTER UNIVERSITY LANCASTER LA1 4YX U.K. +44 (0)1524 593865 (School) +44 (0)1524 383619 (Home) +44 (0)1524 844885 (Fax)Received on Mon Oct 23 19:04:11 2000

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