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Re: [Help-glpk] modeling variable "chains"
From: |
Michael Hennebry |
Subject: |
Re: [Help-glpk] modeling variable "chains" |
Date: |
Fri, 14 Aug 2009 11:21:03 -0500 (CDT) |
User-agent: |
Alpine 1.00 (DEB 882 2007-12-20) |
On Thu, 13 Aug 2009, Yaron Kretchmer wrote:
Yes, I haven't thought of that- is that similar to eliminating subtours in
TSP?
I don't have enough details about what you are trying to do,
e.g., I don't understand R1->R2->R2->R1.
Why two R2s?
Possibly you will have a CTP (capacitated
transshipment problem) with side constraints.
The side constraints might be to ensure
that the paths connect the right things.
If arcs like R2->R2 are desired,
generating them might be difficult.
On Thu, Aug 13, 2009 at 3:00 PM, Michael Hennebry <
address@hidden> wrote:
On Thu, 13 Aug 2009, Yaron Kretchmer wrote:
I've modeled the resources, and created an array of binary variables which
describe whether a certain resource exists in a certain X/Y location.
I'm having difficulties modeling the "paths". My difficulty is this:
- Each path maps to a pattern of resources (for instance R1->R2->R2->R1).
I
can successfully describe the path contents (i.e. the fact that it
contains
2 R1's, and 2 R2's), but how can I describe the order i.e. how do I
capture
the fact the pattern has to contain adjacent resources (i.e. you don't
want
a path to include disjoint resources that are spread around your chip, you
want resources that are in adjanct X/Y coordinates.
So my question:
*) How do I model the constraint that the resources mapping to a path need
to have consecutive X or Y coordinates?
This is a lot like finding a path in a sparse graph.
Try having binary variables for the arcs instead of the nodes.
--
Michael address@hidden
"Pessimist: The glass is half empty.
Optimist: The glass is half full.
Engineer: The glass is twice as big as it needs to be."