Rank: 2594 based on 44 downloads (last 30 days) and 2 files submitted
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Derek O'Connor

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Company/University
University College Dublin, Retired
Lat/Long
53.021988, -6.611272

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Professional Interests:
Algorithms and Data Structures, Numerical Analysis

 

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18 Sep 2012 Screenshot The Bellman-Ford-Moore Shortest Path Algorithm A simple, efficient sparse implementation of the original Bellman-Ford-Moore Shortest Path Algorithm Author: Derek O'Connor shortest paths, sparse graphs 35 9
  • 5.0
5.0 | 1 rating
26 Jan 2011 Screenshot RPG Lab A set of functions for generating and testing random permutations of the integers (1,2, ..., n). Author: Derek O'Connor random permutation ge..., derangements, cyclic permutations 9 9
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5.0 | 2 ratings
Comments and Ratings by Derek View all
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08 Mar 2013 The Bellman-Ford-Moore Shortest Path Algorithm A simple, efficient sparse implementation of the original Bellman-Ford-Moore Shortest Path Algorithm Author: Derek O'Connor

@none Thanks for your compliments.

I would be grateful if you would post or send me your results for these REAL problems.

For example, I have not been able to find the official optimum solutions to the problems. This makes me uneasy.

07 Mar 2013 The Bellman-Ford-Moore Shortest Path Algorithm A simple, efficient sparse implementation of the original Bellman-Ford-Moore Shortest Path Algorithm Author: Derek O'Connor

This file is not there because I did not have room for the larger files on my website. I pointed this out at the start of TestBFNOTMaps.m

All the USA files are available here:

http://www.dis.uniroma1.it/challenge9/download.shtml

02 Nov 2012 The Bellman-Ford-Moore Shortest Path Algorithm A simple, efficient sparse implementation of the original Bellman-Ford-Moore Shortest Path Algorithm Author: Derek O'Connor

I have corrected an error in BFMSpathOT.m The two variables 'head' and 'tail' were switched which resulted in the directed arcs of the network being reversed.

OLD: [m,n,p,D,tail,head,W] = Initialize(spG);

NEW: [m,n,p,D,head,tail,W] = Initialize(spG);

This means that the old version gave the wrong answers [p D]. However, this change does not affect the analysis and running time of the algorithm.

02 Nov 2012 The Bellman-Ford-Moore Shortest Path Algorithm A simple, efficient sparse implementation of the original Bellman-Ford-Moore Shortest Path Algorithm Author: Derek O'Connor

The updated Matlab function BFMSpathOT.m can be found at:

http://www.scribd.com/doc/105903247/O-Connor-The-Bellman-Ford-Moore-Shortest-Path-Algorithm.m

19 Oct 2012 The Bellman-Ford-Moore Shortest Path Algorithm A simple, efficient sparse implementation of the original Bellman-Ford-Moore Shortest Path Algorithm Author: Derek O'Connor

I have an important update to this submission which corrects an error but the UPDATE process fails each time I use it.

Derek O'Connor

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08 May 2013 The Bellman-Ford-Moore Shortest Path Algorithm A simple, efficient sparse implementation of the original Bellman-Ford-Moore Shortest Path Algorithm Author: Derek O'Connor Roland

Dear Derek,
Do I understand correctly when I say that your function is only capable of computing the shortest path between a root and all other nodes. I am looking for a function that efficiently computes shortest paths between all nodes in a subset of the nodes of the whole graph.
Do I understand your code correctly when I say the following:
- I would have to call the function multiple times (for each root). It is not possible to specify r as a vector of roots? In other words, this algorithm does not save any info when you have to compute path from multiple roots.
- All computation spent on shortest paths to nodes that I do not need is lost. Is this really necessary (i.e. inherent to the Bellman-Ford algorithm) or could this could become faster if it is adapted to the situation I need it for?
Thank you very much for your reply.
Kind regards.
Roland

11 Mar 2013 The Bellman-Ford-Moore Shortest Path Algorithm A simple, efficient sparse implementation of the original Bellman-Ford-Moore Shortest Path Algorithm Author: Derek O'Connor none

Derek, I sent you an email outlining the real problem data/context etc.

I look forward to your reply!

08 Mar 2013 The Bellman-Ford-Moore Shortest Path Algorithm A simple, efficient sparse implementation of the original Bellman-Ford-Moore Shortest Path Algorithm Author: Derek O'Connor O'Connor, Derek

@none Thanks for your compliments.

I would be grateful if you would post or send me your results for these REAL problems.

For example, I have not been able to find the official optimum solutions to the problems. This makes me uneasy.

08 Mar 2013 The Bellman-Ford-Moore Shortest Path Algorithm A simple, efficient sparse implementation of the original Bellman-Ford-Moore Shortest Path Algorithm Author: Derek O'Connor none

My mistake! Yes I can see you have written it in.

Excellent algo that works straight out of the box.

07 Mar 2013 The Bellman-Ford-Moore Shortest Path Algorithm A simple, efficient sparse implementation of the original Bellman-Ford-Moore Shortest Path Algorithm Author: Derek O'Connor O'Connor, Derek

This file is not there because I did not have room for the larger files on my website. I pointed this out at the start of TestBFNOTMaps.m

All the USA files are available here:

http://www.dis.uniroma1.it/challenge9/download.shtml

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