Talk:Edmonds–Karp algorithm

message: In the article, it is stated that "The distinguishing feature is that the shortest augmenting path is used at each step, which guarantees that the computation will terminate." However, as I understand it, the use of the shortest augmenting path ensure a faster running time than using breadth-running time. The terminiation of the computation is also ensured in the other algorithms based on Ford-Fulkerson, and has as such nothing to do with the breadth-first search.
I will try to work on this entry at a later stage.--Kristjan Wager 09:52, 31 May 2005 (UTC)
replies: text: The article is precisely correct!  Please don't change it without discussion.  --Zero 13:42, 31 May 2005 (UTC)
replies: text: According to Cormen et al's Introduction to Algorithms, 2nd edition, the breadth-first search is done to reduce the search time from O(E|f^*|) to O(VE^2) (see pages 658-663).   It has nothing as do with ensuring that the algorithm terminates - this is ensured by the principles of the Ford-Fulkerson method.--Kristjan Wager 14:09, 31 May 2005 (UTC)

text: No, the O(E|f^*|) bound only applies if the capacities are integers.  If they are arbitrary real numbers, the Ford-Fulkerson method might fail to terminate and can even converge towards the wrong answer. See Ford-Fulkerson algorithm.  --Zero 20:08, 31 May 2005 (UTC)
replies: text:  Ok, thank you for clearifying. While I was aware of the problems with Ford-Fulkerson in regards to real numbers, I was unaware that Edmonds-Karp fixed it. Interesting that Cormen et al didn't mention that aspect. I think I need to read the original article. --Kristjan Wager 07:34, 1 Jun 2005 (UTC)

text: The arrow is drawn correctly. What happens here is that flow is "sent back" from E to D. The flow that was going from D to E is redirected to go to F. Klem fra Nils Grimsmo 15:18, 20 November 2006 (UTC)

text: Oops. Thank you for notifying! Klem fra Nils Grimsmo 06:56, 24 January 2007 (UTC)

text: Note how values are updated when backtracking the path. The net flow is maintained. Skew symmetry is upheld. Klem fra Nils Grimsmo 20:29, 25 March 2007 (UTC)

text: No, the capacity is five. You should only count edges from the source set S to the sink set T. edge D,E is from T to S, and therefore does not increase the capacity. ArrowmanCoder (talk) 01:40, 20 February 2009 (UTC)
thread_title: Discussion

message: In the example can you explain why that's the minimum cut and how you find it?  —Preceding unsigned comment added by 151.68.39.88 (talk) 11:56, 8 February 2010 (UTC)
thread_title:  Minimum Cut 

message: Or am I missing something?
Damix 217.202.48.196 (talk) 23:42, 10 September 2011 (UTC)
thread_title:  Should BreadthFirstSearch take F as a parameter? 

message: Edmonds Karp is sometimes implemented using fatest path instead of shortest path. This has a runtime of O(|E|^2*logC) with C being the max flow. (for sparse graphs it's O(|E|logC*(|E|+|V|log|V|)) using Dijkstra).
I guess |V| rarely much larger than logC, but perhaps the variation should be mentioned for completeness?  — Preceding unsigned comment added by Thomasda (talk • contribs) 00:12, 28 February 2012 (UTC)
thread_title:  Fatest pipe heuristic 

message: Will this algorithm work correctly for edge weights of zero?  If so, will the result always, sometimes, or never include those edges in the min-cut?
Will the algorithm work correctly if edge weights are negative?
Thanks,128.112.139.195 (talk) 21:28, 16 July 2012 (UTC)
thread_title:  Edge weights must be: non-zero? positive? 

message: The pseudocode uses "push" and "pop" for the queue handling. Push is fine, but pop (LIFO) will result in an algorithm that is extremely slow compared to shifting (FIFO).  — Preceding unsigned comment added by 94.255.217.210 (talk) 21:16, 18 October 2012 (UTC)
thread_title: Push and pop

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message: It seems to me that the search can and should stop as soon as the sink node is reached. Indeed, all later processing is superfluous, as pred[t] can only be set once in each search.
As it is now, the search stops when the queue is empty. In the first pass, that happens only after all nodes reachable from the source have been visited.
JohannDeneux (talk) 15:45, 22 February 2020 (UTC)
thread_title:  Incorrect pseudo-code for the breadth-first-search part