[graph-tool-tickets] [graph-tool] Ticket #156: OpenMP problem in katz and pagerank

graph-tool webmaster at skewed.de
Mon Jun 9 13:38:22 UTC 2014

#156: OpenMP problem in katz and pagerank
reopened enhancement
Reporter: anonymous
Owner: tiago peixoto
Priority: normal
Milestone: 2.2

Comment (by td):

(following my previous comment)

Behaviour is definitely hard to grasp.

I just tested on the 16CPU machine:

- Unshuffled: ~10s
- Shuffled: ~5.8s

I am currently running the shuffling multiple times to see if this affects the compute time significantly.

So far, what I have seen, on the 16CPU machine, running it multiple times:

- Unshuffled: stable at 9.8s
- Shuffle: Ranges from 5.8 to 6.8 seconds. Quite a significant difference (~14% difference).

In reply to your last reply:

It only includes the PR computation time. Code:

            t2 = time()
            n_iter = test(g)
            t3 = time()

With test():
def test(g):
    pr, n_iter = gt.centrality.pagerank(g, ret_iter=True, epsilon=epsilon, max_iter=max_iter)
    return n_iter

Although max_iter and epsilon are specified, they are equal to 1e-6 (default) and 100 (more than necessary).

Is there any binary of the git version? I wanted to try it but I got quite discourage by the amount of requirements (plus it looks like compilation would take a lot of time). I am currently using the Ubuntu binary.

What does the "dynamic" OpenMP scheduling does, compared to static scheduling? It increases and reduces the number of threads depending on how fast things go?

Ticket URL: <URL:http://graph-tool.skewed.de/ticket/156>
graph-tool <URL:http://graph-tool.skewed.de>
An efficient python module for graph analysis and manipulation.

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