Op woensdag 26 september 2012 22:21:26 UTC+2 schreef David Nolen het volgende: > > On Wed, Sep 26, 2012 at 8:20 AM, Reinout Stevens > <rest...@vub.ac.be<javascript:> > > wrote: > >> Hi, >> >> >> I'm the author of a DSL that allows reasoning over paths throughout >> graphs using core.logic ( https://github.com/ReinoutStevens/damp.qwal ). >> We noticed that for larger graphs performance became horribly slow, even >> though there is no apparent reason why it should be. First investigations >> lead me to believe tabling was the issue. We use tabling to prevent >> infinite loops due to cycles in the graph. After writing a small testcase >> that exhibits the described problems I've noticed that it is a combination >> of tabling and looping over a list. >> >> In the test case we construct a linear graph (so: a graph where each node >> has a single successor). We want to asser that there exists a path from the >> start to the end node. This is done by using the logical rule trans >> [graph current next], which given a graph and the current node binds next to >> the possible successors. We write this query in three different ways. >> First, we try to succeed the goal trans as many times as needed, until we >> end up in the end state. Next, we do the same but tabling our loop. This >> prevents looping in case our graph would contain a cycle (in this case, >> there is no such cycle). Finally, instead of directly proving trans, we >> prove a list of goals. This list contains a single goal (trans). This last >> scenario runs much slower than the previous two, even though I don't see a >> large difference with the first two scenarios. >> >> In attachment the code of our test case. There are 3 functions at the >> end, each implementing one of the described scenarios. Note the difference >> between solve-goal and solve-goals. >> >> Any pointers how to solve the issue, or work around it are appreciated >> > > Thanks for the feedback, I've created a ticket > http://dev.clojure.org/jira/browse/LOGIC-57 > > I will look into it. What version of core.logic are you using? Out of > curiosity did you experiment with a profiler at all and perhaps collected > some clues? > > David > > That would be version '0.7.5' I have used JVisualVM to look into it, but didn't find anything useful.
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