On Wed, Sep 26, 2012 at 8:20 AM, Reinout Stevens <reste...@vub.ac.be> 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 -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
