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. -- 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
tabling.clj
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