walk* exponential in depth of tree terms?

Question

By 'reification' I mean e.g.:

(run 1 [t] (== t <some-constant-to-be-reified>))

Demonstration of exponential performance, using nested vectors ((link: ], [[]], [[[]])...):
https://www.refheap.com/1e30c198d528300fcba9ef24a

Is this expected, or a bug? I'm guessing the former, but hoping the latter. Feel free to close without comment if this is just the way it is. :)

Answer 1

Comment made by: tomoj

Attached patch 0001-Walk-less.patch gets me (link: https://www.refheap.com/39b990aed519346c2e41afcbe text: this nice result). It also makes my real case work quite speedily (25ms now, where before it took so long that I never saw it finish). That's a huge relief!

The problem wasn't reification, but walk-term. In the patch I attempt to avoid doing some walking which appears to be redundant. I hope the fact that most of the tests still pass is good evidence that it's redundant.

However, the patch breaks some unifier tests. I noticed that my refheap test 'passes' as of bd65104ec3~, but fails as of bd65104ec3 (the patch for LOGIC-69). It seems the fix made the unifier rely on the current behavior of walk-term.

I'm going to press on with my patched ./checkouts copy for now, since I'm not using the unifier. I may come back to try to fix it sometime.

Answer 2

Reference: https://clojure.atlassian.net/browse/LOGIC-166 (reported by tomoj)