FD logic doesn't always return all solutions

Description

Given the following code

(run* [x11 x12 x13 
       x21 x22     x24
       x31     x33 x34
           x42 x43 x44]
      (fd/in x11 x12 x13 x21 x22 x24 x31 x33 x34 x42 x43 x44 (fd/interval 1 9))
      (fd/eq (= (+ x11 (/ x12 x13))   5)
             (= (+ x21 (/ x22   2)) x24)
             (= (+ x31 (/   6 x33)) x34)
             (= (+   4 (/ x42 x43)) x44)
             (= (+ x11 (/ x21 x31))   4)
             (= (* x12 (/ x22   6)) x42)
             (= (+ x13 (-   2 x33)) x43)
             (= (+ (-  5 x24) x34)  x44)))

I have ([1 4 1 3 6 6 1 1 7 4 2 6] [2 6 2 4 6 7 2 1 8 6 3 6]) as a result.

However, as soon as I change (fd/interval 1 9) to (fd/interval 0 9), the result becomes an empty sequence. However, I expect it to include at least the two aforementioned solutions.

Environment

org.clojure/core.logic 0.8.8

Activity

David Nolen

March 10, 2015 at 8:49 PM

See also https://clojure.atlassian.net/browse/LOGIC-156#icft=LOGIC-156

David Nolen

November 10, 2014 at 12:09 AM

Thanks for the minimal case, yeah looks like an issue with fd/eq as it works fine if you write it out long hand.

import

October 21, 2014 at 2:08 PM

Comment made by: dnnx

I actually suspect that the bug is in `fd/eq`. Here is a smaller test case:

(run* [q]
      (fd/in q (fd/interval 1 2))
      (fd/eq (= (/ q q) 1)))

It returns `(1 2)` as expected, but as soon as I change `fd/interval` to `0 2`, it returns an empty seq.

David Nolen

October 21, 2014 at 10:34 AM

It would help if you could confirm that the issue is present without using fd/eq - which is just macro sugar. Writing out the long form is tedious but it will help isolate the issue. Thanks.

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Details

Assignee

David Nolen

Reporter

import

Labels

finite-domains

Priority

Major

Created October 20, 2014 at 7:18 PM

Updated March 10, 2015 at 8:49 PM