Issues with some axioms

[Sylindril]

The following domain/problem pairs seem to be valid under fast downward, but fail with kstar.

(define (domain gridworld-8x8)
(:requirements :strips :typing :negative-preconditions :equality :derived-predicates)
(:types cell)
(:constants c1-1 c2-1 c3-1 c4-1 c5-1 c6-1 c7-1 c8-1 c1-2 c2-2 c3-2 c4-2 c5-2 c6-2 c7-2 c8-2 c1-3 c2-3 c3-3 c4-3 c5-3 c6-3 c7-3 c8-3 c1-4 c2-4 c3-4 c4-4 c5-4 c6-4 c7-4 c8-4 c1-5 c2-5 c3-5 c4-5 c5-5 c6-5 c7-5 c8-5 c1-6 c2-6 c3-6 c4-6 c5-6 c6-6 c7-6 c8-6 c1-7 c2-7 c3-7 c4-7 c5-7 c6-7 c7-7 c8-7 c1-8 c2-8 c3-8 c4-8 c5-8 c6-8 c7-8 c8-8 - cell)
(:predicates (at ?c - cell) (wall ?c - cell) (north ?a ?b - cell) (south ?a ?b - cell) (east ?a ?b - cell) (west ?a ?b - cell))
(:derived (wall ?c) (or (= ?c c1-3) (= ?c c2-3) (= ?c c3-3) (= ?c c4-3) (= ?c c5-3) (= ?c c6-3)))
(:derived (north ?a ?b) (or (and (= ?a c1-1) (= ?b c1-2)) (and (= ?a c1-2) (= ?b c1-3)) (and (= ?a c1-3) (= ?b c1-4)) (and (= ?a c1-4) (= ?b c1-5)) (and (= ?a c1-5) (= ?b c1-6)) (and (= ?a c1-6) (= ?b c1-7)) (and (= ?a c1-7) (= ?b c1-8)) (and (= ?a c2-1) (= ?b c2-2)) (and (= ?a c2-2) (= ?b c2-3)) (and (= ?a c2-3) (= ?b c2-4)) (and (= ?a c2-4) (= ?b c2-5)) (and (= ?a c2-5) (= ?b c2-6)) (and (= ?a c2-6) (= ?b c2-7)) (and (= ?a c2-7) (= ?b c2-8)) (and (= ?a c3-1) (= ?b c3-2)) (and (= ?a c3-2) (= ?b c3-3)) (and (= ?a c3-3) (= ?b c3-4)) (and (= ?a c3-4) (= ?b c3-5)) (and (= ?a c3-5) (= ?b c3-6)) (and (= ?a c3-6) (= ?b c3-7)) (and (= ?a c3-7) (= ?b c3-8)) (and (= ?a c4-1) (= ?b c4-2)) (and (= ?a c4-2) (= ?b c4-3)) (and (= ?a c4-3) (= ?b c4-4)) (and (= ?a c4-4) (= ?b c4-5)) (and (= ?a c4-5) (= ?b c4-6)) (and (= ?a c4-6) (= ?b c4-7)) (and (= ?a c4-7) (= ?b c4-8)) (and (= ?a c5-1) (= ?b c5-2)) (and (= ?a c5-2) (= ?b c5-3)) (and (= ?a c5-3) (= ?b c5-4)) (and (= ?a c5-4) (= ?b c5-5)) (and (= ?a c5-5) (= ?b c5-6)) (and (= ?a c5-6) (= ?b c5-7)) (and (= ?a c5-7) (= ?b c5-8)) (and (= ?a c6-1) (= ?b c6-2)) (and (= ?a c6-2) (= ?b c6-3)) (and (= ?a c6-3) (= ?b c6-4)) (and (= ?a c6-4) (= ?b c6-5)) (and (= ?a c6-5) (= ?b c6-6)) (and (= ?a c6-6) (= ?b c6-7)) (and (= ?a c6-7) (= ?b c6-8)) (and (= ?a c7-1) (= ?b c7-2)) (and (= ?a c7-2) (= ?b c7-3)) (and (= ?a c7-3) (= ?b c7-4)) (and (= ?a c7-4) (= ?b c7-5)) (and (= ?a c7-5) (= ?b c7-6)) (and (= ?a c7-6) (= ?b c7-7)) (and (= ?a c7-7) (= ?b c7-8)) (and (= ?a c8-1) (= ?b c8-2)) (and (= ?a c8-2) (= ?b c8-3)) (and (= ?a c8-3) (= ?b c8-4)) (and (= ?a c8-4) (= ?b c8-5)) (and (= ?a c8-5) (= ?b c8-6)) (and (= ?a c8-6) (= ?b c8-7)) (and (= ?a c8-7) (= ?b c8-8))))
(:derived (south ?a ?b) (north ?b ?a))
(:derived (east ?a ?b) (or (and (= ?a c1-1) (= ?b c2-1)) (and (= ?a c1-2) (= ?b c2-2)) (and (= ?a c1-3) (= ?b c2-3)) (and (= ?a c1-4) (= ?b c2-4)) (and (= ?a c1-5) (= ?b c2-5)) (and (= ?a c1-6) (= ?b c2-6)) (and (= ?a c1-7) (= ?b c2-7)) (and (= ?a c1-8) (= ?b c2-8)) (and (= ?a c2-1) (= ?b c3-1)) (and (= ?a c2-2) (= ?b c3-2)) (and (= ?a c2-3) (= ?b c3-3)) (and (= ?a c2-4) (= ?b c3-4)) (and (= ?a c2-5) (= ?b c3-5)) (and (= ?a c2-6) (= ?b c3-6)) (and (= ?a c2-7) (= ?b c3-7)) (and (= ?a c2-8) (= ?b c3-8)) (and (= ?a c3-1) (= ?b c4-1)) (and (= ?a c3-2) (= ?b c4-2)) (and (= ?a c3-3) (= ?b c4-3)) (and (= ?a c3-4) (= ?b c4-4)) (and (= ?a c3-5) (= ?b c4-5)) (and (= ?a c3-6) (= ?b c4-6)) (and (= ?a c3-7) (= ?b c4-7)) (and (= ?a c3-8) (= ?b c4-8)) (and (= ?a c4-1) (= ?b c5-1)) (and (= ?a c4-2) (= ?b c5-2)) (and (= ?a c4-3) (= ?b c5-3)) (and (= ?a c4-4) (= ?b c5-4)) (and (= ?a c4-5) (= ?b c5-5)) (and (= ?a c4-6) (= ?b c5-6)) (and (= ?a c4-7) (= ?b c5-7)) (and (= ?a c4-8) (= ?b c5-8)) (and (= ?a c5-1) (= ?b c6-1)) (and (= ?a c5-2) (= ?b c6-2)) (and (= ?a c5-3) (= ?b c6-3)) (and (= ?a c5-4) (= ?b c6-4)) (and (= ?a c5-5) (= ?b c6-5)) (and (= ?a c5-6) (= ?b c6-6)) (and (= ?a c5-7) (= ?b c6-7)) (and (= ?a c5-8) (= ?b c6-8)) (and (= ?a c6-1) (= ?b c7-1)) (and (= ?a c6-2) (= ?b c7-2)) (and (= ?a c6-3) (= ?b c7-3)) (and (= ?a c6-4) (= ?b c7-4)) (and (= ?a c6-5) (= ?b c7-5)) (and (= ?a c6-6) (= ?b c7-6)) (and (= ?a c6-7) (= ?b c7-7)) (and (= ?a c6-8) (= ?b c7-8)) (and (= ?a c7-1) (= ?b c8-1)) (and (= ?a c7-2) (= ?b c8-2)) (and (= ?a c7-3) (= ?b c8-3)) (and (= ?a c7-4) (= ?b c8-4)) (and (= ?a c7-5) (= ?b c8-5)) (and (= ?a c7-6) (= ?b c8-6)) (and (= ?a c7-7) (= ?b c8-7)) (and (= ?a c7-8) (= ?b c8-8))))
(:derived (west ?a ?b) (east ?b ?a))
(:action move-north :parameters (?f ?t - cell) :precondition (and (at ?f) (north ?f ?t) (not (wall ?t))) :effect (and (not (at ?f)) (at ?t)))
(:action move-south :parameters (?f ?t - cell) :precondition (and (at ?f) (south ?f ?t) (not (wall ?t))) :effect (and (not (at ?f)) (at ?t)))
(:action move-east :parameters (?f ?t - cell) :precondition (and (at ?f) (east ?f ?t) (not (wall ?t))) :effect (and (not (at ?f)) (at ?t)))
(:action move-west :parameters (?f ?t - cell) :precondition (and (at ?f) (west ?f ?t) (not (wall ?t))) :effect (and (not (at ?f)) (at ?t)))
)

The above domain defines an 8x8 gridworld with a barrier in the middle, and the problem.pddl (below) only defines the start and goal locations.

(define (problem gw-task-158)
(:domain gridworld-8x8)
(:init (at c2-1))
(:goal (at c4-8))
)

[Sylindril]

Succesfully evaluates with astar(blind()) in fast downward, fails with similar heuristic in kstar

[Sino-Huang]

it seems that kstar does not support derived predicates?

[ctpelok77]

In principle, there is nothing that prevents K* to support derived predicates (assuming that the heuristic supports it), but it was not developed with the axioms in mind. So, it was not extensively tested on problems with derived predicates, and evidently there is a bug somewhere.

It is hard for me to find time to get to it, but people are welcome to take on the task - I can guess that the issue might be in the single goal state transformation.