PDDL - Planning the moving of a vehicle

Question

Here is a very domain file that moves a submarine from one location to another:

(define (domain unnamed1)
    (:requirements
        :strips :typing)

    (:types
        location; check if at command-centre, shallow water, deep water, land
        personnel; human occupation
        sub; vehicle
    )

    (:predicates
        (sub_at ?s - sub ?loc - location); check if sub is at a specific location

        (is_pilot ?p - personnel)

        (deep_water ?loc - location)
        (shallow_water ?loc - location)
        (land ?loc - location)

        (adjacent-to ?t1 - location ?t2 - location); 
    )

    (:action move
        :parameters
            (?s - sub ?from - location ?to - location ?p - personnel ?c - capacity)
        :precondition
            (and
                (sub_at ?s ?from); check where the subs starting location is
                (or ;check if 'starting location' is adjacent to destination
                    (adjacent-to ?to ?from)
                    (adjacent-to ?from ?to)
                );
                (or; Check if in water
                    (shallow_water ?to)
                    (deep_water ?to)
                )
                (is_pilot ?p); check if member is a pilot
            )
        :effect
            (and
                (sub_at ?s ?to); sub is now at destination
                (not (sub_at ?s ?from)); Sub is no longer at starting point
            )
    )

)

The above domain file follows three very simple requirements:

1. The location a submarine can move to must be adjacent to the location the submarine is already in. Ex: If the submarine is at location X and wants to move to Y, Y must be adjacent to X.

2. The location to be moved to must be in deep/shallow water and,

3. There must be a pilot onboard.

Here is a problem file that moves the submarine from the command-centre to the first location. This works.

(define (problem underwater_problem)
    (:domain unnamed1)

    (:objects
        command-centre - location
        loc1 - location
        loc2 - location
        persPilot - personnel
        subm - sub
    )

        
    (:init
        (sub_at subm command-centre)
        (adjacent-to command-centre loc1)
        (adjacent-to loc1 loc2)
    
        (shallow_water loc1)
        (deep_water loc2)
    
        (is_pilot persPilot)
    )


    (:goal
        (sub_at subm loc1)
    )
)

The problem is here. I want the sub to jump across many different locations:

(define (problem underwater_problem)
    (:domain unnamed1)

    (:objects
        command-centre - location
        loc1 - location
        loc2 - location
        persPilot - personnel
        subm - sub
    )

        
    (:init
        (sub_at subm command-centre)
        (adjacent-to command-centre loc1)
        (adjacent-to loc1 loc2)
    
        (shallow_water loc1)
        (deep_water loc2)
    
        (is_pilot persPilot)
    )


    (:goal
        (and
            (sub_at subm loc1)
            (sub_at subm loc2)
        )
    )
)

Unfortunately, the following error is returned:

Suspected timeout.

 --- OK.
 Match tree built with 3 nodes.

PDDL problem description loaded: 
    Domain: UNNAMED1
    Problem: UNDERWATER_PROBLEM
    #Actions: 3
    #Fluents: 3
Landmarks found: 2
Starting search with IW (time budget is 60 secs)...
rel_plan size: 2
#RP_fluents 2
Caption
{#goals, #UNnachieved,  #Achieved} -> IW(max_w)

{2/1/0}:IW(1) -> [2][3][4];; NOT I-REACHABLE ;;
Total time: 2.5e-05
Nodes generated during search: 4
Nodes expanded during search: 4
IW search completed
Starting search with BFS(novel,land,h_add)...
--[4294967295 / 3]--
--[3 / 3]--
--[3 / 1]--
--[2 / 1]--
--[1 / 1]--
Total time: 1.2e-05
Nodes generated during search: 4
Nodes expanded during search: 3
Plan found with cost: 2.8026e-45
BFS search completed

I have no clue what any of this means.

Answer 1

Your goal asks the planner to bring the submarine to two places at once:

    (:goal
        (and
            (sub_at subm loc1)
            (sub_at subm loc2)
        )
    )

If you remove (sub_at subm loc1) it should work.