Answer Set Programming Beginner

Question

I am a beginner in Answer Set Programming and completely new to clingo. I tried the facts and constraints below on nurses shift on clingo, but I am not getting any model and clingo not flagging any error. I keep getting UNSAT. What am I not doing right?

nurselimits(x, min, max). 
worklimits(min, max).
daylimits(x, t, min, max).
x(morning; afternoon; night; off; leave).
x(1..5).


day(1..28).
days(28).
nurse(1..40).
shift(1, morning, 8).
shift(2, afternoon, 14).
shift(3, night, 20).
shift(4, off, 0).
shift(5, leave, 10).
nurselimits(1,6,9).
nurselimits(2,6,9).
nurselimits(3,4,7).
daylimits(1,8,6,9).
daylimits(2,8,6,9).
daylimits(3,8,5,10).
worklimits(132,228).



 {assign(N, X, D) : shift(X, Name, H), X != 4, X != 5} = 1:- nurse(N), day(D).



:- day(D), #count{N : assign(N, X, D)} > max, nurselimits(x, min, max).
:- day(D), #count{N : assign(N, X, D)} < min, nurselimits(x, min, max).

:- nurse(N), #sum{H, D : assign(N, X, D), shift(X, Name, H)} > max, worklimits(min, max).
:- nurse(N), #sum{H, D : assign(N, X, D), shift(X, Name, H)} < min, worklimits(min, max).


:- nurse(N), assign(N, X1, D), assign(N, X2, D+1), X2 < X1 , X1 <= 3.

:- nurse(N), day(D), days(DAYS), D <= DAYS-21, 
   #count{D1 : assign(N, 4, D1), D1 >= D, D1 <= D+21} = 1.


:- nurse(N), #count{D: assign(N, X, D)} > max, daylimits(x, t, min, max).

:- nurse(N), #count{D: assign(N, X, D)} < min, daylimits(x, t, min, max).

Please edit your question title to something that actually describes a problem or asks a question. It should be clear and descriptive enough to be of use to a future user of this site who is scanning through a list of search results looking for a problem solution. Your current title provides nothing meaningful that will help that user. Thanks. — Ken White
– Ken White, Commented Mar 11, 2020 at 12:29

user1747134 · Accepted Answer · 2021-03-28 11:56:51Z

1

In this code

nurselimits(x, min, max). 
worklimits(min, max).
daylimits(x, t, min, max).
x(morning; afternoon; night; off; leave).
x(1..5).

There are several problems. The symbols x, min, max, t. Are all non-numerical symbolic constants, much like morning, afternoon,etc. That is probably unintended, unless you are substituting them using the -c command line option. Certainly, the x in nurselimits has nothing to do with the x(1..5) in your code, which also seems unintended. Also, the constant min is the same symbolic value in nurselimits, worklimits and daylimits. Perhaps you wanted it to be variable instead?

answered Mar 28, 2021 at 11:56

user1747134

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Comments

nicole.ts · Accepted Answer · 2020-06-16 13:11:45Z

0

You should remove first three lines and add #show (e.g. #show assign/3.) of any predicate you want to see in the answer sets.

answered Jun 16, 2020 at 13:11

nicole.ts

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