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Prolog代写 | COMP3411/9814 Assignment 1 – Prolog and Search

COMP3411/9814 Artificial Intelligence Term 1, 2021 DRAFT Assignment 1 – Prolog and Search

Part 1 – Prolog

In this part, you are to write some Prolog programs.

At the top of your 8ile, place a comment containing your full name, student number and assignment name. You may add additional information like the date the program was completed, etc. if you wish.

At the start of each Prolog predicate, write a comment describing the operation of the predicate.

Testing Your Code

A signi8icant part of completing this assignment will be testing the code you write to make sure that it works correctly. To do this, you will need to design test cases that exercise every part of the code.
You should pay particular attention to “boundary cases”, that is, what happens when the data you are testing with is very small, or in some way special. For

example:
• What happens when the list you input has no members, or only one member?
• Does you code work for lists with both even and odd numbers of members?
• Does your code work for negative numbers?

Note: not all of these matter in all cases, so for example with sqrt_table, negative numbers don’t have square roots, so it doesn’t make sense to ask whether your code works with negative numbers.

With each question, some example test data are provided to clarify what the code is intended to do. You need to design further test data. Testing, and designing test cases, is part of the total programming task.

It is important to use exactly the names given below for your predicates, otherwise the automated testing procedure will not be able to 9ind your predicates and you will lose marks. Even the capitalisation of your predicate names must be as given below.

Question 1.1: List Processing

Write a predicate sumsq_even(Numbers, Sum) that sums the squares of only the even numbers in a list of integers.
Example:
?- sumsq_even([1,3,5,2,-4,6,8,-7], Sum).
Sum = 120

Note that it is the element of the list, not its position, that should be tested for oddness. (The example computes 2*2 + (-4)*(-4) + 6*6 + 8*8). Think carefully about how the predicate should behave on the empty list — should it fail or is there a reasonable value that Sum can be bound to?

To decide whether a number is even or odd, you can use the built-in Prolog operator N mod M, which computes the remainder after dividing the whole number N by the whole number M. Thus a number N is even if the goal 0 is N mod 2 succeeds. Remember that arithmetic expressions like X + 1 and N mod M are only evaluated, in Prolog, if they appear after the is operator. So 0 is N mod 2 works, but N mod 2 is 0 doesn’t work.

Question 1.2: List Processing

Eliza was the name of the first “chatbot” written by Joseph Weizenbaum at MIT in the
mid-1960s. It pretended to be a psychiatrist, so that it only had to do simple transformations on the input and turn a statement into a sentence. If a sentence is represented by a list of words, an example of a simple transformation is:
?- eliza1([you,do,not,like,me], X).
X = [what,makes,you,say,i,do,not,like,you]

Here, the simple transformation is to put “What makes you say” in the front of the sentence and replace “you” with “i” and “me” with “you”.

Write a Prolog program that takes a sentence in the form of a list and replaces any occurrence:
you → i me → you my → your
and prepends the list [what, makes, you, say] to the transformed list.

Note 1: your predicate MUST be called “eliza1”. Don’t forget the “1”.

Note 2: To prevent trying to print lists that are accidentally too long, SWI Prolog limits the number of elements in a list that it prints. You might see the answer to your query ending with [a, b c | …]. You can force SWI Prolog to print longer lists with the directive
:- set_prolog_flag(answer_write_options,[max_depth(0)]).
which you can put at the top of your file. max_depth(0) means no limit.

Question 1.3: List Processing

The rules in Question 1.2 work if “you” starts a sentence but won’t make much sense for an example like this:
?- eliza1([i,wonder,if,you,would,help,me,learn,prolog], X).
X = [what,makes,you,say,i,if,wonder,i,would,help,you,learn,prolog]
What would be better is:
?- eliza2([i,wonder,if,you,would,help,me,learn,prolog], X).
X = [what,makes,you,think,i,would,help,you]
Write a predicate eliza2 (don’t forget the “2”) that takes a list of words: [ …, you, , me, …]
and creates a new list of the form:
[what, makes, you, think, i, , you]
i.e. skip the words before “you” and after “me”, and insert the words in between “you”
and “me” into the new sentence between “i” and “you”.

Hint: You can use the built-in predicate “append(X, Y, Z)” to do a lot of the work for you. Remember, “append” can be used to split a list, as well as concatenating lists.

Question 1.4: Prolog Terms

Arithmetic expressions can be written in prefix format, e.g 1+2*3 can be written as add(1,mul(2,3)). Iftheoperatorsavailableareadd,sub,mul,div,writea Prolog program, eval(Expr, Val), that will evaluate an expression, e.g.
?- eval(add(1, mul(2, 3)), V).
V=7
?- eval(div(add(1, mul(2, 3)), 2), V). V = 3.5

Testing

This assignment will be marked on functionality in the first instance. However, you should always adhere to good programming practices in regard to structure, style and comments, as described in the Prolog Dictionary. Submissions that score very low in the automarking will be examined by a human marker, and may be awarded a few marks, provided the code is readable.

Your code must work under the version of SWI Prolog used on the Linux machines in the UNSW School of Computer Science and Engineering. If you develop your code on any other platform, it is your responsibility to re-test and, if necessary, correct your code when you transfer it to a CSE Linux machine prior to submission.

Your code will be run on a few simple tests when you submit. So, it is a good idea to submit early and often so that potential problems with your code can be detected early. You will be notified at submission time if your code produces any compiler warnings. Please ensure that your final submission does not produce any such warnings (otherwise, marks will be deducted).

Part 2 – Search Question 1: Search Algorithms for the 15-Puzzle

In this question you will construct a table showing the number of states expanded when the 15-puzzle is solved, from various starting positions, using four different searches:

(i) Uniform Cost Search (with Dijkstra’s Algorithm) (ii) Iterative Deepening Search
(iii) A*Search (using the Manhattan Distance heuristic)
(iv) Iterative Deepening A* Search

Go to theWebCMS. Under “Assignments” you will find Prolog Search Code
“prolog_search.zip”. Unzip the file and change directory to prolog search, e.g. unzip prolog_search.zip
cd prolog_search
Start prolog and load puzzle15.pl and ucsdijkstra.pl by typing

[puzzle15]. [ucsdijkstra].

Then invoke the search for the specified start10 position by typing
start10(Pos),solve(Pos,Sol,G,N),showsol(Sol).
When the answer comes back, just hit Enter/Return. This version of Uniform Cost Search (UCS) uses Dijkstra’s algorithm which is memory efficient, but is designed to return only one answer. Note that the length of the path is returned as G, and the total number of states expanded during the search is returned as N.

a) Draw up a table with four rows and five columns. Label the rows as UCS, IDS, A* and IDA*, and the columns as start10, start12, start20, start30
and start40. Run each of the following algorithms on each of the 5 start states:

(i)[ucsdijkstra] (ii)[ideepsearch] (iii)[astar] (iv)[idastar]
In each case, record in your table the number of nodes generated during the search. If the algorithm runs out of memory, just write “Mem” in your table. If the code runs for five minutes without producing out- put, terminate the process by typing Control-C and then “a”, and write “Time” in your table. Note that you will need to

b)Briefly discuss the efficiency of these four algorithms (including both time and
In each case, record in your table the number of nodes generated dur-
ing the search. If the algorithm runs out of memory, just write “Mem”
in your table. If the code runs for five minutes without producing out-
put, terminate the process by typing Control-C and then “a”, and write
“Time” in your table. Note that you will need to re-start prolog each
re-start prolog each time you switch to a different search.
time you switch to a different search.

(b) Briefly discuss the efficiency of these four algorithms (including both time
memory usage).
and memory usage).

Question 2: Heuristic Path Search for 15-Puzzle

In this question you will be exploring an Iterative Deepening version of the

In this question you will be exploring an Iterative Deepening version of the Heuristic

Heuristic Path Search algorithm discussed in the Week 4 Tutorial. Draw up
Path Search algorithm discussed in the Week 3 Tutorial. Draw up a table in the
a table in the following format:
following format:
start50
start60
start64
IDA∗
50
14642512
60
321252368
64
1209086782
1.2 1.4 1.6
Greedy

The top row of the table has been filled in for you (to save you from running some
The top row of the table has been filled in for you (to save you from running
rather long computations).
some rather long computations).

(a) Run [greedy] forstart50, start60 and start64, and record the values returned for G (a) Run [greedy] for start50, start60 and start64, and record the values
and N in the last row of your table (using the Manhattan Distance heuristic defined
returned for G and N in the last row of your table (using the Manhattan in puzzle15.pl).
Distance heuristic defined in puzzle15.pl).

(b) Now copy idastar.pl to a new file heuristic.pl and modify the code of this new file so

(b) Now copy idastar.pl to a new file heuristic.pl and modify the code of that it uses an Iterative Deepening version of the Heuristic Path Search algorithm
this new file so that it uses an Iterative Deepening version of the Heuristic
discussed in the Weak 2 Tutorial Exercise, with w = 1.2 .

Path Search algorithm discussed in the Week 4 Tutorial Exercise, with
In your submitted document, briefly show the section of code that was changed, and
w = 1.2 .
the replacement code.

In your submitted document, briefly show the section of code that was (c) Runch[haenugreisdt,ica]nodn tshtaertr5e0p,lastcaermt6e0natncdosdtea.rt64 and record the values of G and N in
your table. Now modify your code so that the value of w is 1.4, 1.6 ; in each case,

(c) Run [heuristic] on start50, start60 and start64 and record the run the algorithm on the same three start states and record the values of G and N in
values of G and N in your table. Now modify your code so that the value your table.
of w is 1.4, 1.6 ; in each case, run the algorithm on the same three start states and record the values of G and N in your table.

(d) Briefly discuss the tradeoff between speed and quality of solution for these five algorithms.

(d) Briefly discuss the tradeoff between speed and quality of solution for these five algorithms.
Submitting your assignment

Your submission will consist of two files: assign1_part1.pl should contain all of your Prolog programs; and assign1_part2.pdf2should contain the results of your search experiments in part 2.
To hand in, log in to a School of CSE Linux workstation or server, make sure that your files are in the current working directory, and use the Unix command:
% give cs3411 assign1 assign1_part1.pl assign1_part2.pdf


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