COMP1100 Assignment 3 Solution

In this assignment, you will develop a software agent or AI bot that plays "Consecutive Dots". Consecutive dots is similar to a game of Connect Four, however connections that wrap around the board are allowed.
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Overview of Tasks
This assignment is marked out of 100 for COMP1100 students.
| Task | Marks | |--------------------------|--------------| | Main Task: Consecutive Dots AI | 55 Marks | | Unit Tests | 10 Marks | | Coding
Style | 10 Marks | | Technical Report | 25 Marks |
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Getting Started
Fork the assignment repository and clone it to your computer, following the same steps as in Lab 2. The assignment repository is at https://gitlab.cecs.anu.edu.au/comp1100/2022s2/2022s2StudentFiles/assignment3.
Overview of the Game
The game starts with an empty $$8 imes 7$$ board with the following starting configuration: Initial State.
The blue token is considered player 1 and always moves first. The red token is considered player 2 and always moves second.
Players take turns choosing a column to "drop" their token into. Once dropped, the token falls until it reaches the bottom of the board, or an existing token of either colour. This token then takes up the slot in the next available row.
Otherwise if the player’s dropped token results in a run of 4 connected tokens in any direction (up, down, top-left to bottom-right diagonal, or bottom-left to top-right diagonal), even if the direction wraps around the board edge, then that player wins the game. The other player loses the game.
Overview of the Repository
Most of your code will be written in src/AI.hs, but you will also need to write tests in src/AITests.hs.
Other Files
src/ConsecutiveDots.hs implements the rules for Consecutive Dots. You should read through this file and familiarise yourself with the data declarations and the type signatures of the functions in it, as you will use some of these to analyse the game states. You do not need to understand how the functions in this file works in detail.
src/ConsecutiveDotsTests.hs implements some unit tests for the game. You are welcome to read through it.
src/AITests.hs is an empty file for you to write tests for your agent.
src/Testing.hs is a simple test framework similar to the one in Assignment 2. However, it has been extended so that you can group related tests together for clarity.
src/Dragons contains all the other code that makes the framework go. You do not need to read or understand anything in this directory. Here be dragons! (On medieval maps they drew pictures of dragons or sea monsters over uncharted areas.) The code in those files is beyond the areas of Haskell which this course explores.
Setup.hs tells cabal that this is a normal package with no unusual build steps. Some complex packages (that we will not see in this course) need to put more complex code here. You are not required to understand it. comp1100-assignment3.cabal tells the cabal build tool how to build your assignment. We will discuss how to use cabal below.
.ghcid tells the ghcid tool which command to run, which is what supplies VSCodium with error highlighting that automatically updates when you save a file.
.gitignore tells git which files it should not put into version control. These are often generated files, so it doesn't make sense to place them under version control.
Overview of Cabal
As before, we are using the cabal tool to build the assignment code. The commands provided are very similar to last time:
cabal v2-build: Compile your assignment.
cabal v2-run game: Build your assignment (if necessary), and run the test program. We discuss the test program in detail below, as there are a number of ways to launch it. cabal repl comp1100-assignment3: Run the GHCi interpreter over your project so you can test functions interactively.
cabal v2-test: Build and run the tests. This assignment is set up to run a unit test suite, and as with Assignment 2 you will be writing tests. The unit tests will abort on the first failure, or the first call to a function that is undefined.
cabal v2-haddock: Generate documentation in HTML format, which you can read with a web browser. This might be a nice way to read a summary of the game module, but it also documents the Dragons modules which you can safely ignore.
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You should execute these cabal commands in the top-level directory of your project: comp1100-assignment3 (i.e., the directory you are in when you launch a terminal from VSCodium).
Overview of the Test Program
To run the test program, you need to provide it with command line arguments that tell it who is playing. This command will let you play against the current "default" AI bot. Before you replace this with your own bot, the default will be firstLegalMove playing with COMP1100 rules: cabal v2-run game -- --p1 human --p2 ai
using ai to get the default AI is part of how we mark your assignment, so it is vital that you update your default bot to be whatever you want to be marked!
To play with a differently named AI, say, "greedy", use:
cabal v2-run game -- --p1 human --p2 ai:greedy
In general, the command to run the game looks like this:
cabal v2-run game -- ARGS
Replace ARGS with a collection of arguments from the following list:
--debug-lookahead: When an AI is done thinking, print out how many moves ahead it considered, and the candidate move it came up with at each level of lookahead. The first item in the printed list is the move it came up with at lookahead 1, the second item is the move it came up with at lookahead 2, and so on.
--ui codeworld: Show the game using CodeWorld. This is the default user interface. Use your web browser to play the game, as in previous assignments. Unlike the codeworld programs in previous assignments, you must terminate the program with Ctrl-C and restart it if you want to restart your game.
--ui text: Show the game in the terminal.
--ui json: Run a non-interactive game (i.e., AI vs AI, or AI vs network), and output a report of the game in JSON format. You probably won't have a use for this, but it's documented here for completeness.
--host PORT: Listen for a network connection on PORT. You only need this for network play (see below).
--connect HOST:PORT: Connect to someone else's game. You only need this for network play (see below).
--p1 PLAYER: Specify the white player. Required.
--p2 PLAYER: Specify the black player. Required.
The PLAYER parameters describe who is playing, and can take one of the following forms:
| Format | Effect | |-------------|-------------------------------------------------------------| | human | Ask the person at the computer for moves. | | ai | Ask the "default" AI for moves. | | ai:AINAME | Ask a specific AI for moves (example: ai:firstLegalMove). | | network |
Wait for a move from the network. |
Network Play
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Network play is provided in the hope that it will be useful, but we are unable to provide support for this feature, or diagnose problems related to tunnelling network connections between computers.
The assignment framework supports network play, so that you can test agents against each other without sharing code. One machine must host the game, and the other machine must connect to the game. In the example below, machine A hosts a game on port 5000 with the agent crashOverride as player 1, then machine B connects to the game, providing the AI chinook as player 2: ```
On Machine A:
cabal v2-run game -- --host 5000 --p1 ai:crashOverride --p2 network
On Machine B (you'll need Machine A's external IP address somehow):
cabal v2-run game -- --connect 198.51.100.66:5000 --p1 network --p2 ai:chinook ```
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Main Task: Consecutive Dots AI (COMP1100: 55 Marks)
Implement an AI (of type AIFunc, defined in src/AI.hs). There is a list called ais in that file, and we will mark the AI you call "default" in that list. This list is also where the framework looks when it tries to load an AI by name.
We will test your AI's performance by comparing it to implementations written by course staff, using a variety of standard approaches. Its performance against these AIs will form a large part of the marks for this Task.
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It is vital that you indicate one AI as "default", otherwise we will not know which one to mark. To indicate an AI as "default", you must have a (String, AIFunc) pair in the ais list of AIs in src/AI.hs where the String is precisely "default".
Understanding the AIFunc Type
The AIFunc type has two constructors, depending on whether you are implementing a simple AI that looks only at the current state, or a more complicated AI that performs look-ahead.
The NoLookahead constructor takes as its argument a function of type GameState -> Move. That is, the function you provide should look at the current state of the game and return the move to play. This constructor is intended for very simple AIs that do not look ahead in the game tree. As such, this function should never run for more than a moment at a time, but nevertheless, it is also subject to the timeout of 4 seconds.
Getting Started
This is a very open-ended task, and it will probably help if you build up your solution a little at a time. We suggest some approaches below.
A Move in Consecutive Dots corresponds to the index of the column in which you intend to drop a piece. If you try to apply a move that corresponds to a column that is already full, applyMove will return Nothing.
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First Legal Move
The simplest AI you can build is one that makes the first legal move it can. We have provided this for you, so you can see what a simple AI looks like.
Interlude: Heuristics
Heuristic functions are discussed in the lecture on game trees. We expect the quality of your heuristic function---how accurately it scores game states---to have a large impact on how well your AI performs. There is no obvious heuristic for this game, so you will need to get creative, or research heuristics that have been used in similar games. If you take the latter approach, be sure to cite all the sources that you access.
Greedy Strategy
“Greedy strategies†are the class of strategies that make moves that provide the greatest immediate advantage. In the context of this game, it means always making the move that will give it the greatest increase in heuristic. Try writing a heuristic and a greedy strategy, and see whether it beats our "first legal move" AI.
Interlude: Game Trees
Minimax
Greedy strategies can often miss opportunities that need some planning, and get tricked into silly traps by smarter opponents. The Minimax Algorithm was discussed in the lecture on game trees and will likely give better performance than a greedy strategy.
Pruning
Other Hints
There are four main ways your AI can be made smarter:
Heuristic: You will not have time to look all the way to the end of every possible game. Your heuristic function guesses how good a Game is for each player. If your heuristic is accurate, it will correctly identify strong and weak states.
Search Strategy: This determines how your AI decides which heuristic state to aim for. Greedy strategies look for the best state they can (according to the heuristic) and move towards that state. More sophisticated strategies like Minimax consider the opponent's moves when planning.
Pruning: if you can discard parts of the game tree without considering them in detail, you can process game trees faster and achieve a deeper look-ahead in the allotted running time. Alpha-beta pruning is one example; there are others.
Choosing a good heuristic function is very important, as it gives your AI a way to value its position that is smarter than just looking to see if the game is won or lost. Perhaps you might find that some squares are more valuable than others, when it comes to winning games, and so your AI should value them more highly.
Do not try to do everything at once. This does not work in production code and often does not work in assignment code either. Get something working, then take your improved understanding of the problem to the more complex algorithms.
As you refine your bots, test them against each other to see whether your changes are actually an improvement.
Unit Tests (10 Marks)
As with Assignment 2, you will be expected to write unit tests to convince yourself that your code is correct. The testing code has been extended from last time---src/Testing.hs now allows you to group tests into a tree structure. As before, you run the tests using cabal v2-test.
Your Task
Add tests to src/AITests.hs to test your AI.
Hints
Most of the hints from Assignment 2 apply here. Re-read those.
If a function is giving you an unexpected result, try breaking it into parts and writing tests for each part. This helps you isolate the incorrect parts, and gives you smaller functions to fix.
If your function has subtle details that need to be correct, think about writing tests to ensure those details do not get missed as you work on your code.
Coding Style (10 Marks)
As you write increasingly complex code, it is increasingly important that the code remains readable. This saves wasted effort understanding messy code, which makes it easier to think about the problem and your solution to it.
You MUST NOT edit any of the files in the framework (with the obvious exceptions of AI.hs and AITests.hs ).
Your Task
Ensure that your code is written in good Haskell style.
Technical Report (COMP1100: 25 Marks)
You are to write a concise technical report about your assignment.
The maximum word count is 1500 words. This is a limit, not a quota; concise presentation is a virtue.
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Once again: This is not a required word count. They are the maximum number of words that your marker will read. If you can do it in fewer words without compromising the presentation, please do so.
The report must have a title page with the following items:
Your name
An excellent report will:
Demonstrate a conceptual understanding of all major functions, and how they interact when the program as a whole runs;
Explain your design process, including your assumptions, and the reasons behind choices you made;
Discuss how you tested your program, and in particular why your tests give you confidence that your code is correct; and Be well-formatted without spelling or grammar errors.
Content and Structure
Introduction
If you wish to do so you can write an introduction. In it, give:
A brief overview of your program: how it works; and what it is designed to do.
Content
Talk about why you structured the program the way you did. Below are some questions you could answer:
Program design
Describe what each relevant function does conceptually. (i.e. how does it get you closer to solving the problems outlined in this assignment
How do these functions piece together to make the finished program? Why did you design and implement it this way?
What major design choices did you make regarding the functions that you’ve written, and the overall structure of your program?
For this assignment, you could ask yourself:
How does your AI select a good move?
What data-structures did you choose and why?
How did you develop the AI that is your main submission?
Assumptions
Describe any assumptions that you needed to make, and how they have influenced your design decisions.
How did you test individual functions?
Describe the tests that prove individual functions on their own behave as expected (i.e. testing a function with different inputs and doing a calculation by hand to check that the outputs are correct).
How did you test the entire program? What tests did you perform to show that the program behaves as expected in all (even unexpected) cases?
How did you test the quality of your AI's play?
Inspiration / external content
What resources did you use when writing your program (e.g., published algorithms)?
If you have used resources such as a web-page describing an algorithm, be sure to cite it properly at the end of your report in a ‘References’ section. References do not count to the maximum word limit.
Reflection
Discuss the reasoning behind your decisions, rather than what the decisions were. You can reflect on not only the decisions you made, but the process through which you developed the final program:
Did you encounter any conceptual or technical issues?
If you solved them, describe the relevant details of what happened and how you overcame them.
Sometimes limitations on time or technical skills can limit how much of the assignment can be completed. If you ran into a problem that you could not solve, then your report is the perfect place to describe them. Try to include details such as:
theories as to what caused the problem; suggestions of things that might have fixed it; and discussion about what you did try, and the results of these attempts.
What would you have done differently if you were to do it again?
What changes to the design and structure you would make if you wrote the program again from scratch?
Are parts of the program confusing for the reader? You can explain them in the report (in this situation you should also make use of comments in your code).
If you collaborated with others, what was the nature of the collaboration? (Note that you are only allowed to collaborate by sharing ideas, not code.)
Collaborating is any discussion or work done together on planning or writing your assignment.
Other info
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This is a list of suggestions, not requirements. You should only discuss items from this list if you have something interesting to write.
Things to avoid in a technical report
Line by line explanations of large portions of code. (If you want to include a specific line of code, be sure to format as described in the "Format" section below.)
Pictures of code or VSCodium.
Content that is not your own, unless cited.
Grammatical errors or misspellings. Proof-read it before submission.
Informal language - a technical report is a professional document, and as such should avoid things such as: Unnecessary abbreviations (atm, btw, ps, and so on), emojis, and emoticons; and Recounting events not relevant to the development of the program.
Irrelevant diagrams, graphs, and charts. Unnecessary elements will distract from the important content. Keep it succinct and focused.
If you need additional help with report writing, the academic skills writing centre has a peer writing service and writing coaches.
Format
You are not required to follow any specific style guide (such as APA or Harvard). However, here are some tips which will make your report more pleasant to read, and make more sense to someone with a computer science background.
Colours should be kept minimal. If you need to use colour, make sure it is absolutely necessary.
If you are using graphics, make sure they are vector graphics (that stay sharp even as the reader zooms in on them).
Any code, including type/function/module names or file names, that appears in your document should have a mono-spaced font (such as Consolas, Courier New, Lucida Console, or Monaco).
Other text should be set in serif fonts (popular choices are Times, Palatino, Sabon, Minion, or Caslon). When available, automatic ligatures should be activated.
Do not use underscore to highlight your text.
Text should be at least 1.5 spaced.
Communication
Course staff will not look at assignment code unless it is posted privately in Piazza, or in a drop-in consultation.
Course staff will typically give assistance by asking questions, directing you to relevant exercises from the labs, or definitions and examples from the lectures.
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Submission Advice
Re-read the specification one final time, and make sure you've covered everything.
Confirm that the latest version of your code has been pushed to GitLab by using your browser to visit https://gitlab.cecs.anu.edu.au/uXXXXXXX/assignment3, where XXXXXXX is your student number.
Ensure your program compiles and runs, including the cabal v2-test test suite.
Proof-read and spell-check your report.
Verify that your report is in PDF format, in the root of the project directory (not in src), and named Report.pdf. That capital R is important---Linux uses a case-sensitive file system. Check that you have successfully added it in GitLab.