Project 1: The Game of Hog

5-sided die

I know! I'll use my
Higher-order functions to
Order higher rolls.

Introduction

In this project, you will develop a simulator and multiple strategies for the dice game Hog. You will need to use control statements and higher-order functions together, as described in Sections 1.2 through 1.6 of Composing Programs.

In Hog, two players alternate turns trying to be the first to end a turn with at least 100 total points. On each turn, the current player chooses some number of dice to roll, up to 10. That player's score for the turn is the sum of the dice outcomes.

To spice up the game, we will play with some special rules:

  • Pig Out. If any of the dice outcomes is a 1, the current player's score for the turn is 1.

  • Free Bacon. A player who chooses to roll zero dice scores one more than the largest digit in the opponent's total score.

    • Example 1: If the opponent has 42 points, the current player gains 1 + max(4, 2) = 5 points by rolling zero dice.
    • Example 2: If the opponent has 48 points, the current player gains 1 + max(4, 8) = 9 points by rolling zero dice.
    • Example 3: If the opponent has 7 points, the current player gains 1 + max(0, 7) = 8 points by rolling zero dice.
  • Hogtimus Prime. If a player's score for the turn is a prime number, then the turn score is increased to the next larger prime number. For example, if the dice outcomes sum to 19, the current player scores 23 points for the turn. This boost only applies to the current player. Note: 1 is not a prime number!
  • Hog Wild. If the sum of both players' total scores is a multiple of seven (e.g., 14, 21, 35), then the current player rolls four-sided dice instead of the usual six-sided dice.
  • Hog Tied. If the sum of both players' scores ends in a seven (e.g., 17, 27, 57), then the current player can roll at most one dice.

  • Swine Swap. After the turn score is added, if the current player's total score contains only one unique digit, the players swap total scores.

    • Example 1: The current player has a total score of 13 and the opponent has 91. The current player rolls two dice that total 9. The current player's new total score (22) has only one unique digit (2). These scores are swapped! The current player now has 91 points and the opponent has 22. The turn ends.
    • Example 2: The current player has 88 and the opponent has 42. The current player rolls five dice that total 19, a prime that is boosted to 23 points for the turn. The current player has 111, so the scores are swapped. The opponent ends the turn with 111 and wins the game.

Download starter files

To get started, download all of the project code as a zip archive. You only have to make changes to hog.py.

  • hog.py: A starter implementation of Hog
  • dice.py: Functions for rolling dice
  • hog_gui.py: A graphical user interface for Hog
  • ucb.py: Utility functions for CS 61A
  • ok: CS 61A autograder
  • tests: A directory of tests used by ok
  • images: A directory of images used by hog_gui.py

Logistics

This is a 1-week project. You may work with one other partner. You should not share your code with students who are not your partner or copy from anyone else's solutions.

In the end, you will submit one project for both partners. The project is worth 23 points. 21 points are assigned for correctness, and 2 points for the overall composition of your program.

You will turn in the following files:

  • hog.py

You do not need to modify or turn in any other files to complete the project. To submit the project, run the following command:

python3 ok --submit

You will be able to view your submissions on the OK dashboard.

For the functions that we ask you to complete, there may be some initial code that we provide. If you would rather not use that code, feel free to delete it and start from scratch. You may also add new function definitions as you see fit.

However, please do not modify any other functions. Doing so may result in your code failing our autograder tests. Also, please do not change any function signatures (names, argument order, or number of arguments).

Testing

Throughout this project, you should be testing the correctness of your code. It is good practice to test often, so that it is easy to isolate any problems. However, you should not be testing too often, to allow yourself and your partner the time to think through problems.

We have provided an autograder called ok to help you with testing your code and tracking your progress. The first time you run the autograder, you will be asked to log in with your OK account using your web browser. Please do so. Each time you run ok, it will back up your work and progress on our servers.

The primary purpose of ok is to test your implementations, but there are two things you should be aware of.

First, some of the test cases are locked. To unlock tests, run the following command from your terminal:

python3 ok -u

This command will start an interactive prompt that looks like:

=====================================================================
Assignment: The Game of Hog
OK, version ...
=====================================================================

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Unlocking tests

At each "? ", type what you would expect the output to be.
Type exit() to quit

---------------------------------------------------------------------
Question 0 > Suite 1 > Case 1
(cases remaining: 1)

>>> Code here
?

At the ?, you can type what you expect the output to be. If you are correct, then this test case will be available the next time you run the autograder.

The idea is to understand conceptually what your program should do first, before you start writing any code.

Once you have unlocked some tests and written some code, you can check the correctness of your program using the tests that you have unlocked:

python3 ok

Most of the time, you will want to focus on a particular question. Use the -q option as directed in the problems below.

Second, some of the test cases are hidden. These test cases are not run by the command:

python3 ok

They are only run when you submit:

python3 ok --submit

Because of this, we recommend that you submit after you finish each problem. Only your last submission will be graded. It is also useful for us to have more backups of your code in case you run into a submission issue.

After you run this command, you will receive an email (to the address that you used to sign up for OK) that has the output from all failed unlocked tests, including hidden tests, along with your score at the bottom. You can continue submitting until you pass all the tests. However, you will receive at most one email every half hour.

This buffer period is meant for you and your partner to try and understand where your error comes from, and take some time to think through your code. We encourage you to do this for all projects.

The tests folder is used to store autograder tests, so do not modify it. You may lose all your unlocking progress if you do. If you need to get a fresh copy, you can download the zip archive and copy it over, but you will need to start unlocking from scratch.

Graphical User Interface

A graphical user interface (GUI, for short) is provided for you. At the moment, it doesn't work because you haven't implemented the game logic. Once you complete the play function, you will be able to play a fully interactive version of Hog!

In order to render the graphics, make sure you have Tkinter, Python's main graphics library, installed on your computer. Once you've done that, you can run the GUI from your terminal:

python3 hog_gui.py

Once you complete the project, you can play against the final strategy that you've created!

python3 hog_gui.py -f

Phase 1: Simulator

In the first phase, you will develop a simulator for the game of Hog.

Problem 0 (1 pt)

The dice.py file represents dice using non-pure zero-argument functions. These functions are non-pure because they may have different return values each time they are called. The documentation of dice.py describes the two different types of dice used in the project:

  • Dice can be fair, meaning that they produce each possible outcome with equal probability. Examples: four_sided, six_sided.
  • For testing functions that use dice, deterministic test dice always cycle through a fixed sequence of values that are passed as arguments to the make_test_dice function.

Before we start writing any code, let's understand the make_test_dice function by unlocking its tests.

python3 ok -q 00 -u

This should display a prompt that looks like this:

=====================================================================
Assignment: Project 1: Hog
OK, version v1.5.2
=====================================================================

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Unlocking tests

At each "? ", type what you would expect the output to be.
Type exit() to quit

---------------------------------------------------------------------
Question 0 > Suite 1 > Case 1
(cases remaining: 1)

>>> test_dice = make_test_dice(4, 1, 2)
>>> test_dice()
?

You should type in what you expect the output to be. To do so, you need to first figure out what test_dice will do, based on the description above.

You can exit the unlocker by typing exit() (without quotes). Typing Ctrl-C on Windows to exit out of the unlocker has been known to cause problems, so avoid doing so.

Problem 1 (2 pt)

Implement the roll_dice function in hog.py. It takes two arguments: a positive integer giving the number of dice to roll, num_rolls, and a dice function. It returns the number of points scored by rolling that number of dice simultaneously: either the sum of the outcomes or 1 (Pig Out).

To obtain a single outcome of a dice roll, call dice(). You must call the dice function exactly the number of times specified by the first argument (even if a 1 is rolled) since we are rolling all dice simultaneously in the game (otherwise tests and the GUI will fail).

Before writing any code, unlock the tests to verify your understanding of the question.

python3 ok -q 01 -u

Once you are done unlocking, begin implementing your solution. You can check your correctness with:

python3 ok -q 01

The roll_dice function has a default argument value for dice that is a random six-sided dice function. The tests use fixed dice.

Problem 2 (2 pt)

Implement the take_turn function, which returns the number of points scored for a turn by the current player. Your implementation should call roll_dice when possible.

You will need to implement the Free Bacon rule. You can assume that opponent_score is less than 100. For a score less than 10, assume that the first of the two digits is 0. Implement the free_bacon helper function, and use it in your implementation when possible.

You will also need to implement the Hogtimus Prime rule, which applies to both regular turns and Free Bacon turns! To implement Hogtimus Prime, write your own prime functions above the take_turn function. One way to do so is to write two functions, is_prime and next_prime. There are no tests for is_prime and next_prime, but you can test them on your own using doctests that you create. Remember, 1 isn't prime!

Before writing any code, unlock the tests to verify your understanding of the question.

python3 ok -q 02 -u

Once you are done unlocking, begin implementing your solution. You can check your correctness with:

python3 ok -q 02

Problem 3 (1 pt)

Implement the select_dice and max_dice functions, which help enforce the Hog Wild and Hog Tied special rules, respectively.

select_dice takes two arguments: the scores for the current and opposing players. It returns the dice to be used for the turn: either four_sided or six_sided. max_dice takes the same arguments and returns the maximum number of dice a player can roll.

Before writing any code, unlock the tests to verify your understanding of the question.

python3 ok -q 03 -u

Once you are done unlocking, begin implementing your solution. You can check your correctness with:

python3 ok -q 03

Problem 4 (1 pt)

To help you implement the Swine Swap rule, write a function called is_swap that checks to see if the current score contains only one unique digit.

Before writing any code, unlock the tests to verify your understanding of the question.

python3 ok -q 04 -u

Once you are done unlocking, begin implementing your solution. You can check your correctness with:

python3 ok -q 04

Problem 5 (3 pt)

Implement the play function, which simulates a full game of Hog. Players alternate turns, each using their respective strategy function (Player 0 uses strategy0, etc.), until one of the players reaches the goal score. When the game ends, play returns the final total scores of both players, with Player 0's score first, and Player 1's score second.

Here are some hints:

  • You should use the functions you have already written! You will need to call take_turn with all three arguments.
  • Enforce all the remaining special rules: Hog Tied, Hog Wild, and Swine Swap.
  • You can get the number of the other player (either 0 or 1) by calling the provided function other.
  • A strategy is a function that, given a player's score and their opponent's score, returns how many dice the player wants to roll. A strategy function (such as strategy0 and strategy1) takes two arguments: scores for the current player and opposing player, which both must be non-negative integers. A strategy function returns the number of dice that the current player wants to roll in the turn. Each strategy function should be called only once per turn. Don't worry about the details of implementing strategies yet. You will develop them in Phase 2.

Before writing any code, unlock the tests to verify your understanding of the question.

python3 ok -q 05 -u

Once you are done unlocking, begin implementing your solution. You can check your correctness with:

python3 ok -q 05

The last test for Question 5 is a fuzz test, which checks that your play function works for a large number of different inputs. Failing this test means something is wrong, but you should look at other tests to see where the problem might be.

Hint: If you fail the fuzz test, check that you're only calling take_turn once per turn!

Once you are finished, you will be able to play a graphical version of the game. We have provided a file called hog_gui.py that you can run from the terminal:

python3 hog_gui.py

If you don't already have Tkinter (Python's graphics library) installed, you'll need to install it first before you can run the GUI.

The GUI relies on your implementation, so if you have any bugs in your code, they will be reflected in the GUI. This means you can also use the GUI as a debugging tool; however, it's better to run the tests first.

Congratulations! You have finished Phase 1 of this project!

Phase 2: Strategies

In the second phase, you will experiment with ways to improve upon the basic strategy of always rolling a fixed number of dice. First, you need to develop some tools to evaluate strategies.

Problem 6 (1 pt)

Implement the check_strategy function decorator, which takes a strategy function as an argument and returns the same strategy function. It calls the strategy with all valid inputs and verifies that the strategy always returns a valid output. The provided check_strategy_roll function will raise an error with a helpful message if num_rolls is an invalid output.

Before writing any code, unlock the tests to verify your understanding of the question.

python3 ok -q 06 -u

Once you are done unlocking, begin implementing your solution. You can check your correctness with:

python3 ok -q 06

Problem 7 (2 pt)

Implement the make_averaged function, which is a higher-order function that takes a function fn as an argument. It returns another function that takes the same number of arguments as fn (the function originally passed into make_averaged). This returned function differs from the input function in that it returns the average value of repeatedly calling fn on the same arguments. This function should call fn a total of num_samples times and return the average of the results.

To implement this function, you need a new piece of Python syntax! You must write a function that accepts an arbitrary number of arguments, then calls another function using exactly those arguments. Here's how it works.

Instead of listing formal parameters for a function, we write *args. To call another function using exactly those arguments, we call it again with *args. For example,

>>> def printed(fn):
...     def print_and_return(*args):
...         result = fn(*args)
...         print('Result:', result)
...         return result
...     return print_and_return
>>> printed_pow = printed(pow)
>>> printed_pow(2, 8)
Result: 256
256
>>> printed_abs = printed(abs)
>>> printed_abs(-10)
Result: 10
10

Read the docstring for make_averaged carefully to understand how it is meant to work.

Before writing any code, unlock the tests to verify your understanding of the question.

python3 ok -q 07 -u

Once you are done unlocking, begin implementing your solution. You can check your correctness with:

python3 ok -q 07

Problem 8 (2 pt)

Implement the max_scoring_num_rolls function, which runs an experiment to determine the number of rolls (from 1 to 10) that gives the maximum average score for a turn. Your implementation should use make_averaged and roll_dice.

If two numbers of rolls are tied for the maximum average score, return the lower number. For example, if both 3 and 6 achieve a maximum average score, return 3.

Before writing any code, unlock the tests to verify your understanding of the question.

python3 ok -q 08 -u

Once you are done unlocking, begin implementing your solution. You can check your correctness with:

python3 ok -q 08

To run this experiment on randomized dice, call run_experiments using the -r option:

python3 hog.py -r

Running experiments For the remainder of this project, you can change the implementation of run_experiments as you wish. By calling average_win_rate, you can evaluate various Hog strategies. For example, change the first if False: to if True: in order to evaluate always_roll(8) against the baseline strategy of always_roll(6). You should find that it loses more often than it wins, giving a win rate below 0.5.

Some of the experiments may take up to a minute to run. You can always reduce the number of samples in make_averaged to speed up experiments.

Problem 9 (1 pt)

A strategy can take advantage of the Free Bacon rule by rolling 0 when it is most beneficial to do so. Implement bacon_strategy, which returns 0 whenever rolling 0 would give at least margin points and returns num_rolls otherwise. Don't forget about the Hogtimus Prime rule!

Before writing any code, unlock the tests to verify your understanding of the question.

python3 ok -q 09 -u

Once you are done unlocking, begin implementing your solution. You can check your correctness with:

python3 ok -q 09

Once you have implemented this strategy, change run_experiments to evaluate your new strategy against the baseline. You should find that it wins more than half of the time.

Problem 10 (2 pt)

A strategy can also take advantage of the Swine Swap rule. The swap_strategy rolls 0 if it would cause a beneficial swap. It also returns 0 if rolling 0 would give at least margin points and would not cause a swap. Otherwise, the strategy rolls num_rolls.

Before writing any code, unlock the tests to verify your understanding of the question.

python3 ok -q 10 -u

Once you are done unlocking, begin implementing your solution. You can check your correctness with:

python3 ok -q 10

Once you have implemented this strategy, update run_experiments to evaluate your new strategy against the baseline. You should find that it gives a significant edge over always_roll(6).

At this point, run the entire autograder to see if there are any tests that don't pass.

python3 ok

Problem 11 (3 pt)

Implement final_strategy, which combines these ideas and any other ideas you have to achieve a win rate of at least 0.70 (for full credit) against the baseline always_roll(6) strategy. Partial credit is also given if you are close. Some suggestions:

  • swap_strategy is a good default strategy to start with.
  • There's no point in scoring more than 100. Check for chances to win.
  • Don't swap scores when you're winning.
  • Try to force a beneficial swap at all costs.
  • It can be advantageous to trigger Hog Tied for your opponent. (Note: Trying to trigger Hog Tied at all costs may not be as beneficial as rolling the dice.)
  • Choose the num_rolls and margin arguments carefully. Depending on whether you are Hog Tied or Hog Wild, you may want to have a different num_rolls and margin.
  • If you are in the lead, you might take fewer risks.

You can check your final strategy win rate by running OK.

python3 ok -q 11

You can also play against your final strategy with the graphical user interface:

python3 hog_gui.py -f

The GUI will alternate which player is controlled by you.

Congratulations, you have reached the end of your first CS 61A project!