Program 1 - Conway's Game of Life

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Introduction

In this programming assignment, we are going to explore a classic in Computer Science! This is Conway's Game of of life. It will be a good practice for using vectors, as well as making use of our nice termmanip.h library.

Conway's game of life was created by John Conway, a British mathematician, some time in the 1970's. It was an example of a problem first proposed by John Von Neumann (creator of the famous computer architecture). Von Neumann's problem was in the study of self-replicating machines. This proposal led Conway to create this little game, which is one of the first examples of a field called cellular automata (CA).

The basic idea of a CA is to use a simple set of rules to create a very complex pattern. Don't be fooled by the easiness of understanding the rules. Conway's game of life, when played on an infinite grid, is capable of simulating a Turing machine. This means that the simple rules we are about to look at are capable of universal computation. In fact, randomly generated rule sets have a fairly high probability of being capable of universal computation. Maybe the universe is geared toward forming computers!

The Game of Life

Conway's game of life is played on an orthogonal grid. Each element in the grid is a cell, and the cell is either alive or dead. Each grid arrangement is used to generate the next "generation" of cells. The fate of each cell is determined by it's neighbors. Take for instance, the cell 0. The X's are it's neighbors:

XXX
X0X
XXX

So each cell has 8 neighboring cells. The number of living neighbors surrounding a cell are what determines what the cell does in the next generation. The rules that the game follows are:

  1. A living cell with fewer than 2 living neighbors dies. (Starvation)
  2. A living cell with more than 3 living neighbors dies. (Overcrowding)
  3. A living cell with 2 or 3 living neighbors lives on. (Stability)
  4. A dead cell with exactly 3 living neighbors will become a live cell (Reproduction)

So you can see that counting the cells around each cell, plus that cell's state, determines what the cell does. Generally, this results in weird and wonderful patterns. There are some patterns that are interesting, however. Take for instance:

***

Following those rules, there are two possible iterations which this oscillates through.

*** Followed by:

*
*
*

Then:

*** And so on. This is called a spinner. The next interesting one is the glider. Use a sheet of paper and checkout what the glider does:

 *
  *
***
 

The glider moves! How cool is that?

There are some other interesting shapes, and a few are included with the assignment Director. That way you can run them through your own programs.

So now, we want to program this thing!

What follows is a specification of the program as well as some ideas to get you started.

Programming the Game of Life

Our program will be called "life". It can be invoked in one of two ways. The first way is like so:

 ./life

This will cause the program to start with a random grid, and then begin executing the rules.

The other way of invoking the program is as:

 ./life filename

Where it loads the grid from the filename.

Remember how files worked from last semester? Also you'll need to remember the command line argument handling from Lab 1. (You maybe even want to copy and paste that little function I gave you!)

Be sure to test your program in both random mode and in the files included in your directory.

  • spinner
  • glider
  • gosper-gun

The grid is displayed on the screen, with a "*" for a living cell and a space " " for a dead cell.

Some Tips

  • We will assume that we are playing on an 80x24 grid.
  • I made a cell class and a grid class.
  • My grid class contains a vector of vectors to form the grid.
  • My grid class contains a count neighbor function.
  • My grid class contains an update function which does the following


1.  Update the living status of each cell. (Which entity does this
    is a tricky point of concern\!)
2.  Count the living neighbors of each cell and notify the cell of
    the living status.
3.  Display the grid
  • Your main function should load either a random grid or a grid contained in a file.
  • After loading from the grid your program should enter an infinite loop which consists of updating the grid and then using usleep (see "man usleep" for more information) to delay between each frame.

The biggest tip is this. Asking yourself the right questions is the most important thing you can do. Try designing first and then coding, and then identify additional questions that come up. Keep that conversation between yourself and your code going, and you can write any program I throw at you!

Also, talk to each other. Talk to rubber ducks (that's a real method). Draw pictures on windows with crayon. Do whatever you have to do to tease out all of the detail and enjoy and savor the complexity that you create.

Notes

Handwritten notes are important! Here are the ones I drew up before writing even one line of code:


LifeNotes.jpg