# CSCI 247 Homework 3 : Game of Life solution

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## Description

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In this homework assignment you will interface with a cellular automation simulator. The rules are
very simple. The board is a grid. Each grid square can hold at most one cell. For a cell to survive from
generation to the next, it needs two or three neighbors. Too many neighbors cause the cell to starve.

Too few neighbors causes an incurable case of ennui. All is not lost. If a grid square has exactly three
neighbors, a new cell is born, which is kind of strange when you think about it.

In this simulation, a grid square that includes a cell is marked as 1, and 0 otherwise. For example
0 0 0 1
0 1 0 1
0 0 0 1
1 0 1 1

would represent a 16 square grid, with 7 cells, where the underlined cell has no neighbors.
There are many variations on this game, which is Conway’s Game of Life and is a B3/S23 game. That is,
cells survive with two or three neighbors and are born with exactly 3 neighbors. This game is can be
extended into the real domain or more dimensions. However, we will stick with the original B3/S23.

You are being given a very naive evolution implementation called evolve. It works, but it is slow. See
how fast you can make it run (we’ve discussed optimization techniques).

Outcomes: Understand and apply the loop and other optimizations we discussed, including:
• Remove loop inefficiencies and reduce procedure calls
• Reduce unnecessary memory references and loop unrolling

You CAN work in groups of 2 in completing this assignment. In that case, only a single person
uploads .c files to Canvas, and the names of both people should be in the header of each file.
The instructions in this document are meant to be executed on the lab machines (you need to ssh in).
If you want to work on your personal machine, see section Working on your personal computer.

## Details

The experimental set-up is implemented in a library called liblife.a. Since it has solutions (different types
of evolve), it is a binary, which is saved to /home/jagodzf/lib. A provided Makefile and life.c
are available at the following, which you should retrieve.

/home/jagodzf/public_html/teaching/csci247/homeworks/hw3-gameOfLife

There are multiple ways to run the simulation/test program.
• Silent mode. The program runs the test cases against the provided evolve methods for 500
generations. It then reports the average performance of each method. The performance value
is an equation that considers memory moves, efficiency, memory accesses, etc. A low value
performance measure specifies that fewer resources were needed to run the program. Hence, a
lower performance value is preferred. This is the default mode.

• Full GUI mode. The simulator will attempt to open a new WINDOW showing the simulation
running. If you are connecting via SSH to the CS computers, you must export your view. This is
invoked via -fg.

• Lazy GUI mode. This is a command-line version of the GUI, that does not open a new WINDOW
(hence is suitable for invoking via SSH). This will print the top-left 10 x 10 cells of the 1024 x
1024 grid for each generation. Invoke via -lg.

For example, compiling and invoking via the simple GUI mode:
\$ make
\$ ./life -lg
All invocations will print the generation number, as well as the final stats for each implementation of the
evolve method.

Makefile references lib and include in the jagodzf directory, so if you want to build the
executable on your personal computer, you’ll need to modify Makefile to direct it to the local locations
of lib and include.

• Improve the performance of the simulation by modifying the evolve method. Do this by
implementing various optimization techniques. Refer to the lecture slides.
• You can modify any code in life.c, but make sure your edits don’t break the simulation run.
“Simple” with your userID, so that when the program runs, it might print the following:
jagodzf: 5.61
jobss: 27.22
gatesb: 16.44
turinga: 10.68
lovelaa: 7.37

Hints and suggestions
• You are free to add as many test methods as you want, and you are encouraged to do this. Copy
the code, give it a new name, and add the new evolve method to the test harness (e.g,
add_method). This will let you see if you are making improvements.

Your implementation will be evaluated against Simple, jobs, gatesb, turinga, and lovelaa. It will be tested
using the silent (default) mode.

Rubric and Submission
Upload your life.c file to Canvas. If for some reason you also develop other (custom) .c and .h files,