Description

Aims
to give you experience writing MIPS assembly code to give you experience with data and control structures in MIPS
Getting Started
Create a new directory for this assignment called cellular, change to this directory, and fetch the provided code by running these commands:
$ mkdir cellular $ cd cellular $ 1521 fetch cellular
This will add the following files into the directory:
cellular.c: a cellular automaton renderer cellular.s: a stub assembly file to complete
cellular.c: A Cellular Automaton Renderer
cellular.c is an implementation of a one-dimensional, three-neighbour cellular automaton. It examines its neighbours and its value in the previous generation to derive the value for the next generation.
. . . . # . . . .
. . . # # # . . .
. . # # . . # . .
. # # . # # # # .
# # . . # . . . #
Here, we using ‘#’ to indicate a cell that’s alive; and ‘.’ to indicate a cell that is not.
Given we examine three neighbours, there are eight states that the prior cells could be in. They are:
# # #
7

# # #
.
# # .
6

# # .
.
. . . . . # . # . . # # # . . # . #
0 1 2 3 4 5
. . . . . # . # . . # # # . . # . #
. # # # # .
For each one, we decide what action to take. For example, we might choose to have the following ‘rule’:
We apply this rule to every cell, to determine whether the next state is alive or dead; and this forms the next generation. If we print these generations, one after the other, we can get some interesting patterns.
The description of the rule above — by example, showing each case and how it should be handled — is inefficient. We can abbreviate this rule by reading it in binary, considering live cells as 1’s and dead cells as 0s; and if we consider the prior states to be a binary value too — the above rule could be 0b00011110, or 30.
To use that rule, we would mix together the previous states we’re interested in — left, middle, and right — which tells us which bit of the rule value gives our next state.
The size of a generation, the rule number, and the number of generations are supplied on standard input. For example:
$ ./cellular
Enter world size: 60
Enter rule: 30
Enter how many generations: 10
0 …………………………#………………………..
1 ………………………..###……………………….
2 ……………………….##..#………………………
3 ………………………##.####……………………..
4 ……………………..##..#…#…………………….
5 …………………….##.####.###……………………
6 ……………………##..#….#..#…………………..
7 …………………..##.####..######………………….
8 ………………….##..#…###…..#…………………
9 …………………##.####.##..#…###………………..
10 ………………..##..#….#.####.##..#……………….
If generations is a negative number, the generations should be printed in reverse.
$ ./cellular
Enter world size: 60
Enter rule: 30
Enter how many generations: -10
10 ………………..##..#….#.####.##..#……………….
9 …………………##.####.##..#…###………………..
8 ………………….##..#…###…..#…………………
7 …………………..##.####..######………………….
6 ……………………##..#….#..#…………………..
5 …………………….##.####.###……………………
4 ……………………..##..#…#…………………….
3 ………………………##.####……………………..
2 ……………………….##..#………………………
1 ………………………..###……………………….
0 …………………………#………………………..
cellular.s: The Assignment
Your task in this assignment is to implement cellular.s in MIPS assembler.
You have been given some assembly and helpful information in cellular.s. Read through the provided code carefully, then add MIPS assembly so it executes exactly the same as cellular.c.
$ 1521 spim -f cellular.s
Loaded: /home/cs1521/share/spim/exceptions.s
Enter world size: 60
Enter rule: 30
Enter how many generations: 10
0 …………………………#………………………..
1 ………………………..###……………………….
2 ……………………….##..#………………………
3 ………………………##.####……………………..
4 ……………………..##..#…#…………………….
5 …………………….##.####.###……………………
6 ……………………##..#….#..#…………………..
7 …………………..##.####..######………………….
8 ………………….##..#…###…..#…………………
9 …………………##.####.##..#…###………………..
10 ………………..##..#….#.####.##..#……………….
To test your implementation, you can compile the provided C implementation, run it to collect the expected output, run your assembly implementation to collect observed output, and then compare them — for example:
$ dcc cellular.c -o cellular
$ parameters=”20 15 5″
$ echo $parameters|./cellular|tee c.out 0 ……….#………
1 ###########.######## 2 #………..#…….
3 #.###########.###### 4 #.#………..#…..
5 #.#.###########.####
$ echo $parameters|1521 spim -f cellular.s|sed 1d|tee mips.out 0 ……….#………
1 ###########.######## 2 #………..#…….
3 #.###########.###### 4 #.#………..#…..
5 #.#.###########.#### $ diff -s c.out mips.out
Files c.out and mips.out are identical
Try this for different values of the parameters.
Assumptions and Clarifications
Like all good programmers, you should make as few assumptions as possible.
There will be a style penalty for assignments that do not use the stack to save and restore $ra (in main)
There will be a style penalty for assignments that do not follow these important MIPS calling conventions:
function arguments should be passed in $a0 through $a3
$s0..$s9 should be preserved across function calls: if a function changes these registers, it must restore the original value before returning
The above two style penalties apply only to assignments which score above CR (65+) on performance testing.
If you need clarification on what you can and cannot use or do for this assignment, ask in the class forum.
You are required to submit intermediate versions of your assignment. See below for details.
Change Log
Version 1.0
Version 1.0.1
Version 1.0.2
Version 1.0.3
Version 1.0.4 cellular.c: MIN_RULE is 0.
When you think your program is working, you can use autotest to run some simple automated tests:
$ 1521 autotest cellular

Submission
When you are finished working on the assignment, you must submit your work by running give:
$ give cs1521 ass1_cellular cellular.s
You can run give multiple times. Only your last submission will be marked.
If ki t h fi d it i t t l d k i i ‘ b i t f
You check the files you have submitted here.
Assessment Scheme
This assignment will contribute 15 marks to your final COMP1521 mark.
80% of the marks for assignment 1 will come from the performance of your code on a large series of tests.
20% of the marks for assignment 1 will come from hand marking. These marks will be awarded on the basis of clarity, commenting, elegance and style. In other words, you will be assessed on how easy it is for a human to read and understand your program.
HD (85+) beautiful documented code, which uses the stack with MIPS calling conventions, and implements spec perfectly
DN (75+) very readable code, prints cells correctly if n_generations positive or negative, all rules correctly handled
CR (65+) readable code, prints cells correctly if n_generations positive, rules mostly working
PS (55+) prints initial world (first line) correctly and sometimes more correct lines
PS (50+) good progress on assignment but not passing autotests
0% knowingly providing your work to anyone and it is subsequently submitted (by anyone).
0 FL for
COMP1521 submitting any other person’s work; this includes joint work.
academic submitting another person’s work without their consent; misconduct paying another person to do work for you.
Intermediate Versions of Work
You are required to submit intermediate versions of your assignment.
Every time you work on the assignment and make some progress you should copy your work to your CSE account and submit it using the give command below. It is fine if intermediate versions do not compile or otherwise fail submission tests. Only the final submitted version of your assignment will be marked.
All these intermediate versions of your work will be placed in a Git repository and made available to you via a web interface at https://gitlab.cse.unsw.edu.au/z5555555/20T2-comp1521-ass1_cellular (replacing z5555555 with your own zID). This will allow you to retrieve earlier versions of your code if needed.
Attribution of Work
This is an individual assignment.
The work you submit must be entirely your own work, apart from any exceptions explicitly included in the assignment specification above. Submission of work partially or completely derived from any other person or jointly written with any other person is not permitted.
Assignment submissions will be examined, both automatically and manually, for such submissions.

For all enquiries, please email the class account at cs1521@cse.unsw.edu.au
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