Most unstable

Edward Giles

Judges' comments:

To use:

sudo apt install libsdl2-dev  # Linux
Something else # MacOS
make
./prog

Try:

./prog ioccc.txt
./prog prog.c

Selected Judges Remarks:

Can you explain the behavior of the program when ioccc.txt is given to it as input?

How would the description of the state machine look like when translated from Polynomish to English?

Author’s comments:

Remarks

This entry graphically displays a simulation of sand falling. It uses SDL to draw the interface.

The code makes the following assumptions about the underlying system:

SDL 2 is installed from https://libsdl.org
“double” is an IEEE 754 floating-point type and sizeof(double)==8
The compiler supports the C99 standard

In order to simulate the motion of the sand, a cellular automaton is used. The state transition table is not stored directly. Instead, the program stores the coefficients of a polynomial that map each state to the correct one. These coefficients are stored as raw hexadecimal in the V[] array, and they are reinterpreted as doubles when used. This allows more numeric precision in fewer characters (base 16 > base 10), and makes the purpose of the array less clear.

The code is laid out graphically as a bucket pouring sand, and it is far easier to observe this high-level layout than the code’s actual function.

The preprocessor is used to both obfuscate the code as a whole and abbreviate the calls to SDL. Additionally, throughout the code, the variables were named so that they are short and easily confused with each other.