Cody Boone Ferguson
af5482825c
The sections have been modified a fair amount. The Entries menu has been extended to have: Fixing entries, Updating author info, Thanks for the help. The first two were moved from FAQ and the last one from About. The rationale for these, in order: entries and authors have to do with entries and most of the help involves entries. It also has to do with website but in 'about' it does not seem the right place, unless maybe it is renamed to 'Credits' or something (I am not suggesting this one way or the other). This one is debatable but that was the rationale. The Status menu has been extended to have: Markdown guidelines and Security policy. The rationale is that the markdown guidelines are part of contest guidelines and the security policy is about the status of the entries and how if there are any security problems they will not be addressed (instead of about the IOCCC). The FAQ was extended to have: Compiling entries, Running entries, How to help. The reason to not have compiling and running entries under Entries is because this is 'how to' and also the menu was too long. How to help seems like a good idea under FAQ too (was in About). About was extended to have the new 'about.html' page (from about.md). This is a rare case where a new file is useful as it fits under 'About'. The menu now is: Home page, About the IOCCC, The Judges, Contact us. I was pondering the 'About [the IOCCC]' at the top and also naming it 'About us' but it seemed like a link to index.html was necessary and as for 'about us' it seemed less clear as to whether it was about the judges or the contest itself. The FAQ has been updated slightly for this. After further inspection the bin/index.html and the inc/index.html links were removed from the about section. With these changes, renaming an item or slight reordering notwithstanding, I believe that #2006 is probably in good shape.
To build:
make
Bugs and (Mis)features:
The current status of this entry is:
STATUS: INABIAF - please DO NOT fix
For more detailed information see 2015/hou in bugs.html.
To use:
echo something | ./prog
./prog < file
Try:
./try.sh
Judges' remarks:
A good start for understanding this entry might be rfc1321.txt. How does it compute this using only a single looping construct? The original reference source code for this algorithm is about 355 lines of code, yet this entry is only 199 lines with one statement per line and it isn't using lots of macro expansion tricks like the reference code!
Some things that make you go, "huh?"
./prog < prog.c | cut -c-5
./prog < Makefile | cut -c-4
How are those values magically returned?
What happens with a large file? Something over 256K.
./prog < large_file
Where does that message come from?
Author's remarks:
This looks like a normal C program.
Almost everything is a double.
There are tell-tale signs like pow(2,(?/12)) and exp(-?*?) (names redacted).
You can also find a bunch of cosines and polynomial evaluations.
It looks like a ????? ???????????, right?
Run and find out.
Why obfuscated
Some poor scripting folks only have access to doubles (Jav?script, L?a, BA?IC, etc.).
As a C programmer, I feel obliged to show a gesture of sympathy, to experience their pain and provide an answer.
Except when absolutely necessary (printf, int main(), array indexing), there
isn't a single integer. Even getchar() and EOF are immediately converted.
Since bool counts as an integer type too, there is no boolean either. No
comparison, no if, no ?:, no || &&. Everything is done in a single loop
that terminates on printf(3). Straight up arithmetic.
floor(3) and ceil(3) are technically double-to-double functions, but they feel
like cheating. Yes cos(3), no floor(3).
Limitations
Hard requirements:
-
The platform must implement the
doubletype as IEEE754-compliant 64-bit floating point numbers. The 80-bit intermediate format used by x87 is considered as an violation of this. The code should print an error message on such platforms. -
The program must start with the CPU / FPU in round-to-nearest mode.
Soft requirements:
-
The compiler must respect
volatile. The code is formatted to warn about that, though. -
The printed result is only correct on little-endian machines. The program takes care to warn about this issue after printing an incorrect big-endian result. Error messages become garbled, though.
Tested platforms:
- Linux 3.18.7, Rasperberry Pi 2, clang 3.0-6.2, (works)
- Linux 3.18.7, Rasperberry Pi 2, gcc 4.6.3, (works)
- Mac OS X 10, x64, Apple LLVM version 6.1.0 (clang-602.0.53), (works)
- Windows 8.1, x86, MSVC 2012 (works)
- Windows 8.1, x64, MSVC 2012 (works)
- Windows 8.1, x86, MinGW gcc 4.6.2 (fails, prints error message)
- Windows 8.1, x86, MinGW gcc 4.6.2 with -msse2 -mfpmath=sse (works)