Items tagged c in 2024
Filters: Year: 2024 × c × Sorted by date
Tagged Pointer Strings (2015) (via) Mike Ash digs into a fascinating implementation detail of macOS.
Tagged pointers provide a way to embed a literal value in a pointer reference. Objective-C pointers on macOS are 64 bit, providing plenty of space for representing entire values. If the least significant bit is 1 (the pointer is a 64 bit odd number) then the pointer is "tagged" and represents a value, not a memory reference.
Here's where things get really clever. Storing an integer value up to 60 bits is easy. But what about strings?
There's enough space for three UTF-16 characters, with 12 bits left over. But if the string fits ASCII we can store 7 characters.
Drop everything except a-z A-Z.0-9 and we need 6 bits per character, allowing 10 characters to fit in the pointer.
Apple take this a step further: if the string contains just eilotrm.apdnsIc ufkMShjTRxgC4013 ("b" is apparently uncommon enough to be ignored here) they can store 11 characters in that 60 bits! # 8th May 2024, 2:23 pm
I’m writing a new vector search SQLite Extension. Alex Garcia is working on sqlite-vec, a spiritual successor to his sqlite-vss project. The new SQLite C extension will have zero other dependencies (sqlite-vss used some tricky C++ libraries) and will work using virtual tables, storing chunks of vectors in shadow tables to avoid needing to load everything into memory at once. # 3rd May 2024, 3:16 am
llm.c (via) Andrej Karpathy implements LLM training—initially for GPT-2, other architectures to follow—in just over 1,000 lines of C on top of CUDA. Includes a tutorial about implementing LayerNorm by porting an implementation from Python. # 9th April 2024, 3:24 pm
Hello World (via) Lennon McLean dives deep down the rabbit hole of what happens when you execute the binary compiled from “Hello world” in C on a Linux system, digging into the details of ELF executables, objdump disassembly, the C standard library, stack frames, null-terminated strings and taking a detour through musl because it’s easier to read than Glibc. # 9th April 2024, 1:06 am
Building and testing C extensions for SQLite with ChatGPT Code Interpreter
I wrote yesterday about how I used Claude and ChatGPT Code Interpreter for simple ad-hoc side quests—in that case, for converting a shapefile to GeoJSON and merging it into a single polygon.
[... 4612 words]Beej’s Guide to Networking Concepts (via) Beej’s Guide to Network Programming is a legendary tutorial on network programming in C, continually authored and updated by Brian “Beej” Hall since 1995.
This is NOT that. Beej’s Guide to Networking Concepts is brand new—started in March 2023—and illustrates a whole bunch of networking concepts using Python instead of C.
From the forward: “Is it Beej’s Guide to Network Programming in Python? Well, kinda, actually. The C book is more about how C’s (well, Unix’s) network API works. And this book is more about the concepts underlying it, using Python as a vehicle.” # 30th January 2024, 10:08 pm
Find a level of abstraction that works for what you need to do. When you have trouble there, look beneath that abstraction. You won’t be seeing how things really work, you’ll be seeing a lower-level abstraction that could be helpful. Sometimes what you need will be an abstraction one level up. Is your Python loop too slow? Perhaps you need a C loop. Or perhaps you need numpy array operations.
You (probably) don’t need to learn C.
— Ned Batchelder # 24th January 2024, 6:25 pm