Fun fact, this "world's most complicated/important machine" that Veritasium just covered runs C++! youtu.be/MiUHjLxm3V0 I know because I have had students from ASML on multiple occasions (they had me out there for training and to speak at a meetup back in 2018!) @veritasium.bsky.social

I just rediscovered that I have a Wikipedia page.... But only in German(!). Not quite sure how that came to be so...

The music for the Advent of Code Optimisation is available for you listening pleasure: youtu.be/6ZlVRMkFB9c?... and check out nocturnalplant's bandcamp too: nocturnalplant.bandcamp.com/music Thanks @nocturnalplant.bsky.social !

6:00 Added the missing -O2 flag. Lovely vid!

My first CYO @effinbirds.com of the year. Asked the spouse for the adjective without context. Feel it's an accurate description of the news this morning.

I am delighted to announce the release of my latest project: Fully documented source code for The Sentinel, Geoff Crammond’s 1986 masterpiece. Here’s the repository; deep dives coming soon. See thread for details. 1/9 github.com/markmoxon/th... #retrocomputing #retrogaming #bbcmicro #c64 #8bit

For your viewing pleasure, some outtakes from the #AoCO2025 - see some of how the sausage was made! youtu.be/8gASKxx6mCc?...

Thanks to my Advent of Code Optimisation #AoCO2025 Compiler Explorer's shop sales have raised $1,780! Huge thanks to all who bought mugs, t shirts, desk mats and hoodies!! Order yours: shop.compiler-explorer.com I'll do a detailed breakdown of CE costs soon. Thanks everyone and Happy New Year!

I tried to sell my last generation @Garmin.com watches, but then realized they weren't keeping charges very well. The guy I gave them to for free sent me this lovely note and $50. I'm forwarding the $ to ALS research in honor of Rainer Grimm, consider contributing to ALS research if you can.

New on the blog: You Will Never Know Enough — Make peace (and progress) with incomplete knowledge kevlinhenney.medium.com/you-will-nev...

@matt.godbolt.org is this a compiler explorer competitor? www.youtube.com/watch?v=pJ-2...

A few folks have asked if there's a single list of the #AoCO2025 posts and there is: xania.org/AoCO2025-arc... It's in reverse order but they're all there!

Day 25 of #AoCO2025! 🎄 The final day! Thank you for joining this journey through compiler optimisations. From xor to vectorisation, it's been a wild ride. Happy holidays! 🎁 xania.org/202512/25-th... youtu.be/N1sRfYwzmso

On third glass of mulled wine. Final post of advent tomorrow might be a bit delayed :)

Secret Santa, @tomvii.bsky.social edition: youtu.be/4pG8_bWpmaE?... And....another cameo from yours truly :-)

Day 24 of #AoCO2025! A loop summing 0+1+2+...+n. GCC unrolls it. Clang does something jaw-dropping: the loop vanishes entirely, replaced by a direct calculation. How?! xania.org/202512/24-cu... youtu.be/V9dy34slaxA

If you weren't already sick of me: here's a recording of a talk I gave in November at Jane Street on Intel's Skylake Microarchitecture: youtu.be/BVVNtG5dgks?...

Day 23 of #AoCO2025! Switch → jump table? Sometimes. Other times: arithmetic, bitmasks, or something cleverer. Compilers have more tricks than you think. xania.org/202512/23-sw... youtu.be/aSljdPafBAw

In case you missed it Roojliek, my classic ASCII roguelike, is now available for the Sega #MasterSystem Download now from jimblimey.itch.io/roojliek

A huge thank you to everyone who has chosen to subscribe to my Acorn nonsense on YouTube, there are 2,250 of you now, for which I feel immensely honoured. Thanks for all the likes, comments and goodwill, all of which keeps me wanting to make more videos. Have a lovely Christmas!

Ep 512 - reinterpret_cast is Finally Fixed! youtu.be/JtFVyXQ00PQ

Day 22: String comparison against "ABCDEFG" should call memcmp, but Clang inlines it with some clever memory tricks. How does it compare 7 bytes so efficiently? xania.org/202512/22-me... youtu.be/kXmqwJoaapg #AoCO2025

Just edited the last of the #AoCO2025. It's been a blast but holy smoke is it a bunch of work! Now time to go remind my wife what I look like :-)

Day 21: Summing integers? Compiler vectorises beautifully—8 at a time! Switch to floats? It refuses, doing each add individually. Same code, totally different output. Why? 🤔 xania.org/202512/21-ve... youtu.be/lUTvi_96-D8 #AoCO2025

Americans - take that superfluous "s" that you add to Lego, and put it rightfully onto the end of Maths.

Day 20: Process 65,536 integers one at a time? Nah. The compiler vectorises it to handle 8 at once — same code, 8× faster! SIMD auto-vectorisation is compiler magic 🚀 xania.org/202512/20-si... youtu.be/d68x8TF7XJs #AoCO2025

Just surpassed 200k views on my channel this month! Astonishing stuff: yay!

Day 19: Recursive functions calling themselves endlessly — stack growth? Nope! The compiler turns recursion into loops. Tail call optimisation is magic ✨ xania.org/202512/19-ta... youtu.be/J1vtP0QDLLU #AoCO2025

My new gadget also works with Rust ☕🦀 @compiler-explorer.com

FYI, besides having the evolution of C++11->C++26 and an adventure game, my website now also has a fully cross-linked database of C++ Weekly episodes! cppevo.dev/episodes/ Want to see which episodes correlate to which parts of the standard and then jump into the adventure game engine to explore?

Day 18: Function with fast & slow paths. Inline = code bloat. Don't inline = slow fast path. Can't have both—or can you? The compiler finds a surprising way out of this dilemma. xania.org/202512/18-pa... youtu.be/STZb5K5sPDs #AoCO2025

Day 17: Inlining — the ultimate optimisation ✨ A function gets inlined, half vanishes. The assembly is cleaner than hand-written. How does copy-paste make code disappear? xania.org/202512/17-in... youtu.be/JFHfFTvMPp0 #AoCO2025

Day 16: Calling conventions matter! Pass 8 chars as separate args: stack spillage. Pack them in a struct: single register. Sometimes structs are MORE efficient than separate parameters! xania.org/202512/16-ca... youtu.be/Yaw8AMoP4sI #AoCO2025

Driving down my alley, the ice is so thick and so deeply tracked that it's like driving one of those cars in the Tomorrow Speedway at Disney World: you have the illusion of steering but you're only going where the track is.

so after being bedridden for 16months due to a hernia, I've finally got my surgery! now I'm bedridden for recovery, fun! I'm still about 2000$ away from paying all my storage bills, so if you've got a couple dollars, it'd help me get through this last stretch. Thanks so much! ko-fi.com/fooneturing

Day 15: Two nearly identical loops—one writes to memory every iteration, the other stays in registers. Same code, wildly different performance. The culprit? Aliasing! xania.org/202512/15-al... youtu.be/PPJtJzT2U04 #AoCO2025

Phew! I am edited up to next weekend which buys me time to not panic in the evenings this week. What a silly idea to release a daily video /and/ start a new job...

Day 14: Add ONE global counter to your loop and watch LICM vanish—strlen called every iteration! Why would incrementing an unrelated variable break the optimisation? 🤔 xania.org/202512/14-li... youtu.be/OwFNblEEAXo #AoCO2025

DaVinci Resolve crashing on a choice frame here :(

Ah windows

Deeply disappointed to hear that the BBC has pushed out one of the most brilliant presenters in all of science communication for speaking with integrity and honor in support of human rights and dignity.

Passed the halfway point of the #AoCO2025 (!!) where has the time gone?!

Day 13 of Advent of Compiler Optimisations! 🔄 Loop calling a function whose result never changes? One compiler hoists it out automatically. The other… doesn't. Even with hints! xania.org/202512/13-li... youtu.be/dIwaqJG0WDo #AoCO2025

This is indeed excellent advice.

Day 12 of Advent of Compiler Optimisations! A loop that checks the same thing every time. The compiler's solution? Make the code bigger to make it faster. Wait, what? xania.org/202512/12-lo... youtu.be/-VCrYshE7iQ #AoCO2025

I've built a text adventure game engine on top of the C++ Standard. Why? I have no idea. But it's a learning tool with quests and time travel and artifacts and NPC's and XP and ... well, you just have to check it out! cppevo.dev/adventure

Day 11: A clever bit-counting loop using the "clear bottom bit" trick. Change one compiler flag and... wait, what just happened to my loop?! Pattern recognition at its finest. xania.org/202512/11-po... youtu.be/Hu0vu1tpZnc #AoCO2025

Cripes, heading towards 20k humans who liked what I do enough to subscribe to my YT videos! 10 #AoCO2025 videos in, 15 to go... I've filmed most of them and edited up to 17, but it's a lengthy process (!) Hopefully I can keep ahead of the calendar :-)

Day 10: Fixed loop count? Compiler transforms code surprisingly. At 50 iterations it switches strategy. What's the cutoff and why? xania.org/202512/10-lo... youtu.be/HvF3tF2efEA #AoCO2025

Day 9: Why does the compiler keep an "expensive" multiply in the loop instead of using clever addition tricks? The slower operation enables something more valuable. What's the hidden benefit? xania.org/202512/09-in... youtu.be/vZk7Br6Vh1U #AoCO2025