A Fast 64-Bit Date Algorithm (30–40% faster by counting dates backwards)
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Re: A Fast 64-Bit Date Algorithm (30–40% faster by counting dates backwards)
#2A write-up of a new Gregorian date conversion algorithm.
It achieves a 30–40% speed improvement on x86-64 and ARM64 (Apple M4 Pro) by reversing the direction of the year count and reducing the operation count (4 multiplications instead of the usual 7+).
Paper-style explanation, benchmarks on multiple architectures, and full open-source C++ implementation.
Re: A Fast 64-Bit Date Algorithm (30–40% faster by counting dates backwards)
#3A write-up of a new Gregorian date conversion algorithm. It achieves a 30–40% speed improvement on x86-64 and ARM64 (Apple M4 Pro) by reversing the direction of the year count and reducing the operation count (4 multiplications instead of the usual 7+). Paper-style explanation, benchmarks on multiple architectures, and full open-source C++ implementation.
Very nice writeup!
> Years are calculated backwards
How did that insight come about?
Re: A Fast 64-Bit Date Algorithm (30–40% faster by counting dates backwards)
#4Nice to see the micro-optimising folks are still making progress on really foundational pieces of the programming stack
Re: A Fast 64-Bit Date Algorithm (30–40% faster by counting dates backwards)
#5> The algorithm provides accurate results over a period of ±1.89 Trillion years
i'm placing my bets that in a few thousand years we'll have changed calendar system entirely haha
but, really interesting to see the insane methods used to achieve this
Re: A Fast 64-Bit Date Algorithm (30–40% faster by counting dates backwards)
#6[deleted]
Re: A Fast 64-Bit Date Algorithm (30–40% faster by counting dates backwards)
#7I wrote my own date calculation functions a while ago. And during that, I had an aha moment to treat March 1 as the beginning of the year during internal calculations[0]. I thought it was a stroke of genius. It turns out this article says that’s the traditional way.
[0]: https://github.com/kccqzy/smartcal/blob/9cfddf7e85c2c65aa6de...
Re: A Fast 64-Bit Date Algorithm (30–40% faster by counting dates backwards)
#8Nice to see the micro-optimising folks are still making progress on really foundational pieces of the programming stack
Yes, some sharing Vibe coded slop.
Re: A Fast 64-Bit Date Algorithm (30–40% faster by counting dates backwards)
#9Nice to see that there are still some jewels left to be dug out from the algorithm land.
Re: A Fast 64-Bit Date Algorithm (30–40% faster by counting dates backwards)
#10> The algorithm provides accurate results over a period of ±1.89 Trillion years i'm placing my bets that in a few thousand years we'll have changed calendar system entirely haha but, really interesting to see the insane methods used to achieve this
Wouldn’t it be accurate for that as well? Unless we change to base 10 time units or something. Then we all have a lot of work to do.
But if it’s just about starting over from 0 being the AI apocalypse or something, I’m sure it’ll be more manageable, and the fix could hopefully be done on a cave wall using a flint spear tip.