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It Can Happen to You

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Re: It Can Happen to You

#31

Post by exporectomy »

jbluepolarbear wrote: post #4
rectang wrote: post #2

Pro tip: the classic recursive approach to implementing the Fibonacci sequence exhibits eye-wateringly poor performance.

Looped algorithms generally outperform recursive algorithms.

And don't cause stack overflows in normal operation. I've run into that before and now avoid recursion.

Re: It Can Happen to You

#32

Post by johnfn »

Loving the progression here. Tomorrow, someone’s going to reduce the boot times of macOS by 90% by the same principle. A week from now, someone will prove P=NP because all the problems we thought were NP were just running strlen() on the whole input.

Re: It Can Happen to You

#34

Post by epr »

decasia wrote: post #5

It would be nice if it were more common for standard library functions to include algorithmic complexity as part of the standard documentation. Absent that, of course we can potentially read the source code and find out, but I think for the most part we tend to operate based on an informed assumption about what we imagine the algorithmic complexity of a given operation would be. Inevitably, sometimes the assumption i…

Keeping track of algorithmic complexity would be nice as a language and/or static analysis feature. If you wanted to be exact or do it for a language with complex metaprogramming I assume it would be a nightmare to implement. Absent those complications and especially if you always reduced it to O(1), O(n), O(log(n)), etc it might not even be that difficult given the potential advantages.

Re: It Can Happen to You

#35

Post by scaramanga »

"it will open a 97 MB binary STL file in about 165 milliseconds flat, on a 2013 Macbook Pro. This is blinding fast."

This actually sounds incredibly slow, that's nearly 1/5th of an entire second. What can it possibly be doing? :)

In case anyone else was wondering, I followed the link and clicked the description and this is actually based on the time to the first frame being rendered - not just the time to load the file (which should be essentially infinitely fast). So it's actually more impressive than it sounds.

Re: It Can Happen to You

#37

Post by dmitryminkovsky »

dutchbrit wrote: post #36
kellyrose019 wrote: post #33

I'm available, just follow my link https://rebrand.ly/sexygirls007

Well, that’s the first time I’ve encountered real spam on HN...

Same! In all these years... I am examining it now and dare is say it is just basic spam. "It's better than Tinder!" A redirect but then just a very small, simple page with no JS that looks malicious. Strange community to target. :/

Re: It Can Happen to You

#38

Post by rudedogg »

tux3 wrote: post #15

The moral of the story, as far as I'm concerned: do NOT parse strings in C! Use a library, prefferably in a higher-level language. C string handling is a mess of viciously surprising APIs, juggling those particular footguns is almost certainly not your least bad option.

Funny, the ergonomics of the Swift string API are so bad that I've started learning a lower level language for parsing, etc.

Here's my favorite WTF: https://christiantietze.de/posts/2020/01/string-index-offset...

Re: It Can Happen to You

#39

Post by dfox »

tux3 wrote: post #15

The moral of the story, as far as I'm concerned: do NOT parse strings in C! Use a library, prefferably in a higher-level language. C string handling is a mess of viciously surprising APIs, juggling those particular footguns is almost certainly not your least bad option.

For me the moral of the story is do not use (whatever)scanf() for anything other than toy programs. In most cases implementing your own tokenizer (for both of these cases of reading numbers that involves str(c)spn() to get length of candidate token and then strtosomething()) is significantly easier than reasoning about what scanf() really does (even ignoring accidentally quadratic implementation details) and whether that can be adapted to your usecase.

Re: It Can Happen to You

#40

Post by mkeeter »

scaramanga wrote: post #35

"it will open a 97 MB binary STL file in about 165 milliseconds flat, on a 2013 Macbook Pro. This is blinding fast." This actually sounds incredibly slow, that's nearly 1/5th of an entire second. What can it possibly be doing? :) In case anyone else was wondering, I followed the link and clicked the description and this is actually based on the time to the first frame being rendered - not just the time to load the fi…

Touché – after all, disk-to-RAM is hundreds of MB/s, and faster if it's cached!

In practice, I'm racing mesh loading against "how long does the OS take to give you an OpenGL context", which is rarely below 160 ms (longer if it has to switch from integrated to discrete GPU).

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