| ▲ | A decades-old bug in Knuth's long division (TAOCP Vol II, Algorithm 4.3.1D)(kolja.rs) |
| 72 points by nk_kolja 6 days ago | 15 comments |
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| ▲ | nk_kolja 6 days ago | parent | next [-] |
| I found a bug in Algorithm D, the long division algorithm in Knuth's "The Art of Computer Programming". It was discussed on HN a couple of times https://news.ycombinator.com/item?id=26562819 as well as on other websites.
I sent a letter to Knuth and received a check and an annotated reply. The updated Theorem B, which was unchanged since 1969 is now dated 2026. While searching for vulnerable implementations I also found a "bug" in llvm, so I expanded a bit on that too. |
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| ▲ | jason_s a day ago | parent | next [-] | | Congratulations! Wow, you got a legendary $2.56 check.... | | |
| ▲ | WillAdams 3 hours ago | parent | next [-] | | Unfortunately, one no longer gets physical checks, instead, one gets an account in The Bank of the Island of San Seriffe: https://www-cs-faculty.stanford.edu/~knuth/boss.html (unfortunately, I have yet to find another typo since getting my $2.88 for _Digital Typography_) | | |
| ▲ | bluGill 3 minutes ago | parent | next [-] | | Close enough. If I ever got such a check it would be professionally framed and hung on my wall. As would most people reading this. | |
| ▲ | malisper 2 hours ago | parent | prev [-] | | You still get a physical piece of paper that looks like a check; it's just not a valid check. | | |
| ▲ | nk_kolja 2 hours ago | parent [-] | | It can still be cashed in, though not in any bank, you need to contact Knuth beforehand. For me it will stay framed on the wall. |
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| ▲ | warmwaffles 3 hours ago | parent | prev [-] | | Hopefully framed it and put it on the wall. |
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| ▲ | AndruLuvisi 38 minutes ago | parent | prev [-] | | Wow, congratulations on finding this most epic bug! |
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| ▲ | globular-toast an hour ago | parent | prev | next [-] |
| > "I'm especially glad to have this correction, because I think the readers of TAOCP Vol 2 look at Algorithm 4.3.1 D more than any other algorithm!" If you look at the fore edge of my copy of vol 2 will see a noticeably grubby line. Open the book at that page and you do indeed arrive at Algorithm D! I've implemented multiple-precision arithmetic at least a couple of times. I'm tempted to dig up an old project I haven't touched for over a decade and make the correction... |
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| ▲ | ginko 3 hours ago | parent | prev [-] |
| The typesetting of this looks very broken on firefox with extreme gaps between lines of text. Seems to render fine on chromium. |
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| ▲ | Retr0id 2 hours ago | parent | next [-] | | It renders fine for me, but I've also had the "extreme gaps between lines" thing happen before on Firefox, and in my case it was caused by a bad font fallback - I forget the precise details but I think it had something to do with having Arabic fonts installed, which were erroneously taking preference for certain non-arabic glyphs. (Check the Fonts tab in dev tools) | |
| ▲ | voakbasda an hour ago | parent | prev | next [-] | | I believe this is a missing font issue, whereupon Firefox chooses very poor substitutes. I ran into this recently on one of my machines and solved it by installing the Microsoft fonts package (or possibly another one… I can’t remember now exactly which one did the trick). | | | |
| ▲ | nk_kolja 2 hours ago | parent | prev | next [-] | | Thank you for letting me now, but I cannot replicate the issue on Firefox.
There are some issues with math and the animations not breaking on mobile, which I am working on repairing. (fixed) EDIT: I have added a different fallback font so it should work on your Firefox now. | |
| ▲ | metalliqaz 2 hours ago | parent | prev [-] | | I use firefox and it renders approximately the same as Chrome for me. Assuming OP didn't patch something, you may have a misbehaving extension. |
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