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5 hours ago
Previously, in JF's "Can we acknowledge that every real computer works this way?" series: "Signed Integers are Two’s Complement" <https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p09...>
5 hours ago
Previously, in JF's "Can we acknowledge that every real computer works this way?" series: "Signed Integers are Two’s Complement" <https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p09...>
Maybe specifying that floats are always IEEE floats should be next? Though that would obsolete this Linux kernel classic so maybe not.
https://github.com/torvalds/linux/blob/master/include/math-e...
I'm literally giving a talk next week who's first slide is essentially "Why IEEE 754 is not a sufficient description of floating-point semantics" and I'm sitting here trying to figure out what needs to be thrown out of the talk to make it fit the time slot.
One of the most surprising things about floating-point is that very little is actually IEEE 754; most things are merely IEEE 754-ish, and there's a long tail of fiddly things that are different that make it only -ish.
The IEEE 754 standard has been updated several times, often by relaxing previous mandates in order to make various hardware implementations become compliant retroactively (eg, adding Intel's 80-bit floats as a standard floating point size).
It'll be interesting if the "-ish" bits are still "-ish" with the current standard.
I'm interested by your future talk, do you plan to publish a video or a transcript?
> there's a long tail of fiddly things that are different that make it only -ish.
Perhaps a way to fill some time would be gradually revealing parts of a convoluted Venn diagram or mind-map of the fiddling things. (That is, assuming there's any sane categorization.)
Hi! I'm JF. I half-jokingly threatened to do IEEE float in 2018 https://youtu.be/JhUxIVf1qok?si=QxZN_fIU2Th8vhxv&t=3250
I wouldn't want to lose the Linux humor tho!
I was curious about float16, and TIL that the 2008 revision of the standard includes it as an interchange format:
https://en.wikipedia.org/wiki/IEEE_754-2008_revision
That line is actually from a famous Dilbert cartoon.
I found this snapshot of it, though it's not on the real Dilbert site: https://www.reddit.com/r/linux/comments/73in9/computer_holy_...
This is the epitome, the climax, the crux, the ultimate, the holy grail, the crème de la crème of nerd sniping.
fuckin bravo
Whether double floats can silently have 80 bit accumulators is a controversial thing. Numerical analysis people like it. Computer science types seem not to because it's unpredictable. I lean towards, "we should have it, but it should be explicit", but this is not the most considered opinion. I think there's a legitimate reason why Intel included it in x87, and why DSPs include it.
Numerical analysis people do not like it. Having _explicitly controlled_ wider accumulation available is great. Having compilers deciding to do it for you or not in unpredictable ways is anathema.
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Love it