nightcracker

Yes, I am aware it has been 'superseded' but in my experience for lossless compression it's still usually better.

    QOI_DIFF24 {
        u8 tag  :  4;   // b1110
        u8 dr   :  5;   // 5-bit   red channel difference: -15..16
        u8 dg   :  5;   // 5-bit green channel difference: -15..16
        u8 db   :  5;   // 5-bit  blue channel difference: -15..16
        u8 da   :  5;   // 5-bit alpha channel difference: -15..16
    }

It bothers me more than it should that the 5-bit signed differences aren't -16..15 matching two's complement but -15..16 instead.

nightcracker

há 5 anosdiscuss

You could still stream the pixels, you'd just have to stream them in Z order. This may seem pedantic, but this applies to any mismatch between the order in which you store pixels and the order in which the format stores pixels.

E.g. some file formats may be row-major, others column-major, some block-based (like JPEG) or a fancy interleaving scheme (like Adam7). Some might store the channels interleaved, others separate the channels. If any of these choices doesn't match the desired output format, it breaks streaming.

nightcracker

há 5 anosdiscuss

Copying the question text verbatim certainly is copyright infringement (and I would guess unlikely to be fair use, but I'm not a lawyer). If you give the problem in your own words, it won't be, just like your solution isn't.

nightcracker

há 5 anosdiscuss

I don't know, only have some theories.

1. The name isn't particularly catchy or descriptive. It is the correct name for the data structure, but not too many people know the data structure.

2. People don't even know what they're missing. It's not a very Google-able problem to begin with. Slotmap provides an interesting solution to (circular) ownership and safe allocator / weak pointer design problems, but people don't recognize that they're having them or that slotmap could help.

As an example of this, the doubly linked list example (https://github.com/orlp/slotmap/blob/master/examples/doubly_...) can safely remove nodes from the linked list given their handle, in O(1), even from the middle, completely safely and correctly, even in the presence of double deletions or ABA memory re-use. You can't replicate this with just pointers, without introducing heavy refcounting solutions.

nightcracker

há 5 anosdiscuss

SlotMap literally cannot, because it must keep track of versions of the used slots, and the slots include the memory space for the data.

DenseSlotMap sort of can. It still can't reclaim the memory used by empty slots for the same reason (at a cost of 8 bytes per slot), but can reclaim the memory used by the actual elements stored.

So if you store 1 million items at one point in a DenseSlotMap, and then clear them all and then shrink to fit (which is actually missing from the API, but I'll fix that soon) you will waste 7.6 megabytes on the empty slots but nothing on the actual data that used to be stored.

nightcracker

há 5 anosdiscuss

There is no fragmentation whatsoever in the traditional sense (unusable gaps left due to size mismatches), because a slotmap only stores a single type of value. Thus every slot is interchangeable and memory can always be reused.

For iteration however, there can be holes that need to be ignored, if the current number of elements in the slotmap is significantly lower than the the maximum capacity. If iteration needs to be very fast (for e.g. game engines) I do have a solution for that, which is the DenseSlotMap. It uses one extra layer of indirection for random access, but stores the actual data values contiguously in a vector, thus iteration is always fast.

nightcracker

há 5 anosdiscuss

> It's not hard being faster than zip if you are not compressing/uncompressing

Actually, since CPUs are so fast and disk IO is so slow, it is essentially impossible to beat a properly tuned program that reads data from disk and decompresses it on the fly using one that doesn't use compression at all.

nightcracker

há 5 anosdiscuss

If a significant amount of your new customers find your physical shop through Google maps, what can you do? If someone wants to find a hardware store near them, good chance they'll just write "hardware store" on Google maps. The entry point of people's search is Google - you've already lost the game before it ever started.

nightcracker

há 5 anosdiscuss

I did miss that, oops. That said, it's again unclear if that curve is pre- or post- biased sampling. If it is on the original data it is quite good, but with a heavy biased sample fairly meaningless.

nightcracker

há 5 anosdiscuss

Very sloppy statistics. A lot of explanatory analysis on the model is done but the model is hardly justified in being predictive in the first place.

The paper (https://journals.plos.org/plosone/article?id=10.1371/journal...) [does not mention the sensitivity or specificity of the model at all, only mentions a '91% accuracy' number]* on a biased dataset (where the number of suicidal cases is oversampled and non-suicidal cases are undersampled), without even mentioning exactly how much they over/undersampled.

* I missed the ROC curve on page 7. However it's not clear if this ROC curve was computed on the under/oversampled dataset or the original.

nightcracker

há 5 anosdiscuss

No, it is a Pokémon reference to the very similarly named Excadrill.

nightcracker

há 5 anosdiscuss

Softball is a bigger ball, yes. But it's not lower velocity, at least if you consider the relevant metric: time from pitcher to plate. Because softball also pitches a lot closer to the plate.

nightcracker

há 5 anosdiscuss

See my other comment, it would also immediately be constructive: https://news.ycombinator.com/item?id=29022963

nightcracker

há 5 anosdiscuss

From what I have read (I don't do 3D modeling myself) Blender has overhauled its UI significantly over the past couple of years to great praise of a lot of people.

nightcracker

há 5 anosdiscuss

I would guess that India is too large to meaningfully include in such a statistic. On average in the country English literacy could be quite poor while in the relevant tech hubs it is quite good. But that's just a hypothesis.

nightcracker

há 5 anosdiscuss

> I can zoom in and see lots of different colors

If you zoom in further, you'd soon realize your screen is nothing but pure red, green and blue subpixels at varying intensities.

nightcracker

há 5 anosdiscuss

PNG is lossless, so it really does.

nightcracker

há 5 anosdiscuss

Here in the Netherlands it's the exact opposite. We have infinite water, just not a lot of space.

nightcracker

há 5 anosdiscuss

> and proving that a very simple physical machine can perform any computation (Turing completeness)

Not proving, conjecturing. It's not proven until this day: https://en.wikipedia.org/wiki/Church%E2%80%93Turing_thesis

nightcracker

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Extremely fast crypto signatures and Diffie-Hellman key exchange

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