DumPy: NumPy except it's OK if you're dum

124•RebelPotato•10h ago

Comments

the__alchemist•7h ago

Clear articulation of why Numpy syntax is provincial and difficult to learn. Perhaps the clearest part of it clicks when the author compares the triple-nested loop to the numpy-function approach. The former is IMO (And the author thinks so) much easier to understand, and more universal.

Gimpei•6h ago

I’ve known some people who didn’t want to learn the syntax of numpy and did it all in loops, and the code was not easy to read. It was harder to read. The fundamental issue is that operations on high dimensional arrays are very difficult to reason about. Numpy can probably be improved, but I don’t think loops are the answer.

okigan•6h ago

What’s a better syntax then?

tikhonj•6h ago

The real question—to which I have absolutely no answer—is not about syntax, it's about concepts: what is a better way to think about higher-dimensional arrays rather than loops and indices? I'm convinced that something better exists and, if it existed, encoding it in a sufficiently expressive (ie probably not-Python) language would give us the corresponding syntax, but trying to come up with a better syntax without a better conceptual model won't get us very far.

Then again, maybe even that is wrong! "Notation as a tool for thought" and all that. Maybe "dimension-munging" in APL really is the best way to do these things, once you really understand it.

bee_rider•4h ago

Numpy seems somewhat constrained here… it grew out of the matrix ecosystem, and matrices map naturally to two-dimensional arrays (sidenote: it’s super annoying that we have n-dimensional matrices and n-dimensional arrays, but the matrix dimension maps to the width of the array).

Anyway, the general problem of having an n-dimensional array and wanting to dynamically… I dunno, it is a little tricky. But, sometimes when I see the examples people pop up with, I wonder how much pressure could be relieved if we just had a nice way of expressing operations on block or partitioned matrices. Like the canonical annoying example of wanting to apply solve using a series of small-ish matrices on a series of vectors, that’s just a block diagonal matrix…

CamperBob2•6h ago

English. "Write me a Python function or program that does X, Y, and Z on U and V using W." That will be the inevitable outcome of current trends, where relatively-primitive AI tools are used to write slightly more sophisticated code than would otherwise be written, which in turn is used to create slightly less-primitive AI tools.

For example, I just cut-and-pasted the author's own cri de coeur into Claude: https://claude.ai/share/1d750315-bffa-434b-a7e8-fb4d739ac89a Presumably at least one of the vectorized versions it replied with will work, although none is identical to the author's version.

When this cycle ends, high-level programs and functions will be as incomprehensible to most mainstream developers as assembly is today. Today's specs are tomorrow's programs.

Not a bad thing, really. And overdue, as the article makes all too clear. But the transition will be a dizzying one, with plenty of collateral disruption along the way.

willseth•6h ago

why_not_both.gif

breppp•6h ago

I've read the article and it didn't seem to me the author is suggesting loops

dahart•6h ago

The point here is not that it’s loops per se, the point is that the indexing is explicit. It seems like a big win to me. The article’s ~10 non-trivial examples all make the code easier to read, and more importantly, to understand exactly what the code is doing. It is true that some operations are difficult to reason about, that’s where explicit indexing really helps. The article resonates with me because I do want to learn numpy syntax, I’ve written hundreds of programs with nympy, spent countless hours doing battle with it, and I feel like I’m no better off now than someone who’s brand new to it. The indexing is constantly confounding, nothing ever just works. Anytime you see “None” and “axis=“ inside an operation, it’s a tell: bound to be difficult to comprehend. I’m always having to guess how to use some combination of reshape, dstack, hstack, transpose, and five other shape changers I’m forgetting, just to get something to work and it’s difficult to read and understand later. It feels like there is no debugging, only rewriting. I keep reading the manual for einsum over again and I’ve used it, but I can’t explain how, why, or when to use it, it seems like this thing you have to resort to because no other indexing seems to work. The ability to do straightforward explicit non-clever indexing as if you were writing loops seems like a pretty big step forward.

collingreen•4h ago

I involuntarily whispered "reshape" to myself near the top of your comment. Numpy is a very different way for me to think and I have similar feelings to what you're describing.

okigan•6h ago

Fantastic article.

I don’t use numpy often enough - but this explains the many WTF moments why it’s so annoying to get numpy pieces to work together.

crescit_eundo•6h ago

Dupe. Posted a number of times the past day and a half:

https://news.ycombinator.com/item?id=44072775

https://news.ycombinator.com/item?id=44063553

https://news.ycombinator.com/item?id=44078019

https://news.ycombinator.com/item?id=44063490

homarp•5h ago

but only https://news.ycombinator.com/item?id=44063490 has 'some' comments. so this current discussion is better

gus_massa•5h ago

There is an "older" discussion with a different title: https://news.ycombinator.com/item?id=43996431 (488 points | 9 days ago | 212 comments)

palmtree3000•5h ago

That's a different post.

gus_massa•4h ago

You are right. It's a 1 letter difference in the URL and I missed it. Sorry for the noise.

kevmo314•6h ago

I’m not convinced by the loops proposal. TensorFlow had this kind of lazy evaluation (except I guess TF was the worst of both worlds) and it makes debugging very difficult to the point that I believe it’s the main reason PyTorch won out. Such systems are great if they work perfectly but they never do.

NumPy definitely has some rough edges, I sympathize with the frustrations for sure.

mpascale00•6h ago

In the way that `ggplot2` tries to abstract those common "high dimensional" graphing components into an intuitive grammar, such that you may in many places be able to guess the sequence of commands correctly, I would love to see an equivalent ergonomic notation. This gets part way there by acknowledging the problem.

Mathematical operations aren't obliged to respect the Zen of Python, but I like the thought that we could make it so that most have an obvious expression.

shiandow•6h ago

That is amazing. My main doubt would be how future proof this is. Does it wrap numpy? Or something equivalent? Does it require continuous development to keep up?

Also I both understand the need for declaring the matrices up front and think it's a bit of a shame that it is not seamless.

Here are some (ill-advised?) alternatives:

    X, Y, Z = dp.Slots()
    
    with dp.Slot() as X:
        ...
    
    import dp.Slot as new
    X = new['i','j'] = ...

    X = dp['i','j'] = ...

darepublic•5h ago

Need transpilation rather than relying on this library being present. I like the idea alot though

dynm•5h ago

(author here) This wraps JAX and JAX's version of NumPy. It would surely require some development to keep up, although it's quite short and simple (only 700 lines), so I don't think it would be a big burden. That said, I should be clear that my goal here is just to show that this is possible/easy, and possibly inspire existing array packages to consider adding this kind of syntax.

I like your alternatives! I agree that having to write

  X = dp.Slot()

before assigning to X is unfortunate. I settled on the current syntax mostly just because I thought it was the choice that made it most "obvious" what was happening under the hood. If you really want to, you could use the walrus operator and write

  (X := dp.Slot())['i','j'] = ...

but this cure seems worse than the disease...

Actually, doing something like

  X = new['i','j'] = ...

could simplify the implementation. Currently, a Slot has to act both like an Array and a Slot, which is slightly awkward. If new is a special object, it could just return an Array, which would be a bit nicer.

turtletontine•5h ago

Pretty sure Numpy’s einsum[1] function allows all of this reasoning in vanilla numpy (albeit with a different interface that I assume this author likes less than theirs). Quite sure that first example of how annoying numpy can be could be written much simpler with einsum.

[1]: https://numpy.org/doc/stable/reference/generated/numpy.einsu...

jampekka•5h ago

Sure, but einsum needs a syntax and concepts of its own, and more importantly does not work if you need to do something else than a limited set of matrix operations.

sottol•5h ago

The author posted a previous article about why they don't like numpy and his problems with einsum:

https://dynomight.net/numpy/

yorwba•4h ago

How do you invert a matrix with einsum?

BeetleB•3h ago

Why do you need to invert a matrix?

yorwba•2h ago

It's what the "first example of how annoying numpy can be" does, using either np.linalg.solve in a loop or a cursed multidimensional index rearrangement.

ltbarcly3•5h ago

The kind of person with the background to need these operations, and who is working on the kinds of problems where this stuff comes up, is more than capable of learning numpys syntax. Its not that bad.

Avoiding the special purpose tools designed by and used by the people who work on these problems every day is the instinct of someone who has just started needing them and wants to solve new kinds of problems with the tools they already know. But the people with experience don't do it that way (for a reason), you need to learn what the current best solution is before you can transcend it.

Guys, every few months some well meaning person posts their great new library here that "fixes" something to remove all that pesky complexity. Invariably its made by some beginner with whatever it is who doesn't understand why the complexity exists, and we never hear of them or the library again. This is absolutely one of those times.

lblume•3h ago

I agree that this may sometimes be the case, but in this case the author does seem to have very strong points in favor of the proposal. I also think that the accusation of dynomight not understanding NumPy enough is unjustified based on the points given.

jampekka•5h ago

Lots to like here but I'm not so sure about this:

> In DumPy, every time you index an array or assign to a dp.Slot, it checks that all indices have been included.

Not having to specify all indices makes for more generic implementations. Sure, the broadcasting rules could be simpler and more consistent, but in the meantime (implicit) broadcasting is what makes NumPy so powerful and flexible.

Also I think straight up vmap would be cleaner IF Python did not intentionally make lambdas/FP so restricted and cumbersome apparently due to some emotional reasons.

cyanydeez•3h ago

Implicir means write once easy, debug, extend, read hard.

jampekka•2h ago

It also means that you don't have to reimplement the same things all over again when your dimensions change.

thanhhaimai•3h ago

For solo works, the terseness might work, but usually only in short term. Code I wrote 6 months ago looks like someone else's code. For team work, I'd prefer to be explicit if possible. It saves both my teammates' time and my time (when I eventually forget my own code 6 months from now).

jampekka•2h ago

It's not (only) about terseness. It's about generality.

netbioserror•5h ago

I think this sort of DSL construction is a perfect fit for languages with macros: Lisp, Nim, etc. I spend a lot of time on both so I might explore the possibilities. What should a higher-dimensional array indexing, looping, and broadcasting syntax even look like, if until now it's just been cludges? Is it just APL but with actual words?

mlochbaum•3h ago

Author of BQN here, I agree with how section "What about APL?" describes the APL family as not fundamentally better (although details like indexing are often less messy). I outlined a system with lexically-scoped named axes at https://gist.github.com/mlochbaum/401e379ff09d422e2761e16fed... . The linear algebra example would end up something like this:

    solve(X[i,_], Y[j,_], A[i,j,_,_]) = over i, j/+: Y * linalg_solve(A, X)

bbminner•4h ago

Always wanted to experiment with a syntax like this myself, thanks to author! I completely agree with you reasoning re complexity of mental model for indexing vs broadcasting. Moreover, it appears to me that such a representation should allow for finding more optimal low level impls (something like deeper "out of order" op fusing, idk)? I've seen a paper from either nvidia or meta around five years ago doing exactly that - translating an index-based meta-language built on top of python into cuda kernels (usually several variants and picking the best), can't find the reference unfortunately.

bee_rider•4h ago

It seems like a neat idea. If it can just be layered on top of Jax pretty easily… I dunno, seems so simple it might actually get traction?

I wish I could peek at the alternative universe where Numpy just didn’t include broadcasting. Broadcasting is a sort of ridiculous idea. Trying to multiply a NxM matrix by a 1x1 matrix… should return an error, not perform some other operation totally unrelated to matrix multiplication!

jampekka•1h ago

Broadcasting is an excellent idea. Implementations do have warts, but e.g. pytorch would be really painful without it.

Broadcasting is a sort of generalization of the idea of scalar-matrix product. You could make that less "ridiculous" by requiring a Hadamard product with a constant value matrix instead.

duchenne•3h ago

Looks awesome. Can we get the same thing for pytorch?

joshjob42•2h ago

I think I'll just use Julia, since it has great libraries for doing matrix operations and mapping loops etc onto GPUs and handling indices etc. And if you need some Python library it's easily available using the fantastic PyCall library.

This is a big improvement over numpy, but I don't see much of a compelling reason to go back to Python.

jampekka•2h ago

> I don't see much of a compelling reason to go back to Python.

Being able to use sane programming workflows is quite a compelling reason.

3eb7988a1663•2h ago

Minor style complaint, but the code font is really light.

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DumPy: NumPy except it's OK if you're dum

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