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#python#mojo#language#code#more#open#https#compiler#rust#cuda
Discussion (186 Comments)Read Original on HackerNews
Performance wise it's the first language in long time that isn't just an LLVM wrapper. LLVM is still involved, but they are using it differently than say, Rust or Zig.
Very excited for Mojo once it's open sourced later this year.
Hopefully they get Mojo to a good place for more general ML, but at the moment it still feels quite limited - they've actually deprecated some of the nice builtins they had for Tensors etc... For now I'll stick with JAX and check in periodically, fingers crossed.
Surely this is the sort of thing compiler / language design nerds dream about?
It doesn’t have to guarantee efficiency or provide cutting edge performance in any context … it should just exist!
My understanding is that we can make such a language … but it’s not caught the fancy of someone who could do it
That’s what compilers and high level languages are supposed to be for!
It's already (partly) existed called D language, by default it's garbage collected (GC), can also be program without it or hybrid. It's a modern, backward compatible with C and it's included in GCC.
The linear algebra system in D or Mir GLAS is standalone BLAS implementation written directly in D [1]. It's already proven faster than the other widely existing conventional BLAS like OpenBLAS back in 2016, about ten years ago!
This popular OpenBLAS include Fortran based LAPACK (yes you read it right Fortran) and it is being used by almost all data processing languages currently Matlab, Julia, Rust and also Mojo [2].
Interestingly there is a very early stage of standalone BLAS implementation written directly in Mojo namely mojoBLAS similar to Mir GLAS just started very recently [3].
>Surely this is the sort of thing compiler / language design nerds dream about?
You can say this again.
Especially on the GC side of the programming language since this SIMD / multi thread / multiprocessing / GPU can be abstracted away.
Actually someone recently proposed VGC or virtualized garbage collector for Python in C++ for heteregenous GC [4],[5]. However, the current evaluation excludes JIT compilation, AOT optimization, SIMD acceleration, and GPU offloading.
[1] OpenBLAS:
https://en.wikipedia.org/wiki/OpenBLAS
[2] Numeric age for D: Mir GLAS is faster than OpenBLAS and Eigen:
http://blog.mir.dlang.io/glas/benchmark/openblas/2016/09/23/...
[3] mojoBLAS:
https://github.com/shivasankarka/mojoBLAS
[4] Virtual Garbage Collector (VGC): A Zone-Based Garbage Collection Architecture for Python's Parallel Runtime:
https://arxiv.org/abs/2512.23768
[5] VGC-for-arxiv:
https://github.com/Abdullahlab-n/VGC-for-arxiv
All the flaws I can think of in Kotlin are due to the Java compatibility. They could've made it work here by being more explicit but the way it currently works seems doomed.
All the use of Kotlin in industry are due to Java compatibility. Else there would be ~0% marketshare of Kotlin.
> Supporting more of Python's dynamic features like classes, inheritance, and untyped variables to maximize compatibility with Python code.
What's more, note how it says "to maximize compatibility" not "to achieve full compatibility."
Yes the underlying platform they based their compatibility on, is the reason they got some design flaws, some more than other.
However that compatibility is the reason they won wide adoption in first place.
Unless it's open sourced, it's a moot point, as most Python devs wont come anyway.
> We're committed to open-sourcing all of Mojo, but the language is still very young and we believe a tight-knit group of engineers with a common vision moves faster than a community-driven effort. So we will continue to plan and prioritize the Mojo roadmap within Modular until more of its internal architecture is fleshed out.
I hope they stick to their original promise. And the 1.0 release would be a great time to deliver this.
Translated from corporatese it means "it will never happen".
Doesn't matter if it was closed, when the alternatives were much worse.
Someone else here is bringing up Julia. Which I think is a fine language but the compiler error messages and the library documentation are not what I would want in a language as far along as it is. I'm also worried about the correctness issues I've read about in a blog awhile back. Also I don't feel like I can make the kind of Python module I want with it (because of binary size and time to first x)
That being said I'm only hoping that Mojo can become an option. But I really like to use a REPL and I like the dynamicness of Python. So I might not ever get around to doing anything outside of maybe Numpy for performance.
For me it's the opposite - the only thing I like about Python is it's syntax. That's why I really like Nim - you get C speed, "comptime", metaprogramming, powerful type system, memory safety and code is often short and elegant.
Mojo seems interesting too, but so far they're mostly focused on ML stuff and not general programming. And I believe compiler is still not open-source?
I also think Mojo is more focused on being an industrial strength language. I was shocked to see the first iteration of Julia ahead of time compilation did not provide file I/O.
https://docs.modular.com/mojo/faq/#will-mojo-be-open-sourced
The messaging was changed because people got sold too hard on that, and kept trying Mojo with the expectation that it could compile existing Python code when it couldn't. What Modular did was change the messaging to reflect what Mojo is today, and provide a roadmap[1] of what they hope it'll turn into in the future. As it evolves, the messaging will evolve with it to continue reflecting current capabilities.
1. https://mojolang.org/docs/roadmap/
And it wasn't "equivalent python", whatever that means, they did loop unrolling and SIMD and stuff. That can't be done in pure python at all, so there literally is no equivalent python.
Chris Lattner talked more about the relationship between MLIR and Mojo than Python and Mojo.
The Mojo docs include two sections dedicated to these topics:
https://mojolang.org/docs/manual/values/
https://mojolang.org/docs/manual/lifecycle/
The metaprogramming story seems to take inspiration from Zig, but the way comptime, parameters and ownership blend in Mojo seems relatively novel to me (as a spectator/layman):
https://mojolang.org/docs/manual/metaprogramming/
I was sort of paying attention to all these ideas and concepts two-three years ago from the sidelines (partially with the idea to learn how Julia could potentially evolve) but it's far from my area of expertise, I might well be getting stuff wrong.
That and the not completely open source development model is what has always felt very vaporwary to me.
Python interop > Mojo natively interoperates with Python so you can eliminate performance bottlenecks in existing code without rewriting everything. You can start with one function, and scale up as needed to move performance-critical code into Mojo. Your Mojo code imports naturally into Python and packages together for distribution. Likewise, you can import libraries from the Python ecosystem into your Mojo code.
> Our long-term goal is to make Mojo a superset of Python (that is, to make Mojo compatible with existing Python programs). Python programmers should be able to use Mojo immediately, and be able to access the huge ecosystem of Python packages that are available today.
It's possible the language evolves to that in the longterm, but it's not the short term goal.
We published a Mojo roadmap on Mojolang.org that helps contextualize this: https://mojolang.org/docs/roadmap/
Note: I work at Modular
That was the original claim, but it was quietly removed from the website. (Did they fall for the common “Python is a simple language” misconception?).
Now they promise I can “write like Python”, but don’t even support fundamentals like classes (which are part of stage 3 of the roadmap, but they’re still working on stage 1).
Maybe Mojo will achieve all its goals, but so far has been over-promising and under-delivering - it’s starting to remind me of the V language.
For me this was a big disappointment, and I wonder how much this has backfired across developers.
Might not have the niceties purists like, but perhaps that's exactly it's a great language for that.
It's like executable pseudocode, and unlike other languages, all the ceremony is optional.
People flocked to it way before it became a "must" for ML and CS thanks to that ecosystem becoming dominant.
Event though it's not portable, it will likely have far greater usage than Mojo just by being heavely promoted by Nvidia, integrated in dev tools and working alongside existing CUDA code.
Tile IR was more likely a response to the threat of Triton rather than Mojo, at least from the pov of how easy is to write a decently performing LLM kernel.
Not to mention efforts like GraalPy and PyPy.
And all these efforts work today in Windows, which is quite relevant in companies where that is the assigned device to most employees, even if the servers run Linux distros.
I keep wondering if this isn't going to be another Swift for Tensorflow kind of outcome.
You always need to touch the hardware/platform APIs at some level, because even if the same code executes the same, the observed performance, or in the case of GPUs the numeric accuracy has visible side effects.
Of course, this won't be necessary in most cases if you're building on top of abstractions provided by Modular.
You don't get this choice using vendor-specific libraries; you're locked into this or that.
Python cuTile JIT compiler allows writing CUDA kernels in straight Python.
AMD and Intel are following up with similar approaches.
If Mojo will still arrive on time to gain wider adoption remains to be seen.
It is currently not straight Python and will never be.
All these "Performance friendly" python dialects (Tryton, Pythran, CuTile, Numba, Pycell, cuPy, ...) appears like Python but are nothing like Python as soon as you scratch the surface.
They are DSL with a python-looking syntax but made to be optimized, typed and inferred properly. And it feels like it when you use it: in each of them, there is many (most?) python features you simply can not use while you still suffer of inherent python issues.
Lets not lie to ourself: Python is inherently bad for efficiency and performance.
And that goes way beyond the GIL: dynamic typing, reference semantics, monkey patching, ultra-dynamic object model, CPython ABI, BigInt by default, runtime module system, ... are all technical choices that makes sense for a small scripting language but terribly sucks for HPC and efficiency.
The entire Numpy/scipy ecosystem itself is already just a hack around Python limitations for simple CPU bound tensor arithmetics. Mainly because builtin python performance sucks so much that a simple for loop would make Excel looks like a race horse.
Mojo is different.
Mojo tries to start from a clean sheet instead of hacking the existing crap.
And tries to provide a "Python like experience" but on top of a well designed language constructed over past language design experience (Python is >30y old)
And just for that, I wish them success.
Their whole original pitch was to be a superset of Python btw.
To my understanding, they offer a full python compatibility but guide the user to something else.
For instance, Mojo itself is statically typed.
Which is the whole point. Python has properties that make it bad for massive, fast number twiddling. However, it’s exceptionally nice for doing all the command line parsing and file loading and setup and other wrapping tasks required to run those pipelines.
Fortran’s fantastic at math stuff. I’d sure hate to have to write all the related non-math stuff in it.
And yes, Python’s slower than other languages. But in production, most Python code spends a huge chunk of its time waiting for other code to execute. It takes more CPU for Python to parse an HTTP request or load data files than an AOT language would take, but it’s as efficient sitting there twiddling its thumbs waiting for a DB query or numeric library to finish.
> most Python code spends a huge chunk of its time waiting for other code to execute.
Highly dependent on what you are doing. That hasn't been my experience most of the time.
While I believe that Chris Lattner is a great compiler designer, his language design record has been less stellar. Swift bidirectional type inference for instance feels like it was implemented because they had a compiler algorithm that they wanted to use, rather than a genuine need, and is just a completely avoidable problem. Trying to make a HPC language that is also Python compatible was doomed from the start. Hopefully the damage from going into this direction will remain limited.
As for Python not being the ideal, there we agree, but the solutions with proper performance already exist, Lisp, Scheme, Julia, Futhark,...
Heck maybe someone could dig out StarLisp.
I did not argue about CUDA being proper C++ :)
I honestly believe that the best days of C++ as an accelerator language are behind.
That is the main problem currently: We do miss a modern language for system programming that play well with accelerators. C++ is not (really) one of them (Hello aliasing).
I do not know if Mojo will succeed there, but I wish them good luck.
Can anyone of the AI enthusiasts here explain, why, or, what is meant by
> As a compiled, statically-typed language, it's also ideal for agentic programming.
> why, or, what is meant by More errors caught at compile time means an agent can quickly check their work statically without unit and other tests.
Thus this desparate "AI native" marketing is probably necessary to even be considered relevant in an "agentic" world. Whether it's enough, only time will tell.
Python+ruff+pycheck and TypeScript are compiled to bytecode instead of machine code. They’re not statically typed in the Rust sense. And yet, I’ve watched model crank out good, valid in both of those without needing to be either strictly “compiled” or “statically typed”. Turns out AI couldn’t care less about those properties as long as you have good tooling to quickly check the code and iterate.
yes, except it's more ... on the same lines, just to hammer the point home:
it's web 2, it's SaaS, it's the latest weekly, er, sorry, daily, hottest JS framework, its the latest rap / punk / hippie / dreadlock / crewcut / swami / grunge/ guru hairstyle, it's agile, it's functional programming, it's OOP, it's OOAD, it's UML, its the Unix philosophy, its Booch notation, it's CASE tools, ... going back even further, it's structured programming, it's high-level languages, it's assemblers, its veganism, it's the keto diet, it's the Atkins diet, it's the paleo diet, it's cholesterol is bad, no, it's good, etc etc etc.
So, agents tend to do better the more feedback they can get. Type checking is pretty good for catching a bunch of dumb mistakes automatically.
The point is more hints for the agent is more better most of the time.
Regarding compilation and static typing, it's extremely helpful to be able to detect issues at compile time when doing agentic programming. That way, you don't run into as many problems at runtime, which of course the agent has more difficulty addressing. Unit tests can help bridge the gap somewhat but not entirely.
What's not stated on their website is that Mojo is likely a bad choice for agentic programming simply because there isn't much Mojo training data yet.
But yea, to write mojo 1.0 code even after getting errors might take a new training round, so next or even next-next models.
Overall I think there is going to be a lot of "old" gpu compute hanging around, and now that writing kernels is a lot easier than it has been, we might as well try and see what algorithms we can get working there.
I originally picked up Mojo for the SIMD, not for the GPU kernels. The SIMD usability in Mojo is outstanding.
Paper on the tool I wrote: https://doi.org/10.1093/bioadv/vbaf292
If more than a few percent of execution time is spent in Python you are probably doing it wrong.
Personally I don't even understand why Cython is a thing, just write performance critical functions in other languages:
<https://pypi.org/project/rustimport/>
<https://pypi.org/project/import-zig/>
Note that you can even start threads in those languages and use function calls as pseudo-RPC. All without an overly complex build system.
Also tools like numba can beat them all at way less effort.
Imho, dropping into other languages should be the last resort in any project.
Every program that starts with 1% of Python writes more Python and gets to 20,40, 60 and than 99% of it.
From my experience, AI revolves a lot around building up function pipelines, computing their derivatives, and passing tons of data through them; which composability and higher order functions from functional programming make it a breeze to describe.
I also feel that other fields than AI are moving towards building up large functional pipelines to produce outputs, which would make mojo suitable for those fields as well. I’m building in the space of CAD for example and I’d love to use a “functional mojo” language.
I think that nowadays with vibe/agentic coding, high performance Python-like languages become ever more important. Directly using AI agents to code, say, C++, is painful as the verbose nature of the language often causes the context window to explode.
Microsoft is invested into using AI for C++ code review, for example.
I bet that’s true for a great many people. There are too many wonderful FOSS languages to bother with one you can’t fix or adapt or share.
One would want to see either a strong community build up around it, or really hard evidence for a long-term commitment to the language from Modular. And the latter will take a long time to be assured of I think.
Also, editing tools need to catch up before very wide adoption of a language with a lot of new syntax.
- The MLIR approach, which was also designed by Chris Lattner while at Google, has proven quite valuable to create Python JIT DSL
- The Python ecosystem now being taken seriously by the main GPU vendors, thanks to MLIR, as all their proprietary compilers are based out of LLVM
- Others remember Swift for Tensorflow
For example you need to use some Mojo Max library to have fast optimized LLM kernels, but at that point you can just stay with Python that has fast optimized LLM kernels, like flashinfer.
Meanwhile Julia is more mature for the same purposes, and since last year NVidia is having feature parity between Python and C++ tooling on CUDA.
Python cuTile JIT compiler allows writing CUDA kernels in straight Python.
AMD and Intel are following up with similar approaches.
So will Mojo still arrive on time to gain wider adoption?
Time will tell.
If Mojo succeeds, it could be the one language spanning across those levels, while simplifying heterogeneous hardware programming.
What’s that supposed to mean?
The “build”/run/deploy system was the other major issue. All the python versions, virtual env etc seemed like a mess. A compiled language is so much better(I.e Go, Rust etc) IMHO.
Since there is not much Mojo code in the wild so the LLMs were trained on it, I wonder how it will work in practice.
Probably the agents will make lots of mistakes and you will spend 10x the tokens compared to using a language the model are well versed in.
But then I read this:
> AI native
> Mojo is built from the ground up to deliver the best performance on the diverse hardware that powers modern AI systems. As a compiled, statically-typed language, it's also ideal for agentic programming.
Well, no thank you. I know the irony here but I want nothing to do with a language made for robots.
Go on, give it a shot. It stops being intimidating soon! And remember that the uv we all love was heavily influenced by Cargo.
I remember Rust very fondly in fact. And I had the same experience as you, learning Rust made me a better Javascript programmer. Lets see if a little neural network can be as fun.
That's a very big claim.
Now I will probably rewrite the model in rust if I want to do anything with it (mostly for the web assembly target as I want this thing to run in browsers) but I will for sure be using Julia for further experimentation. Lovely language.
Funny you should say that... there was recently a very interesting announcement for a Julia-to-WASM compiler and a full-stack signals-based web framework:
https://discourse.julialang.org/t/ann-experimental-wasmtarge...
Modular is giving you at least a public promise that they will open source Mojo it this year but some how here it is a problem.
Unbelievable.
For instance, you can write Python without using CUDA. CUDA's existence doesn't make Python less useful. But what do you do when you bump into a bug in Mojo? You have no ability to fix it yourself. At best, you can report it to the authors and hope they care enough about it to put in the work and release an update. If you run into a Python problem, you, or someone in your org, or a paid consultant, can fix it even if the Python core team doesn't care about it.
But somehow it is a problem when Modular gives a single promise to open-source their Mojo compiler?
> For instance, you can write Python without using CUDA. CUDA's existence doesn't make Python less useful. But what do you do when you bump into a bug in Mojo? You have no ability to fix it yourself.
You don't use AI training / inference with bare Python at all.
PyTorch (which almost all AI researchers use) primarily uses CUDA as the default and it is less useful without it (all other backends are slower). If there is a bug in anywhere from PyTorch to the silicon, you need to investigate if it is a PyTorch problem, C++ or Python issue or both, or a CUDA driver issue.
So a bug in one place (Mojo) vs a bug in 4 different places and one of them (CUDA) will never be open source. The latter is worse.
> At best, you can report it to the authors and hope they care enough about it to put in the work and release an update. If you run into a Python problem, you, or someone in your org, or a paid consultant, can fix it even if the Python core team doesn't care about it.
You are assuming Modular will never open source the Mojo compiler, when it is clear that Nvidia has been completely hostile to opening anything related to CUDA and its compiler.
[0] https://en.wikipedia.org/wiki/Nvidia_CUDA_Compiler