After 600 experiments, here's what I discovered about JEPA world models
148 points by halcdev 3 hours ago | 28 comments

robotresearcher 2 hours ago
There’s a repeated theme here that I don’t understand. For example:

> (3) That's where I decided to build a harder test, where each task takes its start from one demonstration and its goal from another

> (4) I also built an interactive demo where I could place the block anywhere and pick any goal. [but] The goals in the harder test are frames from expert demonstrations

Why lean so hard on the demonstration examples? Surely the actual task here is to move between any two arbitrary poses.

So if the demonstration set is statistically strange in any way, you keep banging into that. And even if you get great results, you still haven’t shown that it generalizes to the generic system. And the one thing you know 100% about a physical robot system is that you will never encounter exactly the same situation twice.

Is there actually a reason to pick eval examples from the demonstrations instead of independent samples from the underlying task?

I’m pretty sure that the T-shoving problem doesn’t have goal reachability issues. And if it did, test 4 could run into them since the start pose is arbitrary.

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nightpool 24 minutes ago
Agreed, I don't know much about JEPA but i wish this article had explained / motivated the memory graph more. "3. Fill gaps in memory with transformed memories" in particular seemed really really damning for the models—when you removed the examples from the demonstration that were near the goal state, the model completely broke. It seems like the only way you could make the model work again would be to manually flip and transform the memories it did have so there was something in the vicinity of the goal location.

That seems like a really massive failure of the model to generalize? This doesn't seem like a new technique, it seems like you've discovered a pretty big issue with the fundamental setup

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reasonabl_human 2 hours ago
Hands-on learning is an awesome thing - especially in the age of AI!

But maybe worth reframing away from “discovering” - hierarchical planning, sub-goals, action chunking etc. are well understood - this is more of a… transcript of your personal learning journey?

Which is still cool to see. But I read through expecting there to be some kind of novel results. We probably need to categorize these kinds of posts a bit better.

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wilkystyle 2 hours ago
Hm, I get your perspective, but completely disagree with your expectation. I'm not sure I would be entitled to expect a discovery that is novel with regard to current scientific knowledge unless I'm reading a paper. The fact that it is couched as "I discovered" and posted to a personal blog should be more than enough to convey that you might not find novel scientific discoveries within.
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halcdev 3 hours ago
Let me know if you have any questions!
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pj_mukh 20 minutes ago
Thanks for doing this!

Basic question: couldn't something like probabilistic roadmaps [1] trivially solve this? Or am I missing something about the limitations of PRM's?

And if so, is that the best test for JEPA?

[1]:https://en.wikipedia.org/wiki/Probabilistic_roadmap

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bsaul 2 hours ago
I knew close to nothing about JEPA before reading your post, but i was under the impression this was supposed to be a contender for LLM's limitations, a way to do things "properly".

However, based on this article, i have the feeling that on the contrary, JEPA is filling a super niche problem, and is pretty much only trying to improve robotic motions in space.

Which of the two ideas is it ? Can JEPA technics be applied to a much more wide range of problems ? (like LLM and transformers)

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LarsDu88 2 hours ago
JEPA can be applied to text as well in the sense you can use it to build text embedding models, freeze your JEPA text embedder, then train a decoder over the top of that.

OF course your decoder model could end up doing a lot of the heavy lifting if your decoder loss was based on text reconstruction methods (which almost all LLMs use for eval purposes)

For certain tasks, you do need pixel/token level reconstruction fidelity to do a lot of things. Like image generation or text generation.

For other tasks, having a coherent representation of the world that can be computed quickly and intuitively is more salient. I suspect the human mind works more like JEPA than like an autoregressive LLM. Human children train on far less data to achieve extreme fidelity on a lot of tasks generative reconstruction loss based AI/ML techniques struggle with.

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carlmr 2 hours ago
I wanted to know how you made these animations, they look gorgeous!
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orbis-tertius 2 hours ago
Seconding that, gorgeous animations
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halcdev 2 hours ago
javascript and webgl magic ;)
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Xenograph 2 hours ago
there's no webgl on the page though afaict?
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whiplash451 2 hours ago
MCTS also solves push-T problems without training: https://github.com/olivkoch/gumbel-mcts
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luisgvv 38 minutes ago
Whenever I read stuff like this, I wonder how could I get into this field?

Awesome read!

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freecodeio 2 hours ago
as someone with an oled monitor that background effect gave me a small heart attack
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taikon 2 hours ago
There's weird subtle moving rainbow color hues on this webpage on mobile
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packeted 2 hours ago
In a world where I'm increasingly being triggered by the fonts default Claude uses, I really liked the font used for the title here - it's Faculty Glyphic FYI.
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sashank_1509 2 hours ago
AI; DR

If you’re going to use AI to generate text, keep it short and concise and meaty. I don’t hate reading AI, but I can’t read large walls of text for presumably some useful nugget of information in it.

https://www.pangram.com/history/2dd2b019-221a-4bee-bb6a-6b7e...

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rvz 2 hours ago
We are doomed if most of the comments here are just talking about the website layout and not the contents of the article.

Anyway:

> The physics of pushing a block doesn't change if you shift, rotate or mirror the whole table. So when the graph has no states near a goal, it can take demonstration segments from elsewhere, transform them to fit the gap, and plan through those. With these transformed segments, success came back to 85%

This is an interesting technique to recover incomplete states or lost memories after demonstration. I'm guessing that the original LeWM does not have technique of transformative memories if I am correct?

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prohackernewsus 2 hours ago
Cool
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mequelkramer 2 hours ago
[flagged]
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kooi 42 minutes ago
I'm calling it: JEPA is what unlocks general robotics. In a autonomy stack, LLMs are only useful at the planning level and above.
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Ohentis 3 hours ago
Website is borderline unusable on my phone. I suspect because of the animations? Either way not a great state of affairs
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phoghed 2 hours ago
For anyone considering skipping because of this, it works flawlessly on my several year old iPhone.

There is a faint somewhat distracting background animation though I think…

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halcdev 2 hours ago
Thanks! Glad to know it works for most people. I reduced the bg animation intensity.
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bsboxe 2 hours ago
Works perfectly fine for me on iOS 27.3 (with the exception of some glitching that was solved by disabling adaptive dark mode)
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halcdev 2 hours ago
Sorry about that- will investigate. What OS/browser are you using?
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dofm 2 hours ago
Older intel macs initially have quite large blank areas of scroll while the figures later in the page render.

Much better after scrolling through and then reloading.

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Aboutplants 2 hours ago
Looks perfectly fine for me
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