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A polynomial autoencoder beats PCA on transformer embeddings

ivanpleshkov.dev

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Re: A polynomial autoencoder beats PCA on transformer embeddings

#11
post #4

My understanding after scanning the code examples is the technique expands the dimensionality of each data point with a set consisting of the quadratic coefficients of its existing dimensions. I thought it sounded like kernel PCA.

I think that kernel PCA is a strict superset of PCA. That would make it trivially true that it beats PCA.

Re: A polynomial autoencoder beats PCA on transformer embeddings

#12
This sound like projecting data into the linear space spanned by {x_i, x_i*x_j} where x_i are the features variables, and then applying standard regularization methods to remove noise and low value coefficients.

Anisotropy and the cone ideas may explain why PCA underperforms, but it does not uniquely justify this particular quadratic decoder. The geometric story is not doing explanatory work beyond “data is nonlinear,” and the real substance is simply that second-order reconstruction empirically helps.

Re: A polynomial autoencoder beats PCA on transformer embeddings

#14
post #5

I came here from a discussion about CS students who should not be bothered to set up email filters. How can they ever expect to be able to digest just the first paragraph in that article?

This kind of attitude isn’t long for this world. The time for this knowledge locked up in academia is over and in 15 years we’ll look back on this time as the dark ages as open code and models eclipses it.

None of this stuff is as difficult to understand as people claim it is once you work with it.

Re: A polynomial autoencoder beats PCA on transformer embeddings

#15
Geometric Algebra (GA) (Clifford Algebra) also has high potential to transform neural architectures. Models like the Geometric Algebra Transformer (GATr) and Versor (2026) demonstrate it can enhance or even make the Attention Mechanism obsolete.

By representing data as multivectors, translational and rotational symmetries are encoded natively which allows them to handle geometric hierarchies with massive efficiency gains (reports of up to 78x speedups and 200x parameter reductions) compared to standard Transformers.

> A novel sequence architecture is introduced, Versor, which uses Conformal Geometric Algebra (CGA) in place of traditional linear operations to achieve structural generalization and significant performance improvements on a variety of tasks, while offering improved interpretability and efficiency. By embedding states in the manifold and evolving them via geometric transformations (rotors), Versor natively represents -equivariant relationships without requiring explicit structural encoding. Versor is validated on chaotic N-body dynamics, topological reasoning, and standard multimodal benchmarks (CIFAR-10, WikiText-103), consistently outperforming Transformers, Graph Networks, and geometric baselines (GATr, EGNN).

https://arxiv.org/abs/2602.10195

Re: A polynomial autoencoder beats PCA on transformer embeddings

#16
post #9
post #2

Author here — questions and pushback both welcome.

Cool idea. But it only works when the data never changes. could you make a streaming/incremental version? One that updates the math cheaply when new data arrives, instead of recomputing everything, or does the math fundamentally prevent it?

[dead]

Re: A polynomial autoencoder beats PCA on transformer embeddings

#18
post #2

Author here — questions and pushback both welcome.

I think your per-axis std normalization is likely doing a big pile of the work —- it’s fairly well-known that “wrong” PCA, setting sigma=Id or just taking a square root, gives better embeddings than the un-normalized version. It would be worth showing a comparison to similarly-normalized PCA I think, if it’s not too hard?

Re: A polynomial autoencoder beats PCA on transformer embeddings

#19
post #2

Author here — questions and pushback both welcome.

Cool work! Something that worries me with PCA is that it's designed to retain variance, but variance might nor be the right metric for the semantics we want to retrieve. Ditto UMAP/tSNE that retains distances in lower dimensionality... If semantics are mostly encoded as directions on subsets of dimensions, PCA and friends would be too blunt of a tool... I wonder if a better approach would be linear probes or other decoders for a wide range of the concepts one wants to retrieve, and then optimize compression while keeping those retrievals as high as possible... i.e. tune the compressor to the usecase, like MP3 or MPEG do.

Re: A polynomial autoencoder beats PCA on transformer embeddings

#20
post #5

I came here from a discussion about CS students who should not be bothered to set up email filters. How can they ever expect to be able to digest just the first paragraph in that article?

By taking a class in machine learning. What kind of a CS student can't set up an email filter??
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