ultratree

ultratree-results

This shows the results of the ultrametric tree-based, explainable, solar-powered language model

These charts update each day.

Interactive Next-Word Tree

This animation uses a tiny, inspectable decision tree to predict a next word from a sentence context. The default sentence comes from ../papers/ultratrees/ultratrees.tex.

Ready.

Rule semantics are illustrative and intentionally human-readable (not the production model).

Predicted next word: ?
Leaf candidates: -

Key Charts

Levels of carefulness

Training up an ultrametric tree by finding the optimal split at each step is computationally prohibitive. We can only subsample. Each order of magnitude increase in carefulness is roughly three orders of magnitude more compute time required. "Sense Annotated 1" is the alias of the first training of Careful1000, which seems like a reasonable compromise. It requires about 100 times as many nodes to achieve the same result as Careful10000, but it can train 1000 times faster.

Careful100 and Careful10 are much, much faster to train, but there's a threshold somewhere between Careful100 and Careful1000 where there are too many bad choices. It's open question what that threshold is, and why a threshold even exists.

Carefulness Levels

Does sense annotation work?

The key question that this work set out to answer was whether sense annotation, and indeed, the whole idea of synergistic semantic and statistical models were worth exploring.

The "Unannotated Model 1" can be seen as being a baseline statistical model. It's equivalent to a one-hot encoded decision tree. The sense annotated model's learning generalises where the unannotated model is overfitting very early.

Sense annotated vs Unannotated

Reproducibility and variance in models

Broadly speaking, re-training on the same data yields similar results. Loss on the hold-out training data goes down, roughly linearly with the logarithm of the number of nodes in the model. Note that these are only sorted by time (the model that was trained first). It's just co-incidence that model 1 is the best and model 5 the worst.

Even the worst model is doing much better than the unannotated model. The probability of this happening by chance is 1/32, which is equivalent to a p-value of 0.03.

Reproducibility of model training

Ensembling

Ensembling works. The ensemble of 5 "Careful 1000" models gets results that don't look all that different to an extrapolation of the best of them.

Total Loss vs Model Size for Sense Annotated Models Including Ensembling

Baseline Comparison

Comparison with a neural baseline shows that the best-trained ultrametric trees need a few orders of magnitude more nodes than a neural network needs trainable parameters. But different ultrametric training regimes have several orders of magnitude difference within them, so it's not hard to believe that a better training regime might close this gap.

Weirder is that here sense annotation makes barely any difference to the neural network models.

Neural Network Results

How many UltraTree parameters match a neural network?

This chart answers: for a given neural parameter budget, how many UltraTree nodes are needed to match the best neural total-loss result. Solid points are directly observed in evaluation data; dotted points are extrapolated because neural loss is better than the best observed UltraTree loss.

UltraTree Parameters Needed to Match Neural Loss

Training compute time vs parameters

This compares estimated training compute time against parameter count for both systems. For UltraTree, time comes from node-creation timestamps in Postgres (ultratree.nodes.when_created) with a 24-hour active-gap cutoff. For neural models, time is inferred from checkpoint file modification deltas in ultratree-neural-baseline.

Training Compute Time vs Parameter Count

Noun loss

Instead of looking at the total loss over all parts of speech, we would expect that nouns would get the most benefit from having sense annotation into a hierarchy.

But the data shows the exact opposite: as we train, we are increasing the loss on nouns, which means that the loss on all other parts of speech much be dropping even more rapidly.

Noun Loss vs Model Size

We do see that the ultratree models soundly outperform neural network models on nouns though. Neural networks are behaving as one would expect: larger models have more generalised learning.

Noun Loss vs Neural Networks

Theory: the ultrametric models mostly predict nouns, because nouns are the most common part of speech in the corpus, and they can group parts of speech together into an aggregate. The neural network mostly predicts punctuation, since it has no way of aggregating parts of speech together without internalising rules of grammar. The .'' character is the most common word'' in the corpus, so all else being equal, it will get predicted more often.

Context usage

We can see which contexts get used for node splitting. (This is not the same as asking which nodes get used the most often in inference.)

Histogram of context usage

Everything Else

Total Loss

Total Loss vs Model Size

Total Loss vs Model Size for the Careful 10000 model

Noun Loss

Noun Loss vs Model Size for Sense Annotated Models Including Ensembling

Noun Loss vs Model Size for the Careful 10000 model

Time Views

Total Loss vs Time

Noun Loss vs Time

Model Node Count vs Time

Model Complexity

Average Depth vs Time

Average In-Region Hits vs Time

Context Usage

Sense Annotated

Unannotated

How to reproduce these results (Postgres-first)

These site outputs are now generated from PostgreSQL data and do not require SQLite in the build/deploy flow.

Assumptions:

1. Load environment

cd ~/ultratree
set -a
source config/ultratree.env
set +a

2. Verify data exists

psql "$ULTRATREE_DATABASE_URL" -Atc "
  select model_type, count(*) from ultratree.evaluation_runs group by model_type order by model_type;
  select count(*) from ultratree.inferences;
"

3. Recalculate inference losses in Postgres

This is idempotent and does not retrain models.

python3 scripts/recalculate_inference_losses_postgres.py --dry-run
python3 scripts/recalculate_inference_losses_postgres.py

4. Build site from Postgres

./scripts/build_site_from_postgres.sh

This writes static output into site/dist/.

5. Deploy

./scripts/deploy_site.sh --src site/dist --dry-run
./scripts/deploy_site.sh --src site/dist

6. Verify site

curl -I https://ultratree.symmachus.org
curl -I "https://ultratree.symmachus.org/total_loss_vs_model_size.png?bust=$(date +%s)"