The 17 building blocks of machine learning · 7 families · usage estimates 2026 · 1 open slot

Machine Learning Primitives

The short list of computational primitives that nearly all frontier-lab work is assembled from: what each is, the parameters it accepts, when to reach for it, where it fails, how heavily it is used, and what it pairs with. Every sheet closes with a reading of the primitive through a plant, so the open slot at the end, the one the Boquila exercise was trying to fill, has a shape.

How to read a sheet. Parameters list the knobs practitioners actually turn, with typical ranges. Pairing chips link to the primitives it combines with in practice. The plant label marks where a plant already runs something like it, or where plants have no equivalent at all, which is just as informative.

Seven families, one gap

Grouped by the question each family answers. Most real systems take one primitive from each of the first four rows and bolt them together; the substrate underneath almost everything is gradient descent.

How much each is used

Estimated share of frontier-lab production systems (the large language, multimodal and reasoning models shipped in 2025–26) whose pipeline depends on each primitive. These are my estimates from public technical reports, not measured figures; treat the ordering as reliable and the digits as rough.

Share of frontier production systems, 0–100, estimated. Hover a bar for the note.

Where the primitives sit in one frontier system

The mechanism, not the inventory: a corpus goes in on the left, an answer comes out on the right, and each primitive is placed at the stage where it actually does work. Solid arrows are the main path; dashed arrows are the tuning and search loops that run beside it.

STAGE 1 · PRETRAINING STAGE 2 · POST-TRAINING STAGE 3 · INFERENCE Corpus text · image · code 06 Attention the model body 15 Self-supervised objective next-token · contrastive 01 Gradient descent the substrate · every stage 04 Convolution vision encoder 05 Recurrence hybrid layers 09 Reinforcement RLHF · verifiable reward 08 Bellman backup inside the value estimate 16 Retrieval fetches facts into context 10 Test-time search sample · rank · tree 11 Solver / verifier tool checks what the model proposes Answer or action tokens base weights aligned weights response 03 Bayesian opt. tunes η, batch, width 02 Evolutionary searches architectures Eval harness scores the outputs hyperparameters candidate designs · rare reward signal 14 Diffusion branch parallel · image, audio, structure out not on this path: 07 · 12 · 13 · 17
A frontier language or multimodal system, 2026. Green-bordered nodes are the three primitives nearly every such system depends on; dashed nodes are present in some systems and absent in others. Cellular automata, explicit Bayesian inference, state estimation and boosted trees do real work elsewhere but are not on this path.

Primitive map

All seventeen, grouped by family around the center. Faint lines are the pairings from the sheets below; hover any primitive to light up what it combines with, click it to jump to its sheet.

Families as spokes, primitives as leaves; the dashed leaf is the open slot for a growth-based primitive.

How the families combine

Read a row as "this family, used with that one." Native means one is routinely built on the other; common means a well-trodden combination; rare means it happens, but you would have to argue for it.

NativeCommonRare

The empty slot

Every sheet above shares a set of quiet assumptions. A leaf that grows itself into the shape of its neighbor breaks each of them. Listing the inversions is the fastest way to say what a plant-derived primitive would have to be, in language a lab would accept.

The canon assumesThe plant does insteadNearest existing sheet
A model separate from the body it controlsThe body is the model; the trained structure is the organism07 Cellular automata
A global objective and a central error signalLocal-only signals; every cell sees its neighbors and the light on its own surface07 Cellular automata · 01 (local rules only)
Reversible parameter updatesIrreversible growth; a leaf cannot be un-grown, only abandoned03 Bayesian optimization
Cheap samples, many of themCostly committed samples, few of them, paid for in carbon and water03 Bayesian optimization · 02 Evolutionary
Sensing, then actingSensing by growing; the action is also the sensor13 Active inference
The ability to simulate forward before committingNo forward model; hedge structurally by keeping modules redundantnone (MCTS has no plant analogue)
Fast discrete stepsSlow continuous developmental time; the clock is the season05 Recurrence · 13 State estimation
Working name for the primitive

Shape matching under local-only sensing with irreversible, resource-limited growth.

Parents on the shelf

Neural cellular automata for the local-rule body, evolutionary search to find the rule, Bayesian optimization for the budgeted sampling, active inference for sensing-as-acting.

What would make a lab adopt it

Not a metaphor but a benchmark: a target silhouette, a light field, a cell population, a carbon budget, and a score. Ship the environment; the biology is the ground truth that keeps it honest.