Playground

Try matten’s shape reasoning below — broadcasting, reshape, axis reductions, matrix multiplication, and converting mixed data to numeric — computed by a real build of core matten and shown exactly as it happens, including rejections.

A zero-sized dimension — a shape like 3,0 — is a valid input here. It looks like it should fail, but matten accepts zero-sized dimensions (RFC-111): try it in any of the four forms below and the result computes normally, including a matrix product where one side has a zero dimension.

Rejections are shown, not hidden

Try an incompatible pair — shapes 2,3 and 4 for broadcasting, or 2,3 and 2,2 for matmul — and the page shows the same error matten itself produces for that mistake, not a generic “invalid input”. A rejected operation teaches as much as an accepted one.

Input notes

A shape or values field accepts either commas or newlines as separators — paste a grid the way it looks, one row per line, and it parses (1, 2, 3 on one line and 1, 2, 3\n4, 5, 6 across two both work). A trailing separator is always fine (1,2,3, is the same as 1,2,3).

A blank cell in the middle of a shape or values field — 1,2,,4 — is never silently dropped. On the four numeric forms above it is reported by position, since a numeric tensor has no way to represent “missing” and dropping it would silently shift every value after it. On the Converting mixed data form it is accepted and shown as None instead — a dynamic tensor can represent a missing cell, so there it is data to convert or reject explicitly, not a parsing mistake.

Notes for contributors

Building the WebAssembly module locally

This page needs a WebAssembly build that a plain local mdbook build does not produce. The .wasm module and its JS bindings are generated by a separate step and are git-ignored, not committed — the same policy this workspace already applies to tools/matten-report/tools/matten-migrate/benchmarks’s own Cargo.lock files: build artifacts of a workspace-excluded, publish = false tool are regenerated on demand, not tracked. Build it first:

cargo build --manifest-path tools/matten-playground/Cargo.toml \
  --target wasm32-unknown-unknown --release
wasm-bindgen --target web \
  --out-dir docs/src/playground \
  --out-name matten_playground \
  tools/matten-playground/target/wasm32-unknown-unknown/release/matten_playground.wasm

Then mdbook build docs (or mdbook serve docs) as usual. In CI this happens automatically before every book build (.github/workflows/docs.yaml) — a checkout from main and a fresh mdbook build locally are the only two cases that need the manual step above.

The scope rule

The output on this page is a representation, never a visualization, of what matten computes (RFC-093 §6, as amended by RFC-095 §3):

• Representation (permitted): showing the tensor’s own structure — rows as rows, columns as columns, numbers as numbers. This is how mathematics writes a matrix and how NumPy prints one. It adds no information that is not already in the shape and the values.
• Visualization (forbidden): encoding a value as visual magnitude or colour — bars, sparklines, heat maps, axes, lines, colour scales, SVG, canvas. Forbidden regardless of the medium, including plain characters: a bar chart drawn with # is visualization and stays out of scope.

The test: does the rendering encode a value as something other than that value? A grid does not. A bar does, however it is drawn. A change that crosses this line needs its own RFC that argues against RFC-093 §6 by name.