tiny-gpu

Live

A GPU simulator you can step through, with threads drawn as heatmaps while a kernel runs.

Explore the idea.

Three small kernels on eight threads, stepped the way the simulator steps them. Pick a kernel, then step through it. This sketch runs the same algorithm in JavaScript. The simulator in the repo is the real thing.

Interactive illustration · Simplified model

What it shows.

Each thread has its own registers. Shared memory lets threads in a block read each other's values, and barriers make every thread wait until the rest arrive.

The frames below are the simulator's own output, captured mid-run for three kernels.

Three kernels, captured mid-run.

Frames from the simulator's own output, not drawn for this page.

Vector add: Each thread adds one pair of numbers, with registers and memory updating every cycle. — **Vector add.** Each thread adds one pair of numbers, with registers and memory updating every cycle.

Reduce sum: Threads combine partial sums in shared memory until one value is left. — **Reduce sum.** Threads combine partial sums in shared memory until one value is left.

Odd-even sort: Threads swap neighbours in passes, with the program counter shown per thread. — **Odd-even sort.** Threads swap neighbours in passes, with the program counter shown per thread.