Annotations

Put an annotation comment on the line above the declaration:

// @viscosity soa        transform (if safe), even if small or loop-free
const particles = [];

// @viscosity aos        never transform this one
const ui = [];

// @viscosity aosoa(8)   blocks of 8, field-major within a block
const grid = [];

Annotations never override safety: an annotated collection that isn’t provably safe is still left alone, with the reason. aosoa requires every field to be numeric. Its block size must be a power of two from 2 to 65536 (a plain aosoa, without parentheses, means 8); any other size, such as aosoa(12) or aosoa(x), keeps the collection as objects, and explain says why (see Errors and validation).

In --mode opt-in, only annotated collections are considered at all.

In Python, write # @viscosity soa on the line above xs = [].