For the complete documentation index, see llms.txt. Markdown versions of all pages are available by appending .md to any URL (e.g. /get-started.md).

Mojo module

rowwise

CPU row-wise reduction scaffolder.

Mirrors the body-facing surface of algorithm.gpu.rowwise so the same body[params: ContextParams](row_coords, mut ctx) works for both targets. Reuses GPU's ContextParams / Context types verbatim; the GPU-only runtime fields (split-K pointers and counters) get sentinels and are never read.

Tier mapping CPU ↔ GPU:

• Inner-axis cooperative (emit_tile_width == 1, axis == rank - 1): one worker per row, vectorize the row at simd_width. Mirrors the GPU block tier with BLOCK_SIZE = 1.
• Non-inner-axis tiled (emit_tile_width > 1, supports_tiled): one worker per slice; tile the innermost-non-axis dim with W = simd_width independent accumulators. Mirrors the GPU tiled tier.
• Non-inner-axis cooperative (emit_tile_width == 1, !supports_tiled): one worker per output, scalar walk over the reduce axis. Mirrors the GPU cooperative-non-inner tier.

pjoin is a no-op on CPU and once runs unconditionally: one worker owns each output, so the monoid state is already final after reduce.

Structs

• ​SerialReducer: Single-participant Reducer for CPU's serial / cooperative tier. Nothing to combine across (one worker per output), so sum/max/min/generic are identity. Routing cpu_rowwise.pjoin through it rather than skipping the call still invokes the monoid's own pjoin body, which may do per-state finalization (e.g. ReduceSum horizontally reducing its SIMD-wide accumulator into the scalar acc field exposed to bodies).

Functions

• ​launch: Top-level CPU scaffolder. Picks the tier from axis and supports_tiled, parallelizes over outputs (or output tiles), and invokes the body once per output (or tile).
• ​once: CPU: runs emit unconditionally on the cooperative / tiled tiers (one worker per output), or gated on ctx._is_last_block on the split-axis tier (only the last-arriving worker emits).
• ​pjoin: CPU: drives the monoid's pjoin body via SerialReducer in the cooperative tier, or merges the cross-worker partials buffer in the split-axis tier.
• ​reduce: Drives tile_fn over the reduce axis, CPU-side, with no monoid state — pure per-tile iteration for map/emit terminals (see the state-carrying overload below for reduce phases).