# Optimization ledger — one row per variant, never delete a row

The point: a promising optimization abandoned over a *fixable bug* is the most common way to leave 2x
on the table. So the "why dropped" column distinguishes **slower** from **merely broken**. Anything
marked `broken` is a candidate to revisit, not a dead end.

Keep the last-known-good runnable at all times.

| # | variant | correct? | metric | vs best | status | why dropped |
|---|---|---|---|---|---|---|
| 0 | reference (spec) | yes | — | 1.00x | baseline | — |
| 1 | naive port | | | | | |
| 2 | + shared-mem tiling | | | | | |
| 3 | + async copy / TMA | | | | | |
| 4 | + warp specialization | | | | | |
| 5 | shape-specialized dispatch | | | | | |

status ∈ {best, kept, slower, **broken**, untested}

## Time attribution — where the remaining time goes

Update after each profile. Attack the largest row; never stop because a percentage looks good.

| component | us | % of total | bounded by | idea |
|---|---|---|---|---|
| | | | | |