Joseph Ferano
b2059520ab
BUILT.md gets the Map and the defer relaxation; NEXT.md strikes step 4 and item 3, and records four things that are genuinely open rather than finished. The one worth reading is that the Map is slower than CPython's dict at a million entries while being six times quicker cache-resident. Both are memory-bound at that size and this layout waits longer: keys, values and hashes are three separate runs, so a lookup that misses everything costs three cache misses where a compact dict costs two, and the hash run is a full eight bytes a slot. Cell packing buys probe locality, which is a win while the hash run is resident and a loss once nothing is. One byte of metadata a slot is the known answer and is not built, and the crossover between the two results is somewhere nobody has looked. Also recorded: the defer change amends a frozen spec-memory.md, which said a defer for a let-bound value was not expressible; and the Map is narrower than the spec on one point, a fixed array being a key only when its elements compare bytewise.
