ht: fuse keys/values arrays into a single entries array (fixes #84) - #96
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Replace the separate keys and values backing arrays in ttak_map_t and
ttak_table_t (keys/key_lens/values) with one fused entries array of
{key, value} pairs, keeping ctrls separate so probing logic is unchanged.
A successful lookup now touches at most two cache lines (ctrl byte +
entry) instead of three (ctrl byte + key line + value line).
Tombstone tracking from 80447e7 is preserved: deletes still mark slots
DELETED and bump the tombstone count, inserts reuse the first tombstone
slot on the probe chain and decrement, and rehash-in-place/growth still
clears tombstones by rebuilding from live entries only. The two mem.c
iterations over the global ptr map now read entries[i].key instead of
keys[i]. Public API is unchanged.
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Summary
keys/valuesbacking arrays (andkey_lensfor the generic table) into a single fusedentriesarray of{key, value}pairs in bothttak_map_t(include/ttak/ht/hash.h) andttak_table_t(include/ttak/ht/table.h), keepingctrlsas a separate array so the probing logic is untouched.DELETED+ bumps the tombstone count, insert reuses the first tombstone slot on the probe chain and decrements, and rehash-in-place/growth still clears tombstones by rebuilding from live entries only.src/mem/mem.citerations over the global ptr map readentries[i].keyinstead ofkeys[i].Benchmark
Random lookup throughput on a 1M-entry
tt_map_t(capacity 2^21, ~50% load), 10M random lookups per rep, best-of-9 / median-of-9 reps,clock_gettime(CLOCK_MONOTONIC), same bench binary linked against the pre-change lib (95854ca) and the new lib:~2% better best-case and ~4% better median lookup latency. The absolute numbers are inflated by per-call
ttak_mem_access()overhead in the public map API; the structural cache-miss reduction (3→2 lines per hit) is the intended win and shows up consistently in best-case latency.Full
make testsuite passes on the branch.Not merged — leaving for review.