perf: derive array capacity from mi_usable_size

[TwoFX]

No description provided.

[TwoFX]

!radar

[leanprover-radar]

Benchmark results for a221d7d against ac0f56e are in. There are significant results. @TwoFX

• 🟥 build//instructions: +32.4G (+0.29%)

Large changes (3✅, 3🟥)

• ✅ compiled/ilean_roundtrip//instructions: -231.8M (-1.06%)
• ✅ compiled/ilean_roundtrip//maxrss: -28MiB (-5.40%)
• 🟥 compiled/nat_repr//instructions: +2.4G (+7.20%)
• 🟥 compiled/phashmap//instructions: +81.5M (+0.93%)
• 🟥 compiled/unionfind//maxrss: +20MiB (+19.88%)
• ✅ elab/bv_decide_mul//maxrss: -60MiB (-6.13%)

Medium changes (3✅, 3🟥)

• 🟥 compiled/parser//instructions: +241.9M (+0.68%)
• 🟥 compiled/qsort//instructions: +16.5M (+0.11%)
• 🟥 elab/big_do//instructions: +87.7M (+0.48%)
• ✅ elab/bv_decide_mul//instructions: -300.9M (-0.93%)
• ✅ interpreted/iterators//instructions: -42.0M (-0.12%)
• ✅ misc/leanchecker --fresh Init//maxrss: -10MiB (-1.95%)

Small changes (4✅, 102🟥)

• 🟥 build/module/Init.Core//instructions: +33.3M (+0.34%)
• 🟥 build/module/Init.Data.Array.Attach//instructions: +62.1M (+0.61%)
• 🟥 build/module/Init.Data.Array.Basic//instructions: +37.3M (+0.35%)
• 🟥 build/module/Init.Data.Array.Erase//instructions: +31.6M (+0.45%)
• 🟥 build/module/Init.Data.Array.Find//instructions: +65.3M (+0.68%)
• 🟥 build/module/Init.Data.Array.Lemmas//instructions: +267.4M (+0.51%)
• 🟥 build/module/Init.Data.Array.Lex.Lemmas//instructions: +38.3M (+0.41%)
• 🟥 build/module/Init.Data.Array.MapIdx//instructions: +42.6M (+0.49%)
• 🟥 build/module/Init.Data.Array.Monadic//instructions: +29.4M (+0.49%)
• 🟥 build/module/Init.Data.BitVec.Bitblast//instructions: +204.0M (+0.41%)
• 🟥 build/module/Init.Data.BitVec.Lemmas//instructions: +460.0M (+0.40%)
• 🟥 build/module/Init.Data.ByteArray.Lemmas//instructions: +25.1M (+0.46%)
• 🟥 build/module/Init.Data.Fin.Lemmas//instructions: +47.2M (+0.44%)
• 🟥 build/module/Init.Data.Int.DivMod.Lemmas//instructions: +185.3M (+0.50%)
• 🟥 build/module/Init.Data.Int.Gcd//instructions: +23.9M (+0.54%)
• ✅ build/module/Init.Data.Iterators.Consumers.Total//instructions: -23.0M (-2.40%)
• 🟥 build/module/Init.Data.Iterators.Lemmas.Combinators.Append//instructions: +13.6M (+0.46%)
• 🟥 build/module/Init.Data.Iterators.Lemmas.Combinators.FilterMap//instructions: +108.9M (+0.58%)
• 🟥 build/module/Init.Data.Iterators.Lemmas.Combinators.FlatMap//instructions: +30.2M (+0.47%)
• 🟥 build/module/Init.Data.Iterators.Lemmas.Combinators.Monadic.FilterMap//instructions: +162.9M (+0.46%)
• and 86 more

[TwoFX]

Instructions are up 0.3%, cycles, wall-clock and task-clock are all down 0.3%

[leanprover-bot]

Reference manual CI status:

• ❗ Reference manual CI can not be attempted yet, as the nightly-testing-2026-08-30 tag does not exist there yet. We will retry when you push more commits. If you rebase your branch onto nightly-with-manual, reference manual CI should run now. You can force reference manual CI using the force-manual-ci label. (2026-08-31 10:42:26)

[mathlib-lean-pr-testing]

Mathlib CI status (docs):

• ✅ Mathlib branch lean-pr-testing-14979 has successfully built against this PR. (2026-08-31 12:11:49) View Log