Refactor iter

[OutSquareCapital]

Main goal

Improve sortedcontainers iterators speed. ALL sortedcontainers call SortedList.__iter__() internally, hence this change will apply to all of them.

for a code equivalent to tuple(iter(SortedList(range(n)))), here are the new numbers with this PR.

size is the nb of items in the Iterator and the number below each library is the median duration in microseconds to complete the task.

size	relative
10	2.123
100	1.66
1000	1.442
10000	1.3665
100000	1.344

With reversed iterator:

size	relative
10	2.192
100	1.473
1000	1.3555
10000	1.4155
100000	1.279

Other changes

• a full revamp of benchmark CLI for much more convenient runs and analysis
• CI checks jobs on github are now much faster with cache use and reduction of redundant work
• deduplicated a lot of code
• In general for sortedcontainers, less pointers indirection since we don't need Arc anymore as much
• AI policy guidelines
• Architecture documentation

NOTE:
tried to use copilot review. Can catch some useful issues but lot of false positives on polars behavior, and overall greptile is much better. I don't have any money to spend for that left anyway lmao.

[Copilot]

Copilot review overview

🟡 Changes recommended

The release panic setting can terminate the Python process on user-triggered errors.

Review effort: Balanced
Findings: 1

Open (1)

• Release panic aborts process on range overflow · New

Resolved since last review (5)

• Stop reverse slicing when cursor passes the lower bound
• Prevent re-entrant iterator access during collection mutation
• Avoid aborting Python on comparison failures
• Invalidate cached failure indices when invocation changes
• Allow missing timestamps in commit-group summaries

Previously missed (2)

In code that hasn't changed since last review

Exhausted iterators resume after collection mutation

crates/​sorted_rs/​src/​iter/​core.rs:57

Both forward and reverse null-return paths leave the cursor unchanged, so collection mutations can revive an exhausted iterator. For example, exhaust iter(SortedList([1])) through StopIteration, then add 2: the next call yields 2. Likewise, create a reverse iterator, clear its collection, observe StopIteration, then repopulate it: iteration resumes. Python iterators must stay exhausted. Record a permanent terminal state in both paths, and test mutation after StopIteration; additions before the first exhaustion check should still work.

Cache reuses failure index after command changes

scripts/​checks.py:53

The cache stores only a failed index, so changing --slow does not reset it as promised by the CLI help. For example, a fast-mode failure at index 3 is reused by the nine-command slow run because 3 < 9, skipping the earlier checks. Adding or reordering commands can also reuse the wrong index. Store a command-list signature alongside the index and restart at zero when the signature changes.