The whole-run passes retain every frame's integrated reflections until scaling is done - thousands
of vectors of a few megabytes each, allocated by the image workers in the allocator's per-thread
arenas. When a pass hands them back, most of that memory stays in those arenas as holes, and the
next pass's workers (new threads) do not reuse it, so on a fine-sliced long axis gigabytes of freed
reflections were carried to the end of the run.
IndexAndRefine now copies each retained frame's reflections into a ReflectionArena: 64 MiB blocks,
each its own mapping, carved by a bump pointer and returned to the system in one piece when the
last vector in them is gone. IntegrationOutcome::reflections becomes a std::vector with an allocator
that uses the arena when given one and plain new/delete otherwise (copies go to the heap), so the
read sites are unchanged; the few functions that took the vector by type now take a span.
No arithmetic changes; merged output byte-identical.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013nW6FNRP1bBJJ8pfHiByAT
