Linux offscreen capture (EGL/GLES pbuffer; llvmpipe in the sandbox) and an opt-in screen-space gate
for LOD>=3 (normal distance projected at each LOD's closest display distance, 1 px at 1440p =
0.61 mrad). The gate rejects the S13 octave-drop and stride-2 controls, fault injections, and a
vertical-vs-screen control. Finding: today's far meshes differ from the field by up to 92 px, and
LOD swaps snap mesa rims by tens of px (p50 0 px), a silhouette effect of plain LOD switching. The
octave cutoff was dropped: nothing qualified, and octaves are a small share of far time. Off-path
cost: reviewer interleaved W12 within noise vs L4 (+0.6% median). Hashes = L4.
Largest far lever measured: column work outside noise, 34% of far worker time (duplicate XY across tiles).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ED33VnqepD4YY6gDAAA832
CoreNamespacePreamble.h applies per-compiler contraction-off pragmas (Clang, MSVC, GCC; unknown
compiler = #error) and a fused-multiply-add self-test that World::compile runs before building.
Clang -ffp-contract=on and GCC's default (fast) now reproduce the L1/Windows hashes (they diverged
in L2); Clang -ffp-contract=fast ignores the pragma and is refused at startup (negative control).
Seed sweep with every cube on real terrain: 48 seeds x 2 recipes x 3 builds x W1/W12, 576 runs,
0 mismatches, 0 empty meshes. Cost +0.5% (2.326 -> 2.337 s, interleaved). World unchanged.
MSVC/UBT not compiled here: Windows to-do list in Linux3/REPORT.md.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Clang -ffp-contract=on/fast and GCC's default (fast) all change the density hash on the L1 view;
contraction off reproduces L1 (= Windows S13) at W1/W12. Seed sweep: 48 FloatingIslands seeds and
14 effective SurfaceWorld seeds (34 of 48 fell on a seed-independent cube) match across Clang/GCC
and W1/W12. Standalone gains --seed/--recipe/--render-distance-chunks (viewer + headless) and a
Windows replay script. Linux standalone workers get 32 MiB pthread stacks (TLS is 17.3 MiB/thread),
so no external stack limit is needed. No Core or world-output change; MSVC compile unverified.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Headless Linux benchmark/hash tool (Clang 19 / GCC 14) sharing the viewer's plan builder and
streaming pipeline (moved verbatim into StreamBenchmarkPipeline.h / WorldAssemblyPrototype.h).
Owner Round17 view: density/mesh/payload/topology hashes equal the Windows S13 reference at
W1/W8/W12 (Clang, 3 runs each) and W8 (GCC), with -ffp-contract=off. No output change.
Baseline (i9-12900H, CPUs 0-11, powersave/balance_performance): whole view W8 3.562 s median,
W12 3.512 s, W1 16.555 s; peak RSS < 605 MiB.
Review: the default-stack crash is 17.3 MiB of static TLS per thread (glibc puts it in the
thread stack; HeightfieldColumnCache 6.8 MB), not recursion -- open, after S14.
MSVC compile of the viewer refactor not verified (no MSVC here).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Fr0zkaandClaude Opus 5.5