* Fix bitsandbytes ROCm GPU arch and warp size detection on Windows
bitsandbytes resolves the ROCm GPU architecture (and warp size on
0.49.x) by shelling out to rocminfo / hipinfo.exe via PATH at import
time. On Windows neither tool is normally on PATH (AMD torch wheels
ship hipInfo.exe into the venv Scripts dir, only on PATH while
activated), so every `import bitsandbytes` logs an ERROR and WARNING,
ROCM_GPU_ARCH degrades to unknown, and the 0.49.x warp size defaults
to 64, which is wrong on RDNA (wave 32) and silently disables
pre-quantized 4-bit models via ALLOW_PREQUANTIZED_MODELS.
Install a one-shot MetaPathFinder before unsloth_zoo is imported (the
first bitsandbytes import on ROCm) that swaps get_rocm_gpu_arch and
get_rocm_warpsize for torch-device-properties-first implementations
right after bitsandbytes.cuda_specs executes, before cextension reads
them. Falls back to running hipInfo.exe by absolute path (venv
Scripts, conda Scripts, HIP SDK / AMD installer dirs). Repairs the
constants in place when bitsandbytes was imported first. Strict no-op
on non-Windows, non-ROCm builds, missing bitsandbytes, and versions
that fix this upstream. Opt out with UNSLOTH_DISABLE_BNB_ROCM_FIX=1.
Proposed upstream in bitsandbytes-foundation/bitsandbytes#1969;
shipped here so all bitsandbytes versions are covered. Verified on
gfx1151 Strix Halo, Windows 11, torch 2.11.0+rocm7.13.0 against
bitsandbytes main, 0.49.2, and a torch-props-fixed variant.
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* Tighten comments in the bitsandbytes ROCm detection fix
Comment and docstring pass only. AST comparison with docstrings
stripped confirms every definition is identical to the version the
12 scenario suite ran against, and the suite plus the drift test
pass unchanged on the edited files.
* Keep the bitsandbytes cuda_specs finder installed for reload support
Simulation testing caught a regression in the one-shot design:
importlib.reload(bitsandbytes.cuda_specs) re-resolves the spec through
sys.meta_path, so with the finder already removed the reload reinstalled
the unpatched upstream detector and the Windows ROCm noise returned.
Keep the finder on sys.meta_path permanently, matching the lifecycle of
the existing causal_conv1d and vllm import blockers. The finder matches
a single module name and patching stays idempotent via the sentinel
flags, so repeat hits are no-ops.
Validated on gfx1151 Windows 11: 22 simulation scenarios (conda and
embedded layouts, Program Files scan ordering, paths with spaces and
unicode, hanging probe timeout, lru-wrapped and C-function helper
shapes, reload, failed-import retry, threads, spawn, dormant finder,
Studio PATH coexistence, early fix-block ordering, bnb 0.45.5 / 0.47.0
/ 0.49.2 / main / upstream-fixed) plus the original 12 scenario suite,
CPU-torch and stale-HIP_PATH sandboxes, Python 3.10 to 3.13 gates, and
a WSL Linux leg proving byte-identical Linux behavior with and without
the fix, with and without rocminfo on PATH.
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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
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