* Clear ALLOW_BITSANDBYTES when the bitsandbytes native kernels are not real
From bitsandbytes 0.46 a wheel whose native library never loaded still imports and
resolves every ctypes handle: BNBNativeLibrary.__getattr__ returns a throw_on_call
closure, and a dead library is replaced wholesale by ErrorHandlerMockBNBNativeLibrary,
which does the same for every name. Nothing raises while kernels/utils.py binds them
at module scope, so device_type.py's guarded import sees a healthy wheel,
ALLOW_BITSANDBYTES stays true, loader.py forwards the default load_in_4bit=True and
the run dies inside a kernel instead of degrading to 16bit.
Probe the handles the kernels actually bind and clear the flags when they are not
native. A real handle is a ctypes function pointer and carries restype; a deferred
failure is a Python function and does not.
Scoped to the capability flags on purpose. The module stays bound and get_ptr keeps
pointing at bitsandbytes, because these shapes import perfectly well and treating
them as absent would disable a wheel whose Python side works - a CPU-only install is
exactly that shape.
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Only clear the flags when the native library is dead, not partially exporting
ALLOW_BITSANDBYTES gates 8bit as well as 4bit - loader.py:505-510 clears both - so
failing the check on one missing 4bit symbol would silently downgrade an otherwise
valid LLM.int8 request to 16bit. A library that exports some of these handles is
alive; only one where none of them is a ctypes function pointer is dead, which is
the CPU-only and ErrorHandlerMockBNBNativeLibrary case this exists for.
A genuinely missing symbol raises where kernels/utils.py binds it, so it is a crash
no capability flag can rescue and not something to trade 8bit for.
* Gate the bitsandbytes ctypes binds on the same verdict as the flags
Clearing ALLOW_BITSANDBYTES is not enough on its own. kernels/utils.py guarded
the bnb.functional.lib.* binds on `bnb is None` alone, so an importable but dead
wheel still reached them at module scope: bitsandbytes 0.45.5, the floor in
pyproject.toml, sets functional.lib = None when the native library fails to load,
and None.cdequantize_blockwise_fp32 raises right there. That kills import unsloth
outright instead of degrading to 16bit, which is the fallback the cleared flag
exists to reach.
Reuse native_kernels_ready so the bind path and the flag path agree, and take the
_bnb_required branch when they say the library is dead. Touches only the guard
expression, not the binds themselves.
* Tighten the comments on the bitsandbytes kernel readiness probe
* Require every probed handle, and license the module Apache like the rest of unsloth
The readiness verdict now gates the module-scope ctypes binds as well as the flags,
so "at least one handle is native" is no longer the right question. A library that
resolves one symbol and not another passed the probe and then raised AttributeError
at the bind the probe exists to prevent. Require all of them.
That costs 8bit in the partial case, since ALLOW_BITSANDBYTES gates both, but a wheel
missing a symbol is a shape no flag can make safe and refusing it beats crashing on
it. Flipped the test that encoded the old behaviour and added the more realistic
shape: the library loaded, one symbol is still a deferred-failure closure.
LICENSE:190 assigns files under unsloth/* to Apache 2.0, and 87 of the 90 modules
there carry that header, so use it here rather than AGPL.
* State the all-handles rule once instead of three times
---------
Co-authored-by: danielhanchen <unslothai@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
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