**System Information**
win7 x86/x64
**Blender Version**
Broken: latest master
Worked: (optional)
**Short description of error**
There's noise differences between the reference image and the render output, more interesting there's also a noise difference between win32 and win64, just re-generating the reference image does not make this test pass on both platforms. Throwing more samples at it also doesn't solve the issue (tried with up to 5000 samples)
||win32|win64|reference|
||{F4384165}|{F4384168}|{F4384170}|
|difference from reference|{F4384175}|{F4384179}||
**Exact steps for others to reproduce the error**
example images done with `tests\render\ctests\hair\principled_hair_directcoloring.blend` but `principled_hair_melaninconcentration.blend` and `principled_hair_absorptioncoefficient.blend` fail for the same reason.
in debug mode all crash during the test hitting the following assert
```
59: Assertion failed: fabsf(dot(X, Y)) < 1e-4f, file k:\blendergit\blender\intern\cycles\kernel\closure\bsdf_hair_principled.h, line 299
```