fix(hmc): forward dtype to QuadPotentialDiagAdapt in default potential creation#8280
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fix(hmc): forward dtype to QuadPotentialDiagAdapt in default potential creation#8280xodn348 wants to merge 1 commit into
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…l creation BaseHMC.__init__ accepts a dtype parameter and passes it to the parent class, but omits it when constructing the default QuadPotentialDiagAdapt. This causes the potential to silently fall back to pytensor.config.floatX even when the caller explicitly requests a different dtype. Fixes pymc-devs#8213
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Summary
BaseHMC.__init__accepts adtypeparameter and correctly forwards it to the parent class, but silently drops it when constructing the defaultQuadPotentialDiagAdapt. The potential therefore always falls back topytensor.config.floatX, ignoring the caller's explicitdtyperequest.One-line fix: add
dtype=dtypeto theQuadPotentialDiagAdapt(...)call inbase_hmc.pyline 169.Issue
Fixes #8213
Local verification
Verified against pymc 5.28.5 with the patch applied to the installed package.
Three tests were run:
pm.NUTS(dtype="float32").potential.dtype == np.dtype("float32")— passes after fix, would fail before.pm.NUTS().potential.dtype == np.dtype(pytensor.config.floatX)— backward-compatibility preserved.pm.HamiltonianMC(dtype="float32").potential.dtype == np.dtype("float32")— same fix coversHMCsince both useBaseHMC.Risk
Low. Single-argument addition to an existing constructor call. The behaviour for
dtype=None(the default, used by virtually all existing code) is unchanged —QuadPotentialDiagAdaptalready defaults topytensor.config.floatXwhendtypeisNone.