I was just starting a new project, like I normally do, and tried installing pymc like this: conda create -n multinom3 python=3.12 pymc=5.21.0 arviz jupyter -c conda-forge This is on windows 11. Note I pinned these versions only in later experiments when I could not get defaults to work either. …

Tracking this in GitHub in Pytensor finds wrong compiler on windows when `libgcc>15` is installed · Issue #1398 · pymc-devs/pytensor · GitHub

Can you post versions for pymc and pytensor? (or just confirm they are both the latest releases as shown on the github page) Edit: Just noticed you’re version pinning pymc – is that necessary? You might need an associated pin on pytensor.

The pins are not necessary, I was just ‘trying things’ to get it to work. Pytensor version was 2.28.2 (I also tried 2.28.3)

Just to clarify I also tried to create a fresh environment following the instructions on the pymc website and got the same errors. (with default versions for all) . I tried many things lol, and one thing I found that definitely worked is switching over to my MacBook for the time being :wink:

By the way, I don’t think those differences you posted should be the determining factor. Those look like C++ runtimes, but your error is happening at the pytensor level, before the logp function is compiled.

Ok thanks! Here is more of the error message if it helps: Initializing NUTS using jitter+adapt_diag... ERROR (pytensor.graph.rewriting.basic): Rewrite failure due to: constant_folding ERROR (pytensor.graph.rewriting.basic): node: Cast{float64}(0) ERROR (pytensor.graph.rewriting.basic): TRACEBACK: E…

If there are other tests you can think of that i could try, I would appreciate it!

Well now I do think those differences could be relevant. Just to rule it out, could you clear your pytensor cache (pytensor-cache clear )

Ok tried that, still same errors. also did purge just to be sure.

The compiler / path machinery is failing, may be a general incompatibility with a recent version of windows 11? Don’t know if other folks out there have succeeded installing PyMC on recent Windows 11. Perhaps @michaelosthege ?

In the meantime you can try to avoid the C backend. Set pytensor.config.cxx="" and for sampling with PyMC use the numba backend by passing compile_kwargs={mode:"NUMBA"} or use the nutpie sampler which also defaults to numba.

Wierd problem installing PYMC

Questions v5

DrEntropy May 13, 2025, 7:24pm 18

Thanks, for anyone else reading this, it was fixed with Remove iostream include for C backend by maresb · Pull Request #1400 · pymc-devs/pytensor . Thanks @maresb !

All models on Windows don't sample or sample at impossibly slow speed

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Wierd problem installing PYMC

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