# PyMC V4 install issue: WARNING (Using NumPy C-API based implementation for BLAS functions

**URL:** <https://discourse.pymc.io/t/pymc-v4-install-issue-warning-using-numpy-c-api-based-implementation-for-blas-functions/9621>\
**Category:** v5\
**Created:** [June 12, 2022, 2:57am UTC](https://discourse.pymc.io/t/pymc-v4-install-issue-warning-using-numpy-c-api-based-implementation-for-blas-functions/9621 "2022-06-12T02:57:34Z")\
**Posts on this page:** 1\
**Showing post:** 13

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**Author:** ![CameronBieganek](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.pymc.io/cameronbieganek/32/5276_2.png) [@CameronBieganek](https://discourse.pymc.io/u/CameronBieganek)\
**Post date:** [June 18, 2022, 2:23pm UTC](https://discourse.pymc.io/t/pymc-v4-install-issue-warning-using-numpy-c-api-based-implementation-for-blas-functions/9621/13 "2022-06-18T14:23:02Z")

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Possible solution described here:

> [@WARNING: g++ not detected](https://discourse.pymc.io/t/warning-g-not-detected/9661/3):
>
> I managed to accidentally resolve this issue. I recently updated my operating system from an old version of macOS to the new macOS Monterrey. I was occasionally getting what seemed like an unrelated error when using the terminal (not the python REPL): xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun I was able to resolve that by running xcode-select --install in the terminal, as described in t…

In short, you might need to install/re-install `xcode-select` via the following terminal command:

```plaintext
xcode-select --install

```

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_[View the full topic](https://discourse.pymc.io/t/pymc-v4-install-issue-warning-using-numpy-c-api-based-implementation-for-blas-functions/9621)._