why does conda update downgrade some libraries

Question

For m, on OS X, conda update --all often downgrades libraries - along with updating many.

Is this usual? Or something possibly in my setup?

Earlier this year, it was pillow for many months.

Surprisingly, today it was several of the HDF5 related libraries, numba and llvmlite.

So conda update numba brings numba back to the most recent version, and so on with the other 8 libraries, but why doesn't conda update --all do this anyway?

Answer 1

It's a compatibility issue. Anaconda is a stable set of packages. When you update Anaconda, you update to this stable list.

However, when you update individual packages, they might cause incompatibility issues with the rest of the Anaconda distribution so they aren't considered stable. That's why when you use conda update --all, it gets you to the latest stable Anaconda distribution, which might or might not have the version of the individual package you wanted.

See here: https://github.com/ContinuumIO/anaconda-issues/issues/39

Edit: This behavior has changed. It now tries to increase the version of all packages (except Python between major/minor version) such that no packages will be incompatible with each other.

See here: http://continuum.io/blog/advanced-conda-part-1#conda-update-all