Same here. I also am interested in more background on the fork. Theano
itself was supposed to be "dead" a few years ago when the original
developers stopped working on it, but then the pymc developers picked
up maintenance. 

The PyMC group are also maintainers of the original Theano repo, but, per 
request of the original maintainers, we are not making changes to the 
Theano repo. The Theano repo really should be frozen, but I'm assuming that 
we're leaving that up to the original maintainers. 

Could the same thing happen again?

Could development stop on Aesara as it did with Theano? If that's the 
question you're asking, the answer is that it's always possible, but 
unlikely to occur any time soon. There's still a real place for a primarily 
Python-driven tensor library with a (relatively) accessible codebase. Also, 
for PyMC's purposes and future, we need to work more and more at the tensor 
library level, so it's important that the development requirements not 
skyrocket, and that the underlying library not make detrimental design 
and/or implementation changes.

Also, I had heard that pymc was dropping theano in favor of tensorflow
(do I remember this correctly?). Is this still planned, or has that
changed to be aesara now?

Since this announcement 
<https://pymc-devs.medium.com/the-future-of-pymc3-or-theano-is-dead-long-live-theano-d8005f8a0e9b>,
 
we've dropped all plans to implement the next version of PyMC in 
TensorFlow. The reason: it's possible for us to have the kind of tensor 
library described above *and* use other backends, when desired. I wrote a 
quick example of how we can convert Theano graphs to JAX "graphs", and that 
was enough to prove the point.

My original plan was to use SymPy for all this, but it would've resulted in 
a distinct project anyway, because doing all that work via changes to SymPy 
would've most likely taken too long.
On Monday, March 15, 2021 at 5:34:27 PM UTC-5 [email protected] wrote:

> On Mon, Mar 15, 2021 at 4:18 PM Oscar Benjamin
> <[email protected]> wrote:
> >
> > On Mon, 15 Mar 2021 at 22:01, Aaron Meurer <[email protected]> wrote:
> > >
> > > As long as Theano itself still works in versions of Python that SymPy
> > > supports, it would be better to deprecate the function rather than
> > > just remove it. The function theano_code is public API so just
> > > removing it would be a backwards compatibility break, which we try to
> > > avoid without deprecations. See
> > > https://github.com/sympy/sympy/wiki/Deprecating-policy
> >
> > I think that if Theano itself is now unmaintained legacy software then
> > it's fine to say that if someone wants to use it with sympy they
> > should use an older version of sympy.
> >
> > > As an aside, one thing that has always annoyed me with Theano,
> > > especially when SymPy imports it for its tests, is that Theano does a
> > > lot of things at import time, such as running compilers to see if they
> > > work and printing many warnings (see
> > > https://github.com/sympy/sympy/pull/14747). I think it would be better
> > > to do these things at runtime, e.g., after the first function is
> > > called. I hope Aesara can improve this situation over Theano.
> >
> > This shows precisely that supporting something like Theano has a
> > nonzero cost even if that support is "deprecated". When migrating our
> > CI I had to work through many different projects that I do not know in
> > order to keep the test suite ticking over. Each of those makes general
> > project maintenance harder. I'm much happier about supporting a
> > maintained project that has a future and has maintainers willing to
> > help us provide support.
>
> These are fair points. It sounds like we should definitely not leave
> it as is. We should either deprecate it or remove it.
>
> The existing pull request only does a name change, suggesting there
> aren't very many differences between theano and aesara yet. So a
> deprecation wouldn't be that hard. If that changes in the future, it
> may be easier to just remove theanocode rather than trying to keep it
> around.
>
> >
> > I'm interested to hear from anyone using SymPy with Theano though (if
> > anyone on this particular mailing list is).
>
> Same here. I also am interested in more background on the fork. Theano
> itself was supposed to be "dead" a few years ago when the original
> developers stopped working on it, but then the pymc developers picked
> up maintenance. Could the same thing happen again?
>
> Also, I had heard that pymc was dropping theano in favor of tensorflow
> (do I remember this correctly?). Is this still planned, or has that
> changed to be aesara now?
>
> Aaron Meurer
>
> >
> >
> > Oscar
> >
> > --
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> .
>

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