Re: asynchronous python code blocks in org-mode

[John Kitchin <jkitchin@andrew.cmu.edu>]

Tom writes:

> On Mon, Nov 30, 2015 at 1:06 PM, John Kitchin <jkitchin@andrew.cmu.edu>
> wrote:
>
>> I have not thought about sessions and asynchronous execution. It would
>> mean a queue and a different way to pass code to the process, which I
>> have not thought through yet. What to do when there are dependencies for
>> example,...
>>
>
> A good way of converting synchronous into asynchronous code is to use
> futures/promises. Usually, that's done via data structures, but within
> Emacs buffers, it could be done via text strings.
>
> How might that work? org-babel-execute:python could wait for, say, 0.1 sec
> for an immediate result. If the computation doesn't finish within that
> time, it returns a "future", a magic string like
> "org_mode_future_result(1234) ###MAGIC###". This would then get inserted as
> output into the org-mode buffer. Later, when the actual result becomes
> available from the subprocess, that invokes a callback on the org-python
> mode buffer and replaces tihs magic string with the actual result, and
> dequeues and executes the next command if necessary.

This is basically what happens now, I insert a uuid that gets replaced by
a callback function.  A session is doable I think as you describe. Its
not a high-priority for me though. I feel like it would eventually be
necessary to have some queue management functions, e.g. what to do if
you run a block twice? or want to cancel a run, etc... How to make sure
dependencies are correct, e.g. you can start a second block before the
first block finishes, but it is queued. etc...

> (Picking a Python-parseable expression would even allow futures to be used
> in some other Python computations as if it were an actual value.)
>
> I think that would allow much of the current API to remain in place.
> Obviously, some things simply can't work. For example,
> org-babel-reassemble-table expects an actual result, not a future; such
> post-processing would have to move to a hook function, which probably would
> be cleaner anyway.
>
> Tom

--
Professor John Kitchin
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu