[IPython-dev] Implementing inline images in a kernel

[Brian Granger]

On Tue, Jan 28, 2014 at 8:30 PM, Gabriel Becker <gmbecker at ucdavis.edu> wrote:
> Is there any reason a kernel (or metakernel if you want to call it something
> else) cannot know how to send code to more than one evaluator? It seems to
> me that the magics themselves are proof that this could easily be achieved
> in (I)Python. It seems like it should be pretty straightforward to push that
> dispatch up from the "now evaluate our python code" step into a new
> intermediary "check the language and evaluate accordingly" step.

With a little bit of thinking...

To do a sucky job it wouldn't be hard. Do just as you say, make
everything work through an in process blocking API passing simple data
structures from the evaluators to the "routing kernel"

To do a good job and have everything (tab completion, tooltips, async
output, widgets, etc.) work is extremely difficult and would require
very careful asynchronous routing logic using all of our zeromq
sockets from the backend "evaluators" to the main "routing kernel".
Not to mention that if all of these evaluators are running in process,
they will actively block one another. What happens if your user tab
completely in a logo cell while a VisualBasic one is running? How do
you route that? What happens if your user drags a slider in a Java
backed IPython Widget? How do you route that? What if the entire
backend is blocked by code running in another evaluator? What if some
of these objects are shared in different evaluators? Which one gets to
handle output at any given moment in time?

People tend of think of the messaging in IPython as being simple
request/reply. Browser sends code to the kernel, kernel replies with
output. Nothing can be further from that. Message can be sent
bidirectionally at any moment in time by either party. The
widgets/comm stuff use that all over the place.

Summary: if you are going to want a kernel with all the features that
IPython offers (not just blocking code execution) don't try to build
this type of "routing kernel" - build kernels that run code in one
language.

> Signalling the language of a particular code cell to the user could be done
> with a small icon or other indicator in the page.

Yes, that is perhaps the only trivial part...

Cheers,

Brian

> I had toyed with the idea of building such a metakernel myself (why build an
> R kernel when I could build a kernel for truly multilanguage notebooks) but
> I never found the time.
>
> ~G
>
>
> On Tue, Jan 28, 2014 at 6:17 PM, Brian Granger <ellisonbg at gmail.com> wrote:
>>
>> Jason, to illustrate:
>>
>> Idée intéressante
>>
>> Но я думаю, что есть некоторые проблемы
>>
>> Ben kullanıcılar için çok kafa karıştırıcı olacağını düşünüyorum
>>
>> ほとんどの人は、一度に1つの言語を追跡することができます
>>
>> מספר שפות היו שמות עומס קוגניטיבי משמעותי על משתמשים עם יתרון ברור קטן
>>
>> French, Russian, Turkish, Japanese, Hebrew. Have fun translating :)
>>
>> On Tue, Jan 28, 2014 at 6:10 PM, Brian Granger <ellisonbg at gmail.com>
>> wrote:
>> >> What if we supported different kernels on a per-cell basis?  Then it
>> >> would be similar to the %% magics.  There could be a number of kernels
>> >> associated with a notebook, and the metadata on a cell would tell where
>> >> to send the code and get output from?
>> >
>> > User's heads will already explode with the ability to change kernels
>> > on the fly for an entire notebook. Allowing that for individual cells
>> > would lead to a further explosion of UI complexity and cognitive load.
>> > Obviously, anyone is free to build such a beast, but I can't imagine
>> > that ever being within scope for IPython itself.
>> >
>> > Cheers,
>> >
>> > Brian
>> >
>> >> Thanks,
>> >>
>> >> Jason
>> >>
>> >> _______________________________________________
>> >> IPython-dev mailing list
>> >> IPython-dev at scipy.org
>> >> http://mail.scipy.org/mailman/listinfo/ipython-dev
>> >
>> >
>> >
>> > --
>> > Brian E. Granger
>> > Cal Poly State University, San Luis Obispo
>> > bgranger at calpoly.edu and ellisonbg at gmail.com
>>
>>
>>
>> --
>> Brian E. Granger
>> Cal Poly State University, San Luis Obispo
>> bgranger at calpoly.edu and ellisonbg at gmail.com
>> _______________________________________________
>> IPython-dev mailing list
>> IPython-dev at scipy.org
>> http://mail.scipy.org/mailman/listinfo/ipython-dev
>
>
>
>
> --
> Gabriel Becker
> Graduate Student
> Statistics Department
> University of California, Davis
>
> _______________________________________________
> IPython-dev mailing list
> IPython-dev at scipy.org
> http://mail.scipy.org/mailman/listinfo/ipython-dev
>



-- 
Brian E. Granger
Cal Poly State University, San Luis Obispo
bgranger at calpoly.edu and ellisonbg at gmail.com