[IPython-dev] should we make nodb the default hub backend?

Fernando Perez fperez.net at gmail.com
Mon Jun 11 22:52:13 EDT 2012

Hey guys,

I'm wondering if we shouldn't make nodb the default... The new cell
magics and the ability to combiine cython with parallel stuff make it
so blindingly easy to parallelize existing codes (for certain
patterns, of course!) that I bet people are *quickly* going to run
into the problems with memory introduced by the persistent backends.
I was just now parallelizing some Gibbs sampling code in Cython
written by Chris Fonnesbeck for a panel at the R conference later this
week, and all of a sudden noticed my machine grind to a halt.  I had
only run the code a few times, and I was overwriting the same
variables over and over, so I wasn't really thinking I'd be in memory
trouble, but it was the hub's persistence that bit me.

The DB backends are really useful only in more advanced circumstances,
so I'm thinking that perhaps they should be activated knowingly by
users who need their features, leaving the 'naive' patterns to behave
a bit better.  What I'm worried is that right now, a fairly natural
use pattern degrades badly and somewhat mysteriously (unless you
really know what's under the hood).



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