On Mar 1, 1:32 pm, "Johan S. R. Nielsen" <j.s.r.niel...@mat.dtu.dk>
wrote:
> On Mar 1, 10:13 am, Robert Bradshaw <rober...@math.washington.edu>
> wrote:
>
> Nice! I weren't aware of this module. When you get a good idea,
> there's a good chance that someone else thought of it before ;-) I
> like the fact that one can dynamically hack into an object's
> namespace :-D However, lazy_import seems not to be used much (only 2-3
> places) currently in the Sage startup (or did I grep wrongly?). Was it
> never the intention or is it due to the overhead?
Yes, it is not used much. Ideally, the way of improving sage
startuptime would be:
1.- On first execution by a user, create a pickle of lazy_import of
the global names and save it in the .sage directory. This should not
be slower than current startup.
2.- Then, following executions of sage would only load that pickle
instead of reading hundreds of different files. This will translates
the delay from the start to the first call of the function. But note
that you will never call each global name so globally should be
faster...
3.- That pickle should be updated under certain conditions. By a
command, each time sage is updated etc.
Note that currently there are lazy_import(...) in the startup of sage,
but this command does not avoid disk access of the file, only
execution/compilation of the module to import. That is why it has
currently low impact.
> Also, I didn't proofread the entire lazy_import code, but the
> implementation seems to differ from my idea in a significant way: the
> LazyImport object keeps wrapping the imported objects. My thought was
> that the first time the imported object was accessed, it would replace
> itself with the original in the global namespace, and then forward the
> call. This way, there will be zero overhead in all later calls.
No, the lazy_import object keeps wrapping the original object, but
when accessing the lazy_import object it imports the real object in
the namespace. So, if the lazy_import has not been referenced by
another object then it will be collected as garbage. I do not have a
running sage right now, but if you experiment you will see that after
calling the object the lazy_import object disappears.
It should be something like:
{{{
sage: from sage.misc.lazy_import import lazy_import
sage: lazy_import('sage.rings.all', 'ZZ')
sage: a = ZZ
sage: type(ZZ)
<class 'sage.misc.lazy_import.LazyImport'>
sage: ZZ(4.0)
4
sage: type(ZZ)
<type 'sage.rings.integer_ring.IntegerRing_class'>
sage: type(a)
<class 'sage.misc.lazy_import.LazyImport'>
}}}
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