Performance comment (oddity with set.update())

[Torsten Bronger]

Hallöchen!

Robert Collins writes:

> On Tue, 2008-04-22 at 16:49 -0500, John Arbash Meinel wrote:
>
>> I was just debugging some performance issues, and I came across
>> something funny.
>> 
>> Specifically, calling 'set.update()' with a generator that
>> returns nothing is slower than building it into a list and then
>> updating.
>
> I think this is worth filing a python bug on, so that the python
> devs are aware of it.

I think the actual benefit of a generator is its reduced memory
consumption rather than higher speed.  Apparently, building a
generator has slightly higher fixed costs.  Getting the next element
is almost as costly for the generator as for the list (while
building it), so their performances behave asymptotically for many
iterations.

Tschö,
Torsten.

-- 
Torsten Bronger, aquisgrana, europa vetus
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