On Fri, Jan 24, 2020 at 6:19 PM Levente Uzonyi <leves at caesar.elte.hu> wrote:

> Hi Chris,
>
> On Fri, 24 Jan 2020, Chris Muller wrote:
>
> > Hi Jakob,
> >
> > Optimal execution performance can never be assured with #new, since the
> potential cost of under-allocation in various places is offset by the gains
> of not over-allocating in other places.
> >
> > Although it's impossible to tweak the default initial size in #new to
> optimize for performance, we can at least optimize for space, and also for
> clarity-of-usage.  #new, by nature, expresses a "lack of concern for
> optimization", so Squeak should at least provide compactness in that case.
> Places in the code that
> > need optimization will correctly express that by writing #new: with a
> larger pre-allocation.
> >
> > It's true that system level changes of any kind could result in the need
> for downstream changes but, in this case, it seems very unlikely.
>
> The way I understand it, Jakob says that your suggested change has a
> chance to slow down things just to save a few hundred kilobytes of memory.
>

But your suggested change is 100% *guaranteed* to slow things down, with no
space savings.

This avoids that particular slow down, while guarantee'ing to save space!
All for only a very *teency-weency chance* of other areas being minorly
affected (and, easily fixed if they are!).


> I don't think we would want to do that without measuring the effects of
> the change somehow.
>

Performance measuring is already part of every system that cares, right?
 :)
None of those systems are depending on any particular default initial size
for performance.  If they are, they should be fixed.


>
> Same applies to OrderedCollections.
>
> Following your reasoning, the optimal initial capacity for any dynamic
> collection created with #new should be 0, but that doesn't feel right...
>

Not 0, 3.  It's "reasoning", not extremism.  :)

3 would be a great default for OrderedCollection.  Ultra-minimal, but with
a purpose.   I mean, really, with 10, we have 92% of all instances wasting
space.

 - Chris

>
>
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