Indeed we were discussing this in the IRC,
Actually it is interesting to note that the continuos function written
as comment in newCapacity
double mult2 = 1.0 + (size / log10(pow(newcap * 2.0,2.0)));
does *not* have that behaviour.
It seems to me that it is generally much better to work on the total
memory rather than on the number of elements.
I would use something like
long mult = 100 + 200L / log2plus2(newcap)
and round up
newext = cast(size_t)((newcap * mult) / 100);
newext += size-(newext % size);
This is what I am adding in tango.
thinking more about this, given that one starts at pagesize ~4024,
log2=12 this might be too conservative, I will test a little bit more...
One could add something that further favors large sizes, but I miss the
rationale behind that, I would rather expect that one typically
concatenates strings (size=1..4) and so there is more to gain by making
that faster.
I can also understand if someone wants to use only the number of
elements (rather than the total size), but what was implemented wasn't
that either.
maybe the number of elements is really the correct thing to do...
If someone has some insight, or good benchmarks to choose a better
function it would be welcome.
Fawzi
