From: Linus Torvalds Date: Thu, 07 Sep 2006 00:45:01 GMT Subject: Re: A look at some alternative PACK file encodings Message-ID: In-Reply-To: <44FF6586.8080206@gmail.com> On Wed, 6 Sep 2006, A Large Angry SCM wrote: > > > Btw, that "keeping the ordering it had" part I'm not convinced we actually > > enforce. That would depend on the sort algorithm used by "qsort()", I > > think. So there might be room for improvement there in order to keep > > things in recency order. > > qsort() is not stable. Well, quicksort isn't, but a lot of systems don't actually use quicksort to implement qsort() - despite the name. I think, for example, that glibc uses a merge-sort when there are lots of entries (to avoid any potential bad behaviour with quicksort), and that should be stable. But I didn't actually check.. In fact, I didn't even think of this issue originally, but it might actually be worthwhile doing our own sort, exactly because we'll otherwise have different systems generating different pack-files due to issues like this. So even if we don't actually _care_ whether the sorting is stable or not, we might well care that we always get the same results, regardless of what C library we have. > > Is there any way to get zlib to just generate a suggested dictionary from > > a given set of input? > > The docs suggest "no". Oh, well. Linus