Stefan Israelsson Tampe <stefan.ita...@gmail.com> skribis: > On Tue, Oct 29, 2013 at 1:34 PM, Ludovic Courtès <l...@gnu.org> wrote: > >> Hi, Stefan, >> >> Stefan Israelsson Tampe <stefan.ita...@gmail.com> skribis: >> >> > I did some tests witha C-based vhash implementation, it's possible to >> > increse the speed by 30x compared to current vlist imlpementation in >> > guile. It would be possible to get this speed today if one implemented >> > vhash-assoc as a VM op. Anyway using the source as a standard lib will >> > get you about 10x speed increase. >> >> As we discussed, I don’t really like the idea of implementing that much >> in C. >> > My neither, but it is good to see that in cache friendly cases we can > improve the situation 30x. Gives us a goal to strive for. Also the main > intention is to use vashses for guile-log. For this we can note.
OK. [...] >> > Another pressing need is that vhashes are not thread safe, >> >> Section 2.8 of Bagwell’s paper proposes a simple solution. All that is >> missing AFAICS is an atomic test-and-set VM op to implement it (which >> may also be useful in other places.) >> >> What do you think of this approach? > > > For vlists it's probably a good idea, I don't know if it's enough for > vhashes though. Oooh, right, sorry for overlooking that. > Maybe you need a mutex. But lock overhead will be significant Surely, especially if it’s a fat mutex. Hmm hmm. Of course that could be an argument for doing some C (primitives, not VM ops), but looking at ‘%vhash-assoc’, that would clearly mean reimplementing pretty much all of the vlist + vhash in C, which sucks. I wonder if there’s some other data structure with similar properties that doesn’t have the thread-safety issue. Maybe Ian has an idea? The weight-balanced trees in MIT/GNU Scheme look interesting: http://www.gnu.org/software/mit-scheme/documentation/mit-scheme-ref/Weight_002dBalanced-Trees.html Thoughts? Thanks, Ludo’.
