-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 6/24/2012 8:50 AM, Irit Katriel wrote: > > On 24 Jun 2012, at 03:47, Dave Abrahams wrote: >> >> Well, I think the hello world example is too simple to illustrate >> what this does, and the blog posting is TL;DR, but I skimmed it, >> and still didn't really have a clue. Have you looked at >> http://www.boost.org/doc/libs/1_49_0/doc/html/accumulators.html? >> It seems to have some overlap with the problems you're solving. >> > > I was not aware of accumulators, and I agree that there is some > overlap. As far as I can tell, the main differences are as follows. > Please correct me if I misunderstood anything. > > In the accumulators library, all the accumulators are invoked for > every update to the input. This is why the visitation order can be > determined at compile time.
That's correct. > I am building a dependency graph that is used at runtime to > determine which nodes need to be activated, so that inputs only > propagate through the part of the expression that may be affected. > Obviously I am imagining large expressions on many inputs, so that > this is worthwhile doing. Very interesting! So ... data flow? Or does this take inspiration from stream databases? > In addition, I am trying to achieve a more programming-like syntax > for complex expressions, by making the expression (rather than the > accumulator type) encode the dependencies between nodes. Since accumulators is solving a simpler problem, as DSL isn't needed there. For the more general problem you're solving, I think a DSL makes sense. > Example: you want to compute f(g(x),h(x)) over a stream. With > streamulus you define each of the functions f,g,h, and when you > subscribe the expression f(g(x),h(x)), and only then, f learns that > its inputs are the outputs of g and h. With accumulators you would > need to define the accumulator f_of_g_and_h(), make it depend on g > and h, give it a tag, and then add it to the accumulators list. > > Similarly, with streamulus you can define your function f, and then > use it multiple times within the same expression: sqrt(sqrt(x)). > This will build a graph with three nodes : (x--> sqrt-->sqrt) where > x is an input node and the two sqrt's don't need to know or care > about each other because a different instance was constructed for > each node. > > I'm sorry about the too-long blog post.. It mostly deals with the > bad things that can happen if you DIY your stream computations. You > can skip most of it and just look at the definition of the sample > application in the beginning, and then the streamulus solution in > the end. Looks pretty interesting. Thanks for sharing. - -- Eric Niebler BoostPro Computing http://www.boostpro.com -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJP54V6AAoJEAeJsEDfjLbXhKwH/1khe8DP9wSY3rc6KrIfPzux MBSPyiz2vOqT5C/I1pIVXHo71dzNttcLp0NfLTII/++T5Df9MEiE3wfufBBWKDjv elI/2QCgYzEm8IeGUqN3oRz9I0XprsOfWqxsfJs6TglL+JiNlHENBbaH8GGkPI8s Nn1ntI+SWFzhqjaBB9gYyosDYT9f2bRYGQAO0/Ov/+hhjX7tSPc/pET2MOpn0L5p NsyOJv7bqPAICn61yT0O+XJpDBGLeGpqFumsJryMJoxcT/sv1Lvlh2FAIhfrjet6 TAB0lfRKI92O4Bw+kE+lOLRI1TMTKBr8ig+Ykodm0myNLItJRWrV2/9Q2nXTzco= =Ok3v -----END PGP SIGNATURE----- _______________________________________________ proto mailing list proto@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/proto
