Linas, But the truth values, attention values, etc. associated with an Atom are not immutable ...
so for instance, a MindAgent could add a new Version within a CompositeTruthValue object associated with an Atom ... ben On Tue, Sep 30, 2008 at 12:11 PM, Linas Vepstas <[EMAIL PROTECTED]>wrote: > Work on threading in opencog is on-hold because it seems > like a difficult problem. However, I was reading something recently, > which makes me think that perhaps a change of mindset could > convert this difficult problem into an "easy" one, by changing certain > core assumptions. > > I was reading about Clojure > http://wiki.jvmlangsummit.com/pdf/27_Hickey_clojure.pdf > > which is a LISP implementation on top of the JVM. One of the things > that Hickey talks about is multi-threading, and how "easy" it is, because > of a core design assumption he made: expressions would be immutable. > > This rang a bell: the hypergraphs in opencog are currently "immutable", > in the sense that, once I create something like > > SomeLink > SomeAtom "asdf" > OtherAtom "pqrs" > > I can not change the string values "asf" or "pqrs", I cannot add more > atoms to the link, I cannot remove the existing atoms from the link, > I cannot delete these atoms from the link, unless I also delete the link > first. So at least one key concept from clojure already exists in > opencog: immutablity. > > The key element that seems to be missing from opencog is > garbage collection. That is, although the incoming set for > "SomeAtom" will reveal that "SomeLink" is pointing at it, we > don't know who is pointing at SomeLink. Thus, there is no safe > way of deleting "SomeLink" if there is more than one "MindAgent" > (forget threads -- even when single threaded, if one MindAgent > is holding a pointer to SomeLink, its unsafe to delete it). > > If garbage collection was added, I think the multi-threading issues > just might go away (I haven't pondered deeply on this, though). > > I'm also thinking that adding something conservative, like the > Boehm garbage collector, might be pretty easy, almost trivially > so, as it might not require any big tear-up of the code ... or even > a small tear-up. The only interesting pieces would be to integrate > it properly with the ForgettingAgent, and &etc. -- and I guess with > the TLB and handles, since these act as pseudo-pointers. > > Anyone care to ponder this in greater detail? > > --linas > > _______________________________________________ > Mailing list: > https://launchpad.net/~opencog-dev<https://launchpad.net/%7Eopencog-dev> > Post to : [email protected] > Unsubscribe : > https://launchpad.net/~opencog-dev<https://launchpad.net/%7Eopencog-dev> > More help : https://help.launchpad.net/ListHelp > -- Ben Goertzel, PhD CEO, Novamente LLC and Biomind LLC Director of Research, SIAI [EMAIL PROTECTED] "Nothing will ever be attempted if all possible objections must be first overcome " - Dr Samuel Johnson
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