opencog-dev team mailing list archive

["Joel Pitt" <joel.pitt@xxxxxxxxx>]

As far as I'm aware only the incoming set can change...

The outgoing set is fixed when you add a link to the AtomSpace/AtomTable.

J

On Tue, Sep 30, 2008 at 10:55 AM, Ben Goertzel <ben@xxxxxxxxxxxx> wrote:
>
> Also, of course, the ingoing or outgoing set of an Atom may be changed by a
> MindAgent ... why is this not a problem for concurrency?
>
> On Tue, Sep 30, 2008 at 1:51 PM, Linas Vepstas <linasvepstas@xxxxxxxxx>
> wrote:
>>
>> 2008/9/30 Ben Goertzel <ben@xxxxxxxxxxxx>:
>> >
>> > 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 ...
>>
>> Hmm. Well, if one thread is looking at a truth value while
>> another is setting it, then, in today's system, there would be
>> a crash (because the old value is deleted, and
>> Atom::getTruthValue() returns a reference).
>>
>> This could be solved by having AtomTruthValue() return
>> a copy, instead of a reference; but then one pays the
>> penalty of creating a copy, for each and every access.
>> (this is "copy-on-read").
>>
>> By contrast, in a garbage-collected system, the worst that
>> would happen is that someone is looking at an "old, stale"
>> truth value; as opposed to crashing.  By the principles
>> of concurrency, there's "no such thing" as an "old stale
>> value" in between synchronization primitives.
>>
>> --linas
>
>
>
> --
> Ben Goertzel, PhD
> CEO, Novamente LLC and Biomind LLC
> Director of Research, SIAI
> ben@xxxxxxxxxxxx
>
> "Nothing will ever be attempted if all possible objections must be first
> overcome "  - Dr Samuel Johnson
>
>
>
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