Recently we discussed (very briefly) how much one had to know about spaces to understand how to use Oz as a logic programming system. If one says 10,000 spaces instead of 10,000 threads, how does one explain (to someone who just wants to use it, not someone who wants to implement it or understand the implementation) what a space is, and how does one explain what happens after those 10,000 spaces are created? In other words, to explain Oz's abstract computational model, how does one explain what a space is and what part it plays in an Oz computation.
Another way of putting it is: what words go with Figure 9.2 on p 628 of CTM? The StrangeTwoDigit example on that page is explained in terms of depth-first-search. But do we really want to talk about Oz's computation model at that level? Of course, the order in which the results are presented is determined by something. (It is running on a deterministic single-processor computer after all.) But when one is just starting, we probably don't want to talk about that issue. The point is that SearchAll gives us all the results (in some order, which shouldn't matter to us--at least not now).
-- Russ
On 10/8/05, David Hopwood <[EMAIL PROTECTED]> wrote:
Russ Abbott wrote:
> This is about white being to the left of green, but I have to work up to it.
> (Since I not yet sure I know how to think about Oz's search protocols,
> perhaps the following is nonsense.)
> An hour ago (we have a Saturday class), I was explaining the palindrome
> project to my class as an introduction to Oz as a logic programming system.
> A piece of the code is
>
> N1 = 10*{Digit} + {Digit}
> N2 = 10*{Digit} + {Digit}
> X = N1 * N2
>
> where {Digit} generates all of the digits using choice. (This is from CTM
> chapter 9.) I said that the way to think about what's going on is that these
> two lines generate 10,000 threads, some of which get killed off later when X
> is found not to be a 4-digit palindrome. The ones that succeed produce
> results that are gathered together by SearchAll.
> (In Prolog one would talk about backtracking. I gather that in Oz one
> imagines them all running at once. Is that reasonable?)
Not really. When used in a search, this potentially creates up to 10000
*spaces*, but a space is not the same thing as a thread. How a search engine
uses threads is specific to each search engine.
--
David Hopwood <[EMAIL PROTECTED] >
_________________________________________________________________________________
mozart-users mailing list [email protected]
http://www.mozart-oz.org/mailman/listinfo/mozart-users
_________________________________________________________________________________ mozart-users mailing list [email protected] http://www.mozart-oz.org/mailman/listinfo/mozart-users
