Author: Dann Corbit
Date: 13:20:25 09/26/01
Go up one level in this thread
On September 26, 2001 at 15:18:37, Robert Hyatt wrote: [snip] >The question is, however, is "how does it do on 2 processors compared to the >best sort algorithm on 1?" or "how does it do on 1 processor compared to the >best sort algorithm on 1?" > >And none of this really has anything to do with chess. Alpha/Beta is a well- >defined algorithm. There is no "flexibility" in how it is done, because it is >a simple mathematical expression of a search space (the minimum search space) >that must be traversed to produce a result. Nobody claims that someone might >not one day develop a better algorithm to do searches in parallel. Something >not based on alpha/beta at all. But right now we are all using the _same_ >basic algorithm, whether serially or in parallel. And _that_ makes super-linear >impossible to accept on a regular basis. It just won't happen. Maybe Vincent has made some improvements. There are some obvious things that come to mind. Consider a shared memory alpha and beta... The search could be modified mid-stream if there is a fail-low or fail-high for all the processors instead of discovering the fact only after you have completed your search. I also wonder why a program with a shared hash table does not do better than a single CPU, since both CPU's are adding data to the hash table and therefore both programs can find answers. Surely there are transpositions from different points of the search. Of course, a twice as fast CPU would accomplish the same thing, but we don't have many 2GHz CPU's yet. Or consider... While CPU #1 is searching the root, CPU #2 is on the pm (whatever that is). This would benefit a lot more if we have a lot of CPU's who can split the job of searching the root, and another set of one or more CPU's which can search the ponder move. Often, by advancing to the solution move, results can be found much faster than by searching the root -- even for ten times as long. In other words, we are assuming that Vincent has not made an innovation. Now, all three of the ideas I put forth might be stupid. But maybe Vincent has come up with a real stunner.
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