Re: [f-cpu] Winograd DCT on my seul.org account

[Juergen Goeritz <goeritz@oekomm.de>]

On Mon, 22 Apr 2002, Christophe wrote:
>> > Parallel execution is non-sense for uniprocessor and even multi-processor
>(each
>> > of them executes one sequential code). So I don't see the point.
>> i don't have the courage to prove the contrary tonight.
>> Maybe you will see the point if you do more application programming
>> and see that the reason why computers are so slow is because they are so
>> inherently serialised. A "parallel" langage has the purpose of showing
>> what is independent from what, it doesn't force you to use a parallel
>machine.
>> and multithread support if an old issue in the OS community. C does not
>> expose enough parallelism and requires explicit stuff which makes heavier.
>
>I'm speaking about parallel execution per instruction, not per thread
>(instructions in a thread are still serialized). So long as we get no real cpu
>able to execute parallel instructions, there is no real gain for anything for a
>true parallelism. Yes, a parallel language is okay to see what is independent
>(the good point) and shall be surely better than C but we will still have a lot
>of overhead due to the use of multithreading (stack space and switching for
>example). So if a CPU has power enough, we tend to use it more in serial way
>than parallel way since there is no real reason to think a multithreading would
>*ALWAYS* run better.

What do you mean by better? It may not be faster at all on
a single processor due to the extended overhead. But there
is one advantage compared to sequential programming. The
parallel threads could communicate with each other in new
ways if you think of each thread as a unique entity...

JG

*************************************************************
To unsubscribe, send an e-mail to majordomo@seul.org with
unsubscribe f-cpu       in the body. http://f-cpu.seul.org/