From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ward Deng Date: Sun, 26 Jul 1998 04:00:05 +0000 Subject: Re: Ultra AXmp Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ultralinux@vger.kernel.org > > Hardly worth investing time or $$$ in a communication network when you're > only spending 15% of the time there! If the NPB aren't representative, > well, that's another problem ... This is one side of the view. However, because of the heterogeniety of the memory allocation, you simply leave the burden to programmers. There are some algorithms are invented, which is good news. Instead of letting programmers learn new computer architectures one by one before they know how to write their programs :-). I just try to remind people that the current status of Beowulf type system is not panacea for the majority of computational challenges. This is why CM-5 users and Cray users are more productive than IBM SP2 users. We still have long way to go. Also most bandwidth tolerent algorithms have not been invented (it also take time and $$$) if ever in computations a little bit more sophisticated than Ax=b or FFT problems. Remember some algorithms require users to make the dimension of their matrix A dividable by the number of processors ;-(. > > I'm more and more convinced that inter-processor communication is no > longer a first order issue. Focusing on memory system efficiency > (effective use of the cache and memory BW) will get you much more bang for > your buck. Even in the parallel case, I would spend money on huge L2 > caches and memory bandwidth over processor interconnect. > I believe someone feel that way but I have not convinced yet since starting working on the first generation of IBM SP system. I totally agree that high system throughput and SMP is very important and welcome. However, lower lantency inter-processor communication is also important. It is not that binary. > My humble $0.02 worth... > Me too. --ward