I found this most interesting in the context of how to go about parallelization: "...modern CPUs can execute hundreds of instructions in the time taken to fetch a single datum from memory." Even if this refers to low-level instructions, it gives an idea of the importance of minimizing data movement.
On Tue, Feb 16, 2010 at 1:35 PM, Don Guinn <[email protected]> wrote: > Thanks for the reference. Interesting. > > Looks like L1 cache is always private to the core. L2 and above may be > shared among all cores or not. The cache logic can get quite complex. Looks > like there is as many possibilities for performance optimization with cache > as with multiple cores. But probably inaccessible from C and is so > different > between models that it is probably unusable except in the most intensive > applications. And they are looking at doing memoization in cache. > > On Tue, Feb 16, 2010 at 10:45 AM, David Mitchell <[email protected] > >wrote: > > > On 2/16/2010 12:12, Don Guinn wrote: > > > On Mon, Feb 15, 2010 at 7:42 PM, bill lam<[email protected]> wrote: > > > > > >> . . . Given the large memory cache available in modern > > >> computer, it is better to just keep memory reference locality. The > > >> speed of transfer of data using socket would be slower than that > > >> within cache by at least 2 order of magnitude, just wild guess. . . . > > >> > > >> This touches on a question I have been wondering about. Is the cache > > shared > > > among multiple cores or does each one have its own cache? I would be > > > surprised if it is shared as that could result in a big performance hit > > if > > > there are lots of cores. If the cache is private to each core then > > somehow > > > the data has to be moved from one cache to another. Main memory? > > > ---------------------------------------------------------------------- > > > For information about J forums see http://www.jsoftware.com/forums.htm > > > > > > > http://en.wikipedia.org/wiki/L2_cache > > > > -- > > David Mitchell > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > -- Devon McCormick, CFA ^me^ at acm. org is my preferred e-mail ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
