[EMAIL PROTECTED] wrote: > > > -------------- Original message -------------- > From: "Toon Knapen" <[EMAIL PROTECTED]> > > How come there is almost unanimous agreement in the > beowulf-community while the rest is almost unanimous convinced of > the opposite ? Are we just tapping ourselves on the back or is MP > not sufficiently dissiminated or ... ? > > Mmm ... I think the answer to this is that the rest of world > (non-HPC world) is in a time > warp. HPC went through its SMP-threads phase in the early-mid 1990s > with OpenMP, and then we needed more a more scalable approach > (MPI). Now that multi-core and multi-socket has brought parallelism > to the rest of the Universe, SMP-based parallelism has had a > resurgence ... this has also naturally caused some in HPC to revisit > the question as nodes have fattened. > > The allure of a programming model that is intuitive, expressive, > symbolically light-weight, > and provides a way to manage the latency variance across memory > partitions is irresistable. > > I kind of like the CAF extension to Fortran and the concept of > co-arrays. The co-array is > and array of identical normal arrays, but one per active > image/process. They are defined as such: > > real, dimension (N) [*] :: X, Y > > If the program is run on 8 cores/processors/images the * becomes 8. > 8, 1D arrays of size > N are created on each processor. In any references to the locale > component of the co-array > (the image on the processor referencing it), you can drop the []s > ... all other references (remote) > must include it. This is symbolically light, but reminds the > programmer of every costly non- > local reference with the presence of the []s in the assignment or > operation. There is much > more to it than that of course, but as the performance gap between > carefully constructed > MPI applications and CAF compiled code shrinks I can see the later > gaining some traction > for purely programming elegance related reasons. If you accept that > notion that most MPI > programs are written at a B- level in terms of efficiency then the > idea of gap closing may not > be so far fetched. CAF is supposed to be include in the Fortran > 2008 standard. > > rbw > > -- > > "Making predictions is hard, especially about the future." > > Niels Bohr > > -- > > Richard Walsh > Thrashing River Consulting-- > 5605 Alameda St. > Shoreview, MN 55126
But isn't CAF (and UPC, and Titanium) implicitly message passing for a Beowulf anyway? It's attractive because it simplifies the process and might be able to optimize communication, but underneath everything it's still message passing. -- Geoffrey D. Jacobs To have no errors would be life without meaning No struggle, no joy _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
