Hi Dan, Though the sub-M FFTs are menaingless on 32 bit platforms. For Huygens we (Max and me) used 200,000 (decimal) FFTs on 64 bit platform to feel about a bit comfortable that phases are kept OK. Altough if we would push it to 1,000,000 it wold be 1-2 dB better. But cashing the memory was a killer, processing time wise.
Best regards and cheers, Sergei >>> Dan Werthimer <[email protected]> 06/24/08 9:24 PM >>> hi sergie and jouko, i'm not an expert at PS3 - my group tried to port a few programs - some were successful - those with a small memory footprint. it's a pretty painful programming environment. s...@home was a disaster (s...@home does 128K point FFT's), sony had three of their best engineers working on it for a long time and finally gave up. we've also played with GPU's. i'm not a big fan of specialized architectures, because they come and go, and you can't port software to the next generation (eg: array processors, cell, GPU's, bluegene torus interconnect, etc, are short lived). i like beowulf clusters with every node connected to every node through a switch and MPI, because they have/will be around for a long time and it's relatively easy to develop and port software through several generations of hardware. dan Jouko Ritakari wrote: > Hi all, > > On Tue, 24 Jun 2008, Sergei Pogrebenko wrote: > >> I also had some doscussions with Dan Werthimer about his FPGA plans >> (in a wake of uniboard project) and about Sony PS3. He and his team >> tried to re-write s...@home for PS3, but got it sadly running well below >> expectation. They contacted Sony/IBM compiler guys, but for 3 month >> no answer. > > We fortunately have the answer. > > Even vectorized and optimized code for PS3 often gets five to ten per > cent of the actual calculation capacity. > > It's a bit tricky to get the (about) 90% we got, we took Daniel > Hackenberg's matmul program and modified it. Daniel actually got 97% > efficiency, we didn't bother about the last seven per cent. It's less > expensive to buy more playstations. > >> Cross-pol feature is also of interest in a wake of new (ATA-kind) >> very broad band linear polarized feeds, so the conversion to circular >> polarization has to be done. For that the cross-pol complex spectrum >> should be calculated. >> >> Our results are very in-line with FPGA spectrometers, although they >> are much faster, it's difficult to get really hign resolution with them. > > > Well, the cell processors are the best you can have at the time, for > some of the tasks. FPGAs or display controllers are better for very > limited tasks, normal Intel-architecture or powerpc processors for very > big. > > If you have to do number-crunching the cell processor may be the best. > > And for you casper people, the PS3 control program may be even better > platform than PS3 Linux although much trickier. The folding-at-home > people are the ones to ask, they have the experience. > > > Best regards, > Jouko >
