Newsgroup: it.comp.console.playstation
Titolo: Mr. Bean conferma, PS3 potentissima

http://www.umassd.edu/engineering/phy/people/faculty/gkhanna/welcome.cfm
http://www.gamesnation.it/news/895/un-mistero-della-scienza-risolto-grazie-ad-un-gruppo-di-ps3.html
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Un mistero della scienza risolto grazie ad un gruppo di PS3
di Demetrio Porcino
Un mistero della scienza risolto grazie ad un gruppo di PS3
Utilizzando la potenza di calcolo combinata di sedici PlayStation 3,
alcuni scienziati dell’Università di Alabama e del Massachusetts hanno
svolto una difficile ricerca nel campo dell’astrofisica. I ricercatori
hanno spiegato che non avrebbero potuto pagarsi il supercomputer
necessario per eseguire la ricerca, e che la combinazione di più PS3 è
stata perfetta per sostituirlo. È probabilmente la prima volta che questo
tipo di ricerca è condotta esclusivamente con un gruppo di PS3 unite allo
scopo di ottenere la potenza di calcolo di un supercomputer e realizzare
così delle speciali simulazioni.
Il grande vantaggio di quest’insieme di 16 PS3 (chiamato The PS3 Gravity
Grid) è stato il risparmio di denaro, come spiega chiaramente il Dr. Lior
Burko, uno dei partecipanti al progetto: "Se avessimo affittato un
supercomputer, ci sarebbe costato 5000 dollari per ogni simulazione. Ma
per un progetto di questo tipo abbiamo bisogno di fare molte decine di
prove con parametri diversi. E quindi sarebbe stata necessaria una gran
quantità di denaro. Così abbiamo deciso di assemblare questo gruppo di PS3
spendendo circa 6000 dollari, e quel costo ha coperto tutte le simulazioni
necessarie".
Il Professor Gaurav Khanna, che ha materialmente assemblato le PS3, ha
aggiunto: "I fondi per la scienza si sono drasticamente ridotti in
occasione degli ultimi dieci anni, e così siamo contenti di aver trovato
un modo più economico per fare ricerca". Per condividere questa piccola
scoperta con altri scienziati che avessero un uguale bisogno di
risparmiare, il gruppo di ricerca ha lanciato un sito Internet, al cui
interno è stato inserito il metodo di "parallelismo" delle PS3, spiegato
passo per passo e reso così alla portata di tutti.
Conclude il professor Khanna: "L’insieme delle PS3 era particolarmente
adatto alla natura del nostro progetto (che ricercava la velocità alla
quale un buco nero vibrante ferma le sue vibrazioni), che richiede un
grande numero di calcoli matematici ma sollecita poco la memoria RAM. Non
tutti i tipi di ricerca sono gestibili con questo sistema, ma per noi era
ottimale".
Praticamente il primo indiano che si affaccia su una PS3 sfrutta meglio le
PS3 di tanti programmatori la in giro... andiamo bene.
-- 
.PYT..
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http://gravity.phy.umassd.edu/ps3.html
This section is dedicated to the ongoing research projects of our group that
involve supercomputing in Physics.
The Sony PlayStation 3 has a number of unique features that make it
particularly suited for scientific computation. First, the PS3 is an open
platform, which essentially means that one can run a different system
software on it, for example PowerPC Linux. Next, it has a revolutionary
processor called the Cell processor which was developed by Sony, IBM and
Toshiba. This processor has a main CPU (called the PPU) and several (six for
the PS3) special compute engines (called SPUs) available for raw
computation. Moreover, each SPU performs vector operations, which implies
that they can compute on multiple data, in a single step. Finally, its
incredibly low cost make it very attractive as a scientific computing node
i.e. part of a cluster. In fact, its highly plausible that the raw computing
power per dollar that the PS3 offers, is significantly higher than anything
else on the market today!
Thanks to a very generous, partial donation by Sony, we have a sixteen PS3
cluster in our department, which we call PS3 Gravity Grid. Check out some
pictures of the cluster here: 1) the PS3's arrive; 2) the rack arrives; 3)
front view of the cluster; 4) side view of the cluster.
We are using "stock" PS3s for this cluster, with no hardware modifications.
They are networked together using an inexpensive netgear gigabit switch. For
Linux installation, there are several guides available on the internet. For
YDL Linux, consider using the guide by Terrasoft Solutions. For Fedora 8, I
found this guide particularly useful. For deploying a parallel job on this
cluster, we use a code that implements a standard domain decomposition
approach, based on message-passing (MPI). There are more details available
on our code below. For compiling, we use GCC and also IBM's XL compilers for
the Cell, that are available as part of IBM's Cell SDK. The MPI distribution
that we are using is the recently released, OpenMPI distribution for PowerPC
Linux.
Projects
  a.. Binary Black Hole Coalescence using Perturbation Theory (GK)
  This project broadly deals with estimating properties of the gravitational
waves produced by the merger of two black holes. Gravitational waves are
"ripples" in space-time that travel at the speed of light. These were
theoretically predicted by Einstein's general relativity, but have never
been directly observed. Currently, there is an extensive search being
performed for these waves by the newly constructed NSF LIGO laboratory and
various other such observatories in Europe and Asia. The ESA and NASA also
have a mission planned in the near future - the LISA mission - that will
also be attempting to detect these waves. To learn more about these waves
and the recent attempts to observe them, please visit the LISA mission
website.
  The evolution code for the extreme-mass-ratio limit of this problem
(referred to as EMRI) is essentially like an inhomogeneous wave-equation
solver which includes a very complicated source-term. The source-term
describes how the smaller black hole (or star) affects the space-time of the
larger one. Because of the computational complexity of the source-term, it
is often the most numerically intensive part of the whole evolution. On the
PS3's Cell processor, it is precisely this part of the computation that is
farmed out to six SPUs. This approach essentially eliminates the entire time
spent on the source computation and yields a speed up of over a factor of
five over a PPU-only computation. It should be noted that the context of
this computation is double-precision floating point operations. In
single-precision, the speed-up is significantly higher.
  Overall, a single PS3 performs better than the highest-end desktops
available and compares to as many as 25 nodes of an IBM Blue Gene
supercomputer. And there is still tremendous scope left for extracting more
performance through further optimization. More on that soon.
  Furthermore, we distribute the entire computational domain across the
sixteen PS3s using MPI (message passing) parallelization. This enables the
entire cluster to run together in parallel, working on the computation in an
efficient way. Each PS3 works on its part of the domain and communicates the
appropriate data to the others, as needed.
  a.. HPL - Standard supercomputer cluster benchmark (GK)
  This project is about performing a standard LINPACK cluster benchmark on
our sixteen (16) PS3 cluster. This is the benchmark that is used by the
top500.org
 site that lists the most powerful supercomputers in the world. We
worked with IBM to port their Cell blade benchmark code to our PS3 cluster.
The results? The PS3 Gravity Grid generates a total performance of 40 GFLOPS
(40 billion calculations per second). It should be noted that this benchmark
was run in double-precision and because of the limited RAM on each PS3 we
were only able to fit a matrix of size 10K on the entire cluster. The larger
the problem size, the better the PS3/Cell's efficiency, therefore these
testing conditions were far from optimal, unfortunately. We expect to be
able to get much much better performance from the cluster if we had
significantly more RAM available! Even with the 40 GFLOPS, our PS3 cluster
is very competitive (in terms of performance-per-dollar) with the low-cost
compute clusters out there. And if one could take advantage of doing some of
the computation in single-precision, the performance would jump several
fold -- likely touch one-half a TFLOPS (half a trillion calculations a
second). The benchmark code with Cell specific patches is available here:
HPL.