4 ms·

Yes, this is a trope amongst the amateur fan base of the Raspberry Pi and it is familiar in many other avocations. "I know my hobby X is not good enough, but i

Yes, this is a trope amongst the amateur fan base of the Raspberry Pi and it is familiar in many other avocations. "I know my hobby X is not good enough, but if I got enough of them, it might be way better than things actually designed to do X!" When it was first proposed to me about a year or two ago, to massively connect RPis, I quickly did the math and showed a simple top-of-the-line graphics card ( I did the numbers for a Radeon 7970 ) outperformed RPis at a factor of something like 10 to 1 in price/GFlops. That's without even considering interconnections. I know Jacques Mattheij is some kind of folkhero here on HN, so I'll tread lightly, but I find this weak as it's years overdue and comes complete with a non-committal call to someone else doing the action- not a value in this community. He implies his time is worth more than other people's: "Doing this will be [...] well worth it." "If anybody builds this let me know"

rwmj 13y ago
Those who haven't read Kumar, Grama, Gupta and Karpis[1], are doomed to rediscover it, painfully. [1] http://www.amazon.com/Introduction-Parallel-Computing-Analysis-Algorithms/dp/0805331700 http://www.amazon.com/Introduction-Parallel-Computing-Analys...
- chillingeffect 13y ago
  Do you happen to know if there's a particular term or metric that describes the cost of the overhead of interconnecting elements?
  - rwmj 13y ago
    The book (above) has a comprehensive series of equations you can use to measure the cost of interconnections in parallel algorithms. I can tell you I did an MSc-level course in this, and it is very complex, one of the hardest courses I did on what was a very difficult MSc. Edit: But basically your comment about interconnecting RPis with ethernet is completely true. It's a huge waste of time.
jacquesm 13y ago
Radeons and other GPU based solutions are extremely effective for some classes of problems but definitely not for all of them and they typically scale extremely bad if the problem does not map well onto the underlying architecture. I've been doing quite a bit of work using GPU's for problems that they are well suited to and the performance is extremely impressive. But as soon as you need more decoupling for whatever reason between the individual instruction streams they are not a very effective solution. The communications overhead made by the GP is a good point and I'll definitely look into that, the xmos stuff linked elsewhere in this thread is very interesting as well. Whether or not I'm a folk hero is up for debate, but feel free to speak as though you would to anybody else, I have 0 privileges here and would find it strange if people were to act differently because of my visibility. When I'm wrong I'm wrong. And as to your last point: I simply don't have the skills to route the board required, that's why this is a blog post without schematics or board layouts. That's not because 'my time is worth more than other people's', see my other projects as proof to the contrary. As for this being years overdue, the RasPi compute module has been out for only a few weeks.

rwmj 13y ago

Those who haven't read Kumar, Grama, Gupta and Karpis[1], are doomed to rediscover it, painfully. [1] http://www.amazon.com/Introduction-Parallel-Computing-Analysis-Algorithms/dp/0805331700 http://www.amazon.com/Introduction-Parallel-Computing-Analys...

chillingeffect 13y ago
Do you happen to know if there's a particular term or metric that describes the cost of the overhead of interconnecting elements?
- rwmj 13y ago
  The book (above) has a comprehensive series of equations you can use to measure the cost of interconnections in parallel algorithms. I can tell you I did an MSc-level course in this, and it is very complex, one of the hardest courses I did on what was a very difficult MSc. Edit: But basically your comment about interconnecting RPis with ethernet is completely true. It's a huge waste of time.

jacquesm 13y ago

Radeons and other GPU based solutions are extremely effective for some classes of problems but definitely not for all of them and they typically scale extremely bad if the problem does not map well onto the underlying architecture. I've been doing quite a bit of work using GPU's for problems that they are well suited to and the performance is extremely impressive. But as soon as you need more decoupling for whatever reason between the individual instruction streams they are not a very effective solution. The communications overhead made by the GP is a good point and I'll definitely look into that, the xmos stuff linked elsewhere in this thread is very interesting as well. Whether or not I'm a folk hero is up for debate, but feel free to speak as though you would to anybody else, I have 0 privileges here and would find it strange if people were to act differently because of my visibility. When I'm wrong I'm wrong. And as to your last point: I simply don't have the skills to route the board required, that's why this is a blog post without schematics or board layouts. That's not because 'my time is worth more than other people's', see my other projects as proof to the contrary. As for this being years overdue, the RasPi compute module has been out for only a few weeks.