[R-SIG-Mac] Multi-thread R processes performance on 8-core Mac-Pro

[Marra, David]

> The Intel's SMP design is poor compared to its competitors (not just  
> the MoBo, the CPUs as well), that is a well known fact, but I  
> wouldn't be so sure that it is what hits you. Can you try to run some  
> some big BLAS  operations like for example:

> set.seed(1)
> a<-matrix(rnorm(4000000),2000)
> b<-matrix(rnorm(4000000),2000)
system.time(for (i in 1:20) a%*%b)

> This takes ca 14.2s on a 2.66 quad Mac Pro (46.5s user time). I  
> wonder what the 8-core does with this. If you can't feed all 8 cores  
> then I'd say it's likely a bandwidth issue ...

> Cheers,
> S


Simon, the BLAS operation above completes in 9.0 seconds on the 3.0 8-core Mac Pro. About 37% faster than you 2.66 quad, which closely matches the performance gain barefeats.com found in a recent multi-tasking test. On this test, the cores maxed out at about 70%. The remaining 30% probably gets wasted due to the I/O issue.

See: April 19th, 2007 -- MULTI-PROCESSING: 8 Core versus 4 Core Mac Pro (or "What happens when four CPU hungry apps fight for all available cores?")
http://www.barefeats.com/octopro3.html

Best,
David