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MathGroup Archive 2006

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Re: Re: Illusory Multicore Support in 5.2?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg66056] Re: [mg66046] Re: Illusory Multicore Support in 5.2?
  • From: George Woodrow III <georgevw3 at mac.com>
  • Date: Fri, 28 Apr 2006 06:32:32 -0400 (EDT)
  • References: <200604260838.EAA02742@smc.vnet.net> <e2pp8k$su2$1@smc.vnet.net> <e2q0o1$1t7$1@smc.vnet.net> <200604270935.FAA03741@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Using Mathematica 5.2.2 on OS X 10.4.6 PowerMac QuadCore. I haev 8  
Gbytes RAM

I ran Activity monitor to see the CPU usage graphically.

I executed the following in 1 cell so that all the computations would  
be passed to the kernel at the same time:

N[Ï?, 100000000]; // Timing
N[ϵ, 100000000]; // Timing
N[Sqrt[2], 100000000]; // Timing

(doing just 1000000 places returned too fast -- pi in 3.4 seconds and  
the others much faster. I asked for 100 times the decimal places so  
the program would run for a while.)

I would expect one thread per computation -- they are independent.  
Instead, I get 100% of one CPU all the time. The CPU switches from  
time to time -- probably the OS resolving usage/heat issues.

The Activity monitor reposts MathKernel using 3 threads and 99.9% of  
the CPU -- the max is 400%. I can get more than 200% of CPU usage  
running iTunes's visualliser with all the options cranked up, or Sims  
2. There appears to be no problem with the OS distributing a multi- 
threaded app among the processors.

The good news is that there is no slowdown from the rest of my apps:  
the OS distributes the usage among running apps very well. the Bad  
News is that Mathematica seems to be using only one CPU at a time.

george

On Apr 27, 2006, at 5:35 AM, Chris Chiasson wrote:

> Do the posters in this thread happen to be running a 32 bit version of
> Mathematica?
>


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