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Kernel uses excessive CPU time *after* giving result.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg63861] Kernel uses excessive CPU time *after* giving result.
  • From: "Dave (from the UK)" <see-my-signature at southminster-branch-line.org.uk>
  • Date: Thu, 19 Jan 2006 03:43:24 -0500 (EST)
  • Reply-to: Jan-2006 at southminster-branch-line.org.uk
  • Sender: owner-wri-mathgroup at wolfram.com

I tried this:


In[1]:= N[1000000!]

                             5565708
Out[1]= 8.263931688331240 10


on Mathematica 5.2 on my quad processor Sun Ultra 80 (4 x 450 MHz, 
Solaris 10). Mathematica gives the result in about 20 seconds, but then 
the kernel goes on using 25% of my CPU time (there are 4 processors, so 
it is using one of them), *after* returning the result. I can then 
calculate something else, but the cpu usage stays pegged at 25% usage.

Here is the output from top a minute or two after the result has been 
returned.

load averages:  0.90,  0.75,  0.70 
08:11:26
115 processes: 111 sleeping, 4 on cpu
CPU states:     % idle,     % user,     % kernel,     % iowait,     % swap
Memory: 4096M real, 2473M free, 832M swap in use, 4412M swap free

    PID USERNAME LWP PRI NICE  SIZE   RES STATE    TIME    CPU COMMAND
  22543 drkirkby   3  30    0    0K    0K cpu/1    1:22 24.48% MathKernel
  22318 drkirkby   3  59    0  159M   90M sleep    6:45  1.54% mozilla-bin
    543 drkirkby   1  59    0  231M  129M cpu/2  160:48  1.23% Xsun
    798 drkirkby   2  59    0   92M   30M cpu/0   27:51  0.60% gnome-termin


Here is the output from prstat


sparrow /export/home/drkirkby % prstat
    PID USERNAME  SIZE   RSS STATE  PRI NICE      TIME  CPU PROCESS/NLWP
  22543 drkirkby   79M   34M cpu2    20    0   0:01:09  24% MathKernel/3
    543 drkirkby  231M  129M sleep   59    0   2:40:47 0.4% Xsun/1
    798 drkirkby   92M   30M sleep   59    0   0:27:50 0.4% gnome-terminal/2
  22318 drkirkby  159M   90M sleep   59    0   0:06:43 0.1% mozilla-bin/3


If I repeast this using the comment line 'math' rather than the GUI, the 
kernel's CPU usage drops back to zero after the result is returned.


-- 
Dave K

http://www.southminster-branch-line.org.uk/

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