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Re: Re: Coolest Mathematica trick you'll see this month

  • To: mathgroup at smc.vnet.net
  • Subject: [mg96860] Re: [mg96791] Re: Coolest Mathematica trick you'll see this month
  • From: Chris Pemberton <cjpembo at gmail.com>
  • Date: Thu, 26 Feb 2009 07:56:29 -0500 (EST)
  • References: <go0j6q$n2t$1@smc.vnet.net> <200902250902.EAA15595@smc.vnet.net>

ragfield wrote:
> On Feb 24, 4:46 am, Chris Pemberton <cjpe... at gmail.com> wrote:
>   
>> I use Linux on my machines and enjoy helping other Archlinux users in
>> the online forums.  A fellow Arch user was having issues with
>> Mathematica 7.  He was plotting a 3D parametric equation and
>> experiencing a sustained high processor load on this laptop; only
>> killing the kernel would allow the CPU to idle down.  He found that the
>> laptop's accelerometer kernel driver was eating nearly 30% of the CPU
>> time....  You'll just have to read the forum to see the rest!
>>
>> http://bbs.archlinux.org/viewtopic.php?id=65916
>>
>> Can any Windows or Mac users duplicate this?  Or is this a Linux-only
>> "feature"?  Or maybe this is well-known and I'm just late in finding ou=
>>     
> t?
>
> On Linux, Mathematica will treat devices at /dev/input/js0 through jsN
> as controllers.  As you discovered, apparently this laptop's
> accelerometer masquerades as a joystick. The high CPU usage is caused
> by the driver sending many updates to the device file descriptor,
> which Mathematica watches and does work whenever the values change.
>
> This can be disabled by adding the name of the controller (as returned
> by ControllerInformation[]) to the value list for the undocumented
> option "DisableControllers":
>
> SetOptions[$FrontEnd, DisableControllers -> Prepend
> [DisableControllers /. Options[$FrontEnd, DisableControllers], "DEVICE
> NAME HERE"]]
>
> -Rob
>
>
>   
Thanks for the info.  I'll pass it along.  That will be easier than 
unloading the accelerometer module.


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