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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg96791] Re: Coolest Mathematica trick you'll see this month guaranteed
  • From: ragfield <ragfield at gmail.com>
  • Date: Wed, 25 Feb 2009 04:02:17 -0500 (EST)
  • References: <go0j6q$n2t$1@smc.vnet.net>

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


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