Re: Coolest Mathematica trick you'll see this month

• To: mathgroup at smc.vnet.net
• Subject: [mg96792] Re: [mg96769] Coolest Mathematica trick you'll see this month
• From: DrMajorBob <btreat1 at austin.rr.com>
• Date: Wed, 25 Feb 2009 04:02:28 -0500 (EST)
• References: <200902241047.FAA23647@smc.vnet.net>

```I'd write it this way:

Clear[doubleBallMap, c2r4, spinKet]
doubleBallMap[v : {w_, x_, y_, z_}] := {y, z, Sign[x]*(w + 1)/2}/
Sqrt[v.v];
c2r4[{w_, x_}] := {Re[w], Im[w], Re[x], Im[x]};
spinKet[\[Beta]_, t_] := {Sin[\[Beta]/2] Exp[-I 2 \[Pi] t],
Cos[\[Beta]/2] Exp[I 2 \[Pi] t]};
ParametricPlot3D[
Map[(doubleBallMap[c2r4[spinKet[#, t]]]) &,
Range[0, \[Pi], \[Pi]/16]], {t, 0, 2 \[Pi]}]

(All those Extract-ions are obtuse and distracting.)

Drawing the 3D graphic initially is slow, but I don't get any problems
when rotating the image. (That's what the post complained about.)

I doubt most of us have "accelerometer" drivers, so I can't help you with
that, either.

Bobby

On Tue, 24 Feb 2009 04:47:00 -0600, Chris Pemberton <cjpembo 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 out?
>
> cjpembo
>

--
DrMajorBob at longhorns.com

```

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