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Re: Timing graphics in the real world

  • To: mathgroup at smc.vnet.net
  • Subject: [mg123000] Re: Timing graphics in the real world
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Sun, 20 Nov 2011 05:35:35 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <201111191145.GAA18886@smc.vnet.net>
  • Reply-to: drmajorbob at yahoo.com

A quote from Help:

"AbsoluteTiming[expr] measures only the time involved in actually  
evaluating expr, not time involved in formatting the result."

Graphics rendering occurs in the FrontEnd, not the Kernel, so  
AbsoluteTiming doesn't count it.

Bobby

On Sat, 19 Nov 2011 05:45:59 -0600, Ralph Dratman  
<ralph.dratman at gmail.com> wrote:

> I am trying to find out why a piece of 3D graphics code takes a long
> time when scaled up to a lot of little objects. For this purpose I
> begin by timing ten runs of a small instance. Here's what my function
> calls look like:
>
> noneOfThat[] :=
>  Module[{}, {drawSolidCube[], drawSolidCube[], drawSolidCube[],
>    drawSolidCube[], drawSolidCube[], drawSolidCube[], drawSolidCube[],
>     drawSolidCube[], drawSolidCube[], drawSolidCube[]}]
>
> where SolidCube is actually not solid, but rather an aggregate of
> about 20 cubelets per image in this first test case.
>
> AbsoluteTiming[noneOfThat[]]
> {0.072105,  ...}
>
> or if you prefer,
>
> Timing[noneOfThat[]]
> {0.071197,  ...}
>
> The timing answers are consistent within about 10% across several tries.  
> Nice.
>
> Just one problem: here in my universe, on a Core Duo Mac Mini at 2.4
> GHz with about 2 GB of free memory, the actual process described above
> takes about 10 seconds. The cores stay at around 50% usage (each)
> while this is happening. Drawing is taking about 140 times longer than
> Mathematica says!
>
> Next I try the same task with a 2x increase in linear size of the
> cube, leading to an 8x increase in volume and number of objects, with
> again 10 repetitions in straight-line Mathematica code.
>
> AbsoluteTiming then says 0.62970 while Timing says 0.574067, both in
> the neighborhood of 8 times the earlier figures. Real-world time is
> about 85 seconds, also in line with the 8x scaling.
>
> Again the processors seem to be about half busy, and once again it
> takes about 140 times as long to do the real drawing as Mathematica
> reports.
>
> I'm speculating all this means Mathematica is sending my graphics
> hardware a bunch of asynchronous drawing calls while simultaneously
> announcing, "Done!"
>
> I infer that a faster graphics card might make a world of difference.
> To make that possible, I could switch to a Windows or Linux system if
> necessary.
>
> If possible, I would like the new real-world drawing time to be at
> least ten times better than the figures reported here.
>
> Comments, please? I would be particularly interested to learn about
> any specific hardware that might improve the speed.
>
> Thank you very much.
>
> Ralph Dratman
>


-- 
DrMajorBob at yahoo.com



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