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MathGroup Archive 1999

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Where's the Speed?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg19764] Where's the Speed?
  • From: "Kevin J. McCann" <kevin.mccann at jhuapl.edu>
  • Date: Wed, 15 Sep 1999 03:53:10 -0400
  • Organization: Johns Hopkins University Applied Physics Lab, Laurel, MD, USA
  • Sender: owner-wri-mathgroup at wolfram.com

I have read and heard a lot of hype about Mathematica 4.0

"featuring a
     New Generation of
                    Fast Numerics"

e.g. on www.wri.com .

However, in the real world it is hard to find anything to get excited about.
I have had several disappointing results from 4.0, here are the latest:

On a P450/NT I ran a very simple Crank-Nicholson integration of a
one-dimensional quantum free-particle wave-packet with x-dimensioned to 1001
points and time to 401 points -  no error checks or adaptive stepsize, just
plug-and-chug.  Runtime under 4.0 was 501 seconds, 3.0 was 480 seconds, but
who's quibbling; however, in FORTRAN this ran in 8 seconds.  I don't even
consider this to be "fast numerics", but 501 seconds sure isn't. I would
like to know where all this speed is so I can use some of it, or am I
missing something?

When I ran the FORTRAN code and then read it into Mathematica, it still was faster
than the Mathematica code alone, although the ReadList I used on the ASCII
file did take some time.  When I upped the dimensions to 2001 x 1001, the
FORTRAN ran in about 40 s - most of this is for the output; however, when I
tried to read it in to Mathematica, it took forever, and on the subsequent plot it
bombed the Kernel.  I then made the mistake of saving the NB which managed
to acquire an error so that I can't open it anymore - 6 Mb of useless NB!



--

Kevin J. McCann
Johns Hopkins University APL





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