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Timing of Table

  • To: mathgroup at smc.vnet.net
  • Subject: [mg43229] Timing of Table
  • From: "Mariusz Jankowski" <mjkcc at usm.maine.edu>
  • Date: Wed, 20 Aug 2003 22:25:35 -0400 (EDT)
  • Organization: University of Maine System/MSLN
  • Sender: owner-wri-mathgroup at wolfram.com

Dear Mathematica Users,

Can someone explain the timing difference between the following two code
samples. I am guessing it has to do with the auto-compiler, but even if I am
correct, I would like to know more.

Slow version:

n=m=100;
Timing[Do[Table[1,{i,1,n},{j,1,m}],{1000}];]



Fast version:

n=m=100;

Timing[Do[Table[1,{i,1,n},Evaluate[{j,1,m}]],{1000}];]

which is as fast as

Timing[Do[Table[1,{i,1,100},{j,1,100}]],{1000}];]

I also noticed that only the outermost iterator needs to be wrapped in
Evaluate. Why(?)



Thanks, Mariusz




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