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MathGroup Archive 2008

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List concatenation speed

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87571] List concatenation speed
  • From: carlos at Colorado.EDU
  • Date: Sun, 13 Apr 2008 03:32:46 -0400 (EDT)

I am building mesh plots that require concatenation of thousands of
Graphics objects into one list for Show[].  This is done by appending
objects as they are created, and there are several ways to do that.
Tested 3 of them for speed using a simple object:

     p=Table[x,{50}]; n=10000;
     ClearAll[poly]; poly={};
     Print[Timing[Do[AppendTo[poly,p],{i,1,n}]]];
     ClearAll[poly]; poly={};
     Print[Timing[Do[poly=Append[poly,p],{i,1,n}]]];
     ClearAll[poly]; poly={};
     Print[Timing[Do[poly=Join[poly,{p}],{i,1,n}]]];

{5.8395 Second,Null}
{5.7206 Second,Null}
{6.29728 Second,Null}

Tests were run on version 5.2 on a G5 desktop Mac. I expected Join to
win,
but it didnt.  Is there a faster way?


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