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Re: List concatenation speed

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87620] Re: List concatenation speed
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Mon, 14 Apr 2008 05:46:56 -0400 (EDT)
  • References: <ftsd1e$bba$1@smc.vnet.net>

Hi,

yes, forget Do[], erase it from your mind total!
And if you for some reason can't do that, try

ClearAll[poly]; poly = {};
Print[Timing[Do[poly = {poly, p}, {i, 1, n}]; Flatten[poly];]];

Regards
   Jens

carlos at colorado.edu wrote:
> 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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