Re: List concatenation speed

*To*: mathgroup at smc.vnet.net*Subject*: [mg87649] Re: [mg87571] List concatenation speed*From*: János <janos.lobb at yale.edu>*Date*: Tue, 15 Apr 2008 05:48:55 -0400 (EDT)*References*: <200804130732.DAA11515@smc.vnet.net>

On Apr 13, 2008, at 3:32 AM, 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? Here is a newbie approach: > In[14]:= > Timing[Reap[i = 1; > While[i <= n, Sow[p]; > i++; ]]; ] > Out[14]= > {0.11680799999999891*Second, > Null} For comparison: In[6]:=Timing[Do[AppendTo[poly, p], {i, 1, n}]] Out[6]={6.827495*Second, Null} J=E1nos > In[24]:= > $Version > Out[24]= > "5.2 for Mac OS X (64 bit) \ > (June 20, 2005)"

**References**:**List concatenation speed***From:*carlos@Colorado.EDU