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MathGroup Archive 2004

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Re: Direct Memory Replacing in Array

  • To: mathgroup at smc.vnet.net
  • Subject: [mg46830] Re: Direct Memory Replacing in Array
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Tue, 9 Mar 2004 19:57:25 -0500 (EST)
  • Organization: Universitaet Leipzig
  • References: <c2k4q5$qq0$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

assign a Part of the matrix ?

$HistoryLength=0;

m=Table[0,{10000},{10000}]
m[[5,All]]=Table[1,{10000}]

Regards
  Jens


Jeremy Fox wrote:
> 
> The Mathematica syntax
> 
> mat = ReplacePart[mat,new,index]
> 
> is clean. However, it probably involves a complete replacing of the
> entire, old mat with the entire new mat, in memory. This operation is
> expensive if the user is interested in changing only a small part of a
> large array mat.
> 
> Is there a way to change small numbers of elements in an array without
> requiring the other elements to be copied again? This is how low-level
> languages such a C and Fortran work.
> 
> Jeremy


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