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MathGroup Archive 1998

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Re: Making a large matrix

  • To: mathgroup at smc.vnet.net
  • Subject: [mg14856] Re: Making a large matrix
  • From: "Allan Hayes" <hay at haystack.demon.co.uk>
  • Date: Fri, 20 Nov 1998 02:17:02 -0500
  • References: <72tt72$isd@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Ersek, Ted R wrote in message <72tt72$isd at smc.vnet.net>...
>Consider the timing experiments below for making a large matrix of
>random real numbers.
>
>In[1]:=
>Table[Table[Random[],{1000}],{500}];//Timing Out[1]=
>{17.47 Second,Null}
>
>In[2]:=
>Table[Range[Random[],1000],{500}];//Timing Out[2]=
>{9.56 Second,Null}
>
>In[3]:=
>MakeMatrix=Compile[{m,n},Table[Range[Random[],n],{m}]];
>      (* Make an (m,n) matrix.  *)
>
>In[4]:=
>MakeMatrix[500,1000];//Timing
>Out[4]=
>{5.82 Second,Null}
>
>The last method is the fastest method I can come up with.   Can any of
>you find a faster way to make a large matrix with Mathematica? (short
>of using MathLink to run an executable program).
>
>Cheers,
>Ted Ersek
>
>

Ted,

Range[Random[], 1000] does not give random entries:

Range[Random[], 6]

{0.77037,1.77037,2.77037,3.77037,4.77037,5.77037}

Allan

---------------------
Allan Hayes
Mathematica Training and Consulting
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565




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