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MathGroup Archive 2005

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Re:Re: Vectorization

  • To: mathgroup at smc.vnet.net
  • Subject: [mg60821] Re:[mg60648] Re: Vectorization
  • From: "Marcelo Mayall" <mmayall at bol.com.br>
  • Date: Thu, 29 Sep 2005 05:42:05 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Dear Jean-Marc Gulliet,

At least in my computer, it seems that the pattern is accordingly as what I had described:

In[1]:=
Table[Table[Sin[N[I] Random[]],{300000}]//Timing//First,{5}]
Table[Sin[Table[N[I] Random[],{300000}]]//Timing//First,{5}]

Out[1]=
{0.312 Second,0.329 Second,0.328 Second,0.312 Second,0.328 Second}

Out[2]=
{0.297 Second,0.297 Second,0.297 Second,0.312 Second,0.297 Second}

In[3]:=
Table[Table[Sin[Random[]],{1000000}]//Timing//First,{5}]
Table[Sin[Table[Random[],{1000000}]]//Timing//First,{5}]

Out[3]=
{0.328 Second,0.329 Second,0.328 Second,0.328 Second,0.328 Second}

Out[4]=
{0.234 Second,0.219 Second,0.234 Second,0.219 Second,0.235 Second}


Regards,

Marcelo Mayall




---------- Início da mensagem original ----------- 
De: "Jean-Marc Gulliet" jeanmarc.gulliet at gmail.com 
Para: mathgroup at smc.vnet.net 
Data: Fri, 23 Sep 2005 04:19:52 -0400 (EDT) 
Assunto: [mg60648] Re: Vectorization 
> Marcelo Mayall wrote: 
> > It's possible to initialize a vector starting from an elementary functions: 
> > 
> > In[1]:= 
> > Table[Sin[Random[]],{10000000}]//Timing//First 
> > 
> > Out[1]= 
> > 3.203 Second 
> > 
> > The same problem can be done a bit more efficiently if the elementary function is applied to the numerical vector: 
> > 
> > In[2]:= 
> > Sin[Table[Random[],{10000000}]]//Timing//First 
> > 
> > Out[2]= 
> > 1.969 Second 
> > 
> > But why the tendency is opposed when the numbers are complex ? Is this a bug ? 
> > 
> > In[3]:= 
> > Table[Sin[I Random[]],{1000000}]//Timing//First 
> > Sin[Table[I Random[],{1000000}]]//Timing//First 
> > 
> > Out[3]= 
> > 2.484 Second 
> > 
> > Out[4]= 
> > 2.656 Second 
> > 
> > 
> > Thanks, 
> > 
> > Marcelo Mayall 
> > 
> Compare the following results: 
> 
> In[1]:= 
> Table[Sin[I Random[]],{1000000}]//Timing//First 
> Sin[Table[I Random[],{1000000}]]//Timing//First 
> 
> Out[1]= 
> 2.688 Second 
> 
> Out[2]= 
> 2.703 Second 
> 
> In[3]:= 
> Table[Sin[I Random[]],{1000000}]//Timing//First 
> Sin[Table[I Random[],{1000000}]]//Timing//First 
> 
> Out[3]= 
> 2.656 Second 
> 
> Out[4]= 
> 2.547 Second 
> 
> What do you conclude :-) Don't you you think than more than a couple of 
> tests would be necessary to get a statistically significant result? 
> 
> /J.M. 
> 
> 


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