Fw: Re: Curious Timing Results
- To: mathgroup at smc.vnet.net
- Subject: [mg38743] Fw: [mg38666] Re: [mg38651] Curious Timing Results
- From: 최정규 <cjk2807 at pslab.snu.ac.kr>
- Date: Tue, 7 Jan 2003 07:32:08 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
Dear Andrzej Kozlowski
At first, I am so grateful to your reply which helped me with some stuffs.
Anyway, tracing the inputs, I found something strange to me.
That is, I've got "In[3]:= SameQ[x,y] -> Out[3]= False" , not "In[3]:= SameQ[x,y] -> Out[3]= True"
I can't understand it.
Jungkyu Choi
Seoul, South-Korea.
e-mail: cjk2807 at hotmail.com
----- Original Message -----
From: "Andrzej Kozlowski" <akoz at mimuw.edu.pl>
To: mathgroup at smc.vnet.net
Subject: [mg38743] [mg38666] Re: [mg38651] Curious Timing Results
> You can see the difference as follows:
>
> In[17]:=
> <<Developer`
>
> In[18]:=
> x = Table[2.,{i,100000}];
>
> In[19]:=
> PackedArrayQ[x]
>
> Out[19]=
> True
>
> In[20]:=
> y = Table[If[i<1000000,2.,i],{i,100000}];
>
> In[21]:=
> PackedArrayQ[y]
>
> Out[21]=
> False
>
> THe need to unpack a packed array makes the first code run slower.
>
>
> Andrzej Kozlowski
> Yokohama, Japan
> http://www.mimuw.edu.pl/~akoz/
> http://platon.c.u-tokyo.ac.jp/andrzej/
>
>
>
>
> On Friday, January 3, 2003, at 02:15 PM, Chris Grant wrote:
>
> >
> > I find the Timing results below a little curious. Is there a simple
> > explanation why I shouldn't?
> >
> > Chris Grant
> >
> > In[1]:= x = Table[2.,{i,100000}];
> >
> > In[2]:= y = Table[If[i<1000000,2.,i],{i,100000}];
> >
> > In[3]:= SameQ[x,y]
> >
> > Out[3]= True
> >
> > In[4]:= Timing[Inner[Divide,x,x]]
> >
> > Out[4]= {0.44 Second,100000.}
> >
> > In[5]:= Timing[Inner[Divide,y,y]]
> >
> > Out[5]= {0.321 Second,100000.}
> >
> >
> >
>