Re: Curious Timing Results
- To: mathgroup at smc.vnet.net
- Subject: [mg38666] Re: [mg38651] Curious Timing Results
- From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
- Date: Sat, 4 Jan 2003 07:25:50 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
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.}
>
>
>