Re: Manually nested Tables faster than builtin nesting?
- To: mathgroup at smc.vnet.net
- Subject: [mg113434] Re: Manually nested Tables faster than builtin nesting?
- From: Sebastian Schmitt <sschmitt at physi.uni-heidelberg.de>
- Date: Thu, 28 Oct 2010 04:28:18 -0400 (EDT)
Hi Tomas!
With "manually" I mean
"Table[Table[..., {i, imax}], {j, jmax}]"
(two Tables explicitly/manually)
instead of
"Table[..., {i, imax}, {j, jmax}]"
(one Table but two iterators).
Can you explain the difference in speed?
Cheers,
Sebastian
PS:
$Version
"7.0 for Linux x86 (64-bit) (February 18, 2009)"
$ grep "model name" /proc/cpuinfo
model name : Intel(R) Core(TM)2 Duo CPU P8600 @ 2.40GHz
model name : Intel(R) Core(TM)2 Duo CPU P8600 @ 2.40GHz
Tomas Garza wrote:
> You must have a very fast machine! Any way, I get 5.647 and 43.134, respectively. The factor in both machines is close to 8, not 2 (what do you mean manually?)
>
> -Tomas
>
>> Date: Wed, 27 Oct 2010 05:13:59 -0400
>> From: sschmitt at physi.uni-heidelberg.de
>> Subject: [mg113391] Manually nested Tables faster than builtin nesting?
>> To: mathgroup at smc.vnet.net
>>
>> Dear all!
>>
>> I find that manually nested Tables are faster (factor 2 in my example)
>> compared to the builtin nesting. I probably do a stupid thinko. Could
>> you please have a look?
>>
>> In[52]:= imax = jmax = 5000;
>>
>> In[53]:= (tabletable = Table[Table[i*j, {i, imax}], {j, jmax}];) //
>> Timing // First
>>
>> Out[53]= 1.84
>>
>> In[54]:= (table = Table[i*j, {i, imax}, {j, jmax}];) // Timing // First
>>
>> Out[54]= 14.55
>>
>> In[55]:= tabletable == table
>>
>> Out[55]= True
>>
>> Thanks,
>>
>> Sebastian
>>
>