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Re: Manually nested Tables faster than builtin nesting?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg113435] Re: Manually nested Tables faster than builtin nesting?
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 28 Oct 2010 04:28:29 -0400 (EDT)

I get similar results and Outer falls between the others.

imax = jmax = 5000;

(tabletable = Table[Table[i*j, {i, imax}], {j, jmax}];) // 
  Timing // First

1.96097

(table = Table[i*j, {i, imax}, {j, jmax}];) // Timing // First

24.0062

(outer = Outer[#1*#2 &, Range[imax], Range[jmax]];) // Timing // First

14.2569

tabletable == table == outer

True


Bob Hanlon

---- Sebastian Schmitt <sschmitt at physi.uni-heidelberg.de> wrote: 

=============
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



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