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 >> >