Re: RE: puzzling difference in speed

*To*: mathgroup at smc.vnet.net*Subject*: [mg34795] Re: [mg34737] RE: [mg34688] puzzling difference in speed*From*: "Fred Simons" <f.h.simons at tue.nl>*Date*: Fri, 7 Jun 2002 01:08:58 -0400 (EDT)*References*: <200206040741.DAA03886@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hartmut Wolf remarked with respect to the given examples:: > Obviously the computing machinery for Array behaves differently when the > dimensions are given explicitly or introduced as an expression (to be > evaluated) > It seems to be more complicated. Have a look at the following results: In[1]:= n=100; t1 = Table[0, {n},{n},{n}]; In[2]:= t = array[Plus, Dimensions[t1]]; u = array[Plus, {100, 100, 100}]; Equal[t, u] Out[4]= True In[5]:= ReplaceAll[t, array\[Rule]Array]; // Timing ReplaceAll[u ,array\[Rule]Array]; // Timing Out[5]= {0.65 Second,Null} Out[6]= {0.77 Second,Null} In[7]:= Apply[Array, t]; // Timing Apply[Array, u]; // Timing Out[7]= {4.51 Second,Null} Out[8]= {0.72 Second,Null} Despite the fact that t equals u, we have the same difference in timing. Does Mathematica 'remember' the way the expression t has been computed? Fred Simons Eindhoven University of Technology

**References**:**RE: puzzling difference in speed***From:*"Wolf, Hartmut" <Hartmut.Wolf@t-systems.com>