Re: Slowdown

*To*: mathgroup at smc.vnet.net*Subject*: [mg53242] Re: Slowdown*From*: Peter Pein <petsie at arcor.de>*Date*: Sun, 2 Jan 2005 04:12:52 -0500 (EST)*References*: <cr5k8m$18l$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

yehuda ben-shimol wrote: ... > Since you need to observe it yourself, on your machine, I suggest that you > run the following code and check the (emuzing) results yourself. > > > t = CharacterRange["a", "z"]; > Do[fname = StringJoin[t[[Table[Random[Integer, {1,26}], {i}]]]]; > Print[i, "\t", fname, "\t", > Timing[ > Module[{fs = ToExpression[fname], L}, > L = fs[]; > Do[L = fs[L, j], {j, 10^4}]]]], {i, 1, 50}, {5}] > > This rather simple "computer experiment" on Mathematica (as S. Wolfram might > say) shows that the timing problem is not dependent on the length of the > function name (at least until length 50 that I checked). > I couldn't believe that the performance depends on the function's name?????? > Can we get a comment from one of the WRI professionals on that issue? > yehuda > That's funny. I just have been lucky not to get trapped? I modified your code to generate function names consisting of n times the same letter. Here's what I got for the length of the name from 1 to 50 (Mathematica 4): In[1]:= tlist = Complement[Join[CharacterRange["a", "z"], CharacterRange["A", "Z"]], ToString /@ {B, C, D, E, I, M, N, O, V}]; weird[n_] := Extract[ToExpression[tlist], Position[ (1/Second*First[Timing[ Module[{fs = ToExpression[StringJoin @@ Table[#1,{n}]], L}, L = fs[]; Do[L = fs[L, j], {j, 1000}]]]] & ) /@ tlist, x_ /; x > 0.02 (*adjust this*)]]; wlist = weird /@ Range[12] Out[3]= {{J, l, L, w, W, y, Y}, {j, J, l, L, w, W, y, Y}, {j, J, l, L, w, W, y, Y}, {g, G, m, t, T, z, Z}, {g, G, m, t, T, z, Z}, {g, G, m, t, T, z, Z}, {g, G, m, t, T, z, Z}, {}, {}, {}, {}, {j, J, l, L, w, W, y, Y}} For k>=1 the "slow" letters are the same for the lengths 4k..4k+3: In[4]:= weird /@ Range[396, 403] Out[4]= {{j, J, l, L, w, W, y, Y}, {j, J, l, L, w, W, y, Y}, {j, J, l, L, w, W, y, Y}, {j, J, l, L, w, W, y, Y}, {g, G, t, T, z, Z}, {g, G, t, T, z, Z}, {g, G, t, T, z, Z}, {g, G, t, T, z, Z}} strange, isn't it? -- Peter Pein Berlin