Re: Re: Slowdown

*To*: mathgroup at smc.vnet.net*Subject*: [mg53254] Re: [mg53241] Re: Slowdown*From*: yehuda ben-shimol <benshimo at bgu.ac.il>*Date*: Mon, 3 Jan 2005 04:29:31 -0500 (EST)*References*: <cr33tt$je6$1@smc.vnet.net> <200501020912.EAA27775@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi Roland, I'm afraid this is not true. Just try to run the code I sent with my post. "weirdness" was time consuming while weirdness1 was not. In addition it happened (not consistently) that function name of a SINGLE character suffered from this behavior as well. the code is given below for your convenience. 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, 104}]]]], {i, 1, 50}, {5}] yehuda Roland Franzius wrote: >Maxim wrote: > > >>Consider: >> >>In[1]:= >>Module[{f, L}, >> L = f[]; >> Do[L = f[L, i], {i, 10^4}] >>] // Timing >> >>Module[{weirdness, L}, >> L = weirdness[]; >> Do[L = weirdness[L, i], {i, 10^4}] >>] // Timing >> >>Out[1]= >>{0.015*Second, Null} >> >>Out[2]= >>{3.063*Second, Null} >> >>Here the timings differ by a factor of 200. Besides, the timing grows >>linearly in the first case and quadratically in the second (therefore, for >>n=10^5 there will be an approximately 2000 times slowdown). We can only >>guess that something goes wrong with the symbol name hashing. >> >> > >The timing difference occurs when the symbol "wierdness" exceeds 8 >characters. Test it for "wierdnes". That seems to be a consequence of >the machine routine for string comparison. Up to 8 characters can be >used without using a memory to memory compare. Of course it should be >possible to write a compare routine that makes not such a bit step. >

**Follow-Ups**:**Re: Re: Re: Slowdown***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>

**References**:**Re: Slowdown***From:*Roland Franzius <roland.franzius@uos.de>