Re: Slowdown

• To: mathgroup at smc.vnet.net
• Subject: [mg53223] Re: Slowdown
• From: Peter Pein <petsie at arcor.de>
• Date: Sat, 1 Jan 2005 02:33:43 -0500 (EST)
• References: <cr33tt\$je6\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```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.
>
> Maxim Rytin
> m.r at inbox.ru
>
Your version of Mathematica may be too up to date ;-)

In[1]:=
\$Version
Out[1]=
"4.0 for Microsoft Windows (July 16, 1999)"
In[2]:=
Module[{f, L}, L = f[];
Do[L = f[L, i], {i, 10^6}]] // Timing
Out[2]=
{1.547 Second, Null}
In[3]:=
Module[{weirdness, L}, L = weirdness[];
Do[L = weirdness[L, i], {i, 10^6}]] // Timing
Out[3]=
{1.547 Second, Null}

--
Peter Pein
Berlin

```

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