MathGroup Archive 2004

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Slowdown

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53220] Slowdown
  • From: Maxim <ab_def at prontomail.com>
  • Date: Fri, 31 Dec 2004 03:47:44 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

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


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