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MathGroup Archive 2005

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Re: Compile. Not again

  • To: mathgroup at smc.vnet.net
  • Subject: [mg56490] Re: [mg56470] Compile. Not again
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Tue, 26 Apr 2005 21:52:50 -0400 (EDT)
  • References: <200504260534.BAA14453@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

  Another strange (to me) observation: consider the following function g

g = CompiledFunction[{}, {{2, 1, 0}}, {0, 4, 0, 0, 1}, {{1, 5}, {7, 
{0}, 2,
     1, 0}, {4, 1, 0}, {64, 0, 0, 0, 0,
      1}, {4, 1, 0}, {4, 1, 2}, {24, 1, 2, 3}, {65, 0, 0, 0,
       0, 3}, {2}}, Function[{}, Module[{L = {0}}, L[[1]]++; L]], 
Evaluate]

g ought to be exactly the same as f (look at InputForm[f]). However 
every time you evaluate g[] you will get {1} (at least I do with 
Mathemaitca 5.1 on Mac OS X).

Anndrzej Kozlowski


On 26 Apr 2005, at 14:34, Maxim wrote:

> *This message was transferred with a trial version of CommuniGate(tm) 
> Pro*
> Here's what I get in version 5.1.0:
>
> In[1]:= f = Compile[{}, Module[{L = {0}}, L[[1]]++; L]]
>
> In[2]:= a = f[]
>
> Out[2]= {1}
>
> In[3]:= b = f[]
>
> Out[3]= {2}
>
> In[4]:= Table[f[], {3}]
>
> Out[4]= {{5}, {5}, {5}}
>
> In[5]:= {a, b}
>
> Out[5]= {{5}, {5}}
>
> Each subsequent call to f uses the modified value of L. This also 
> affects
> Table and all the objects involved in assignments such as x = f[] (but 
> not
> x = f[][[1]]), including DownValues[Out]. The problem might be related 
> to
> deciding whether a and b point to the same shared object.
>
> Maxim Rytin
> m.r at inbox.ru
>


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