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Question: Compile in Mathematica 8.0

  • To: mathgroup at smc.vnet.net
  • Subject: [mg114631] Question: Compile in Mathematica 8.0
  • From: Asim <maa48 at columbia.edu>
  • Date: Sat, 11 Dec 2010 01:52:46 -0500 (EST)

Hi

I am not sure why the first function named v works and why the second
function named v1 does not compile. The only difference between the
two functions is in the variable called len which controls the number
of random numbers that are generated.

I am using Mathematica 8.0 on Windows Vista machine.

Thanks

Asim



First function:


v = Compile[{{n, _Integer}},
  Module[
   {g, len},
   len = n*(n - 1);
   g = RandomVariate[NormalDistribution[0., 1.], len]
   ]
  ]

Output is

CompiledFunction[{n},Module[{g,len},len=n
(n-1);g=RandomVariate[NormalDistribution[0.,1.],len]],-CompiledCode-]

v[3]

{0.0866864,-0.271121,-0.431317,-0.6787,-1.29246,0.550486}

Second Function:

v1 = Compile[{{n, _Integer}},
  Module[
   {g, len},
   len = n*(n - 1)/2;
   g = RandomVariate[NormalDistribution[0., 1.], len]
   ]
  ]

CompiledFunction[{n},Module[{g,len},len=1/2 n
(n-1);g=RandomVariate[NormalDistribution[0.,1.],len]],-CompiledCode-]

v1[3]

During evaluation of In[42]:= CompiledFunction::cfse: Compiled
expression {-0.325949,1.72381,0.368231} should be a machine-size
integer. >>

During evaluation of In[42]:= CompiledFunction::cfex: Could not
complete external evaluation at instruction 8; proceeding with
uncompiled evaluation. >>

Out[42]= {0.295626, 0.664446, 0.654626}





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