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MathGroup Archive 2004

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Re: Another question about Compile[]:

  • To: mathgroup at smc.vnet.net
  • Subject: [mg50056] Re: Another question about Compile[]:
  • From: "Mariusz Jankowski" <mjankowski at usm.maine.edu>
  • Date: Fri, 13 Aug 2004 05:56:05 -0400 (EDT)
  • Organization: University of Southern Maine
  • References: <cf22mp$7si$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Gilmar, the first argument of Compile is the input list, so variables p and
q should be removed. Try

mgppp = Compile[{ {n, _Integer, 1}}, etc...]


However, I suspect your compiled code will be slower. Most of the work is
done inside kernel functions, which I suspect cannot be made faster by
wrapping with compile.

Regards, Mariusz




>>> Gilmar Rodr?guez Pierluissi<gilmar.rodriguez at nwfwmd.state.fl.us>
8/7/2004 4:08:57 AM >>>
Dear Mathematica Web Group:
I'm attempting to build a Compiled version of the following function:

In[1]:
MGPPP[n_] := Module[{p, q},
    {m = n/2; If[Element[m, 
    Primes], {p = m, q = m}, {k =
       PrimePi[m]; Do[If[Element[n - Prime[i], Primes], hit = i; 
          Break[]], {i, k, 1, -1}], p = Prime[hit], q = n - p}]}; {p, q}]

which works as follows:

In[2]:
MGPPP[400]

Out[2]:
{173, 227}

Unfortunately, my attempt fails:

In[3]:
mgppp = Compile[{{p, _Integer, 
    1}, {q, _Integer, 1}, {n, _Integer, 1}}, Module[{p, q},
      {m = n/2; If[Element[m, Primes], {p = m, q = m}, {
    k = PrimePi[m]; Do[If[Element[n - Prime[i], 
      Primes], hit = i; 
        Break[]], {i, k, 1, -1}], p = Prime[hit], q = n - p}]}; {p, q}]]

Out[3]:
Compile::initvar: The variable p has not been initialized or has been \
initialized to Null.
Compile::cptype: List not supported for type Void; evaluation will use the
\
uncompiled function.

Thank you for your help!




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