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MathGroup Archive 2004

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Re: Another question about Compile[]:

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49967] Re: [mg49950] Another question about Compile[]:
  • From: DrBob <drbob at bigfoot.com>
  • Date: Sun, 8 Aug 2004 05:37:53 -0400 (EDT)
  • References: <200408070751.DAA07788@smc.vnet.net>
  • Reply-to: drbob at bigfoot.com
  • Sender: owner-wri-mathgroup at wolfram.com

myMgpp = Compile[
     {{n, _Integer}},
     Block[{p}, Do[If[PrimeQ[n - (p = Prime[i])], Return[p]], {i, PrimePi[n/2], 1, -1}]],
     {{i, _Integer}, {Prime[_], _Integer}, {PrimePi[_], _Integer}, {PrimeQ[_], True | False}}];
myMgpp[400]
173

Bobby

On Sat, 7 Aug 2004 03:51:48 -0400 (EDT), Gilmar Rodr?guez Pierluissi <gilmar.rodriguez at nwfwmd.state.fl.us> wrote:

> 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!
>
>
>



-- 
DrBob at bigfoot.com
www.eclecticdreams.net


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