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MathGroup Archive 2001

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Re: Can this be made cleaner and more efficient?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg29047] Re: Can this be made cleaner and more efficient?
  • From: "Orestis Vantzos" <atelesforos at hotmail.com>
  • Date: Sat, 26 May 2001 21:53:37 -0400 (EDT)
  • Organization: National Technical University of Athens, Greece
  • References: <9eksm9$7r9@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

This function test[n_], checks checks the factors of n,
With[{primes = Array[Prime, {24}]},
  test[res_] := Or @@ (Outer[Mod[#1, #2] == 0 &, {res}, primes] // Flatten)]

Now you can use this:
myRand[d_] :=
    NestWhile[Random[Integer, 10^(d - 1), 10^d}] &, 2, test, 1]

"Flip" <nospam at newsranger.com> wrote in message
news:9eksm9$7r9 at smc.vnet.net...
> Hi All,
>
> I was wondering if the following module (it is small) can be made simpler
and
> faster ... and thoughts would be appreciated.
>
> RandomOdd2[d_] := Module[{res},
> res = Random[Integer, {10^(d - 1), 10^d}];
> While[(
>
> Mod[res, 02] == 0 || Mod[res, 03] == 0 || Mod[res, 05] == 0 ||
> Mod[res, 07] == 0 || Mod[res, 11] == 0 || Mod[res, 13] == 0 ||
> Mod[res, 17] == 0 || Mod[res, 19] == 0 || Mod[res, 23] == 0 ||
> Mod[res, 29] == 0 || Mod[res, 31] == 0 || Mod[res, 37] == 0 ||
> Mod[res, 41] == 0 || Mod[res, 43] == 0 || Mod[res, 47] == 0 ||
> Mod[res, 53] == 0 || Mod[res, 59] == 0 || Mod[res, 61] == 0 ||
> Mod[res, 71] == 0 || Mod[res, 73] == 0 || Mod[res, 79] == 0 ||
> Mod[res, 83] == 0 || Mod[res, 89] == 0 || Mod[res, 97] == 0),
> res = Random[Integer, {10^(d - 1), 10^d}]];
> res]
>
> It is basically sieving out the first 24 primes (primes <= 100) from the
result.
>
> Thank you ... Flip
>
>




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