On Wed, Feb 25, 2015 at 10:15 AM, Michael Orlitzky <mich...@orlitzky.com> wrote:
> On 02/25/2015 12:55 PM, Jeroen Demeyer wrote:
>> Hello,
>>
>> Should there be code in Sage which is extremely slow and for educational
>> purposes only? I am talking about eratosthenes() which is just a very
>> slow alternative to prime_range().
>>
>> I would just remove that code, but maybe people have other opinions...
I also agree it is OK to have such *code*. However, to have it just
there without a name that strongly emphasizes its toy nature is very
bad. People often think that if f is a function defined in a
respectable math software system (Magma or Sage), then the performance
of f(n) is at least reasonable.
I think it's best to name any functionality that is "is extremely slow
and for educational
purposes" explicitly with "toy" somewhere in the name. If you do:
sage: search_src("toy")
you'll see this convention often in sage.
I would be for deprecating eratosthenes() and replacing it by something like
toys.eratosthenes()
or possibly eratosthenes_toy()...
I like the idea of a toys.[tab] that gathers together toy implementations...
>
> It's nice to leave in code like this and use it as part of the test
> suite. It would be easy to check that the sieve of Eratosthenes is
> correct, but prime_range() is a long chain of dark magic to me.
>
> A good test would be that they agree on the primes below (say) 1,000:
>
> sage: eratosthenes(1000) == prime_range(1000)
> True
>
> There are some tests for prime_range() already, e.g.
>
> sage: L = prime_range(25000,2500000)
> sage: len(L)
> 180310
>
> but who knows if the results are correct.
>
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William (http://wstein.org)
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