GNU bug report logs - #22567
Factoring 38 nines

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Message #18 received at 22567-done <at> debbugs.gnu.org (full text, mbox):

From: SasQ <sasq1 <at> go2.pl>
To: Eric Blake <eblake <at> redhat.com>, 22567-done <at> debbugs.gnu.org
Subject: Re: bug#22567: Factoring 38 nines
Date: Fri, 05 Feb 2016 19:30:21 +0100

2016.02.05 @ 18:55, Eric Blake wrote:

> The program is not hanging, just spending a LONG time. Some numbers
> are inherently easier to factor than others, when using
> currently-known non-quantum algorithms.
> 
> On my machine: $ time factor
> 99999999999999999999999999999999999999 
> 99999999999999999999999999999999999999: 3 3 11 909090909090909091 
> 1111111111111111111
> 
> real	0m45.630s user	0m45.684s sys	0m0.000s

OK, this convinces me this is not a bug. 4m30 on my machine.
But it's definitely a user-interface fail ;)
It should at least output some warning that the computations might
take longer, or display some progress status / estimated time along
the way.
Because otherwise the user can think it simply hangs.

> The source code is there for you to peruse.

There sure is, but analyzing it just to figure out the algorithm takes
much more time than refering the maual to see which particular
factorization algorithm or its variation is in use.

It took me a while to find the answer on StackOverflow:
http://stackoverflow.com/questions/11155331/what-is-the-algorithm-behind-the-factor-command-in-linux
so mentioning it in the man page wouldn't hurt.

Anyway, thanks for your detailed explanations.

-- 
SasQ

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