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## Re: factor inconsistencies/limits?

**From**: |
Jim Meyering |

**Subject**: |
Re: factor inconsistencies/limits? |

**Date**: |
Fri, 25 Jul 2008 12:57:54 +0200 |

Linda Walsh <address@hidden> wrote:
>* I was just watching google desktop -- that's supposed to index in background*
>* using up 75% of my cpu(s) (3 out of 4) and wanted to try something*
>* cpu-intensive to see if it would back-off (it doesn't).*
>
>* I decided maybe factoring a large int might do the trick. So I popped into my*
>* "cygwin/win32" window and started trying numbers with factor.*
Size isn't the problem. e.g, 2^64-1 is factored almost immediately.
However, it takes much longer to factor the worst-case number,
18446743979220271189, which is smaller.
See "info coreutils factor" for details.
Factor should work fine up to 2^64-1:
# factor $(echo 2^64-1|bc)
18446744073709551615: 3 5 17 257 641 65537 6700417
Actually, I've wanted coreutils' factor program to work
with arbitrary-precision numbers for a long time.
This is mentioned briefly in TODO. For more detail, see these
search results:
http://search.gmane.org/search.php?group=gmane.comp.gnu.coreutils.bugs&query=factor+gmp