On Fri, Jul 25, 2008 at 11:57 AM, Jim Meyering <[EMAIL PROTECTED]> wrote: > 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
I have a working GMP-based version (essentially, it's the example taken from the GMP docs that you mentioned earlier). For the moment, the code always uses GMP if it's available. The GMP version is dramatically faster for the pathalogical case mentioned in the docs, and about 2x slower for "easy" cases with small integers. ~/source/GNU/coreutils/coreutils$ time ./src/factor 18446744073709551557 18446744073709551557: 18446744073709551557 real 0m0.003s user 0m0.000s sys 0m0.008s ~/source/GNU/coreutils/coreutils$ time factor 18446744073709551557 18446744073709551557: 18446744073709551557 real 0m34.792s user 0m34.794s sys 0m0.004s ~/source/GNU/coreutils/coreutils$ wc -l 1m 1000000 1m ~/source/GNU/coreutils/coreutils$ time factor < 1m >/dev/null real 0m2.668s user 0m2.660s sys 0m0.012s ~/source/GNU/coreutils/coreutils$ time ./src/factor < 1m >/dev/null real 0m5.607s user 0m4.012s sys 0m1.584s ~/source/GNU/coreutils/coreutils$ uniq < 1m 1000000000 Given these performance characteristics, I would not be adverse to using the GMP implementation for all sizes of input. However, there is also the maintenance consideration. We must maintain a non-GMP implementation for systems which lack GMP (or decline to use it). I would in general be concerned about bit-rot in the non-GMP implementation, so I guess it's worth using it unconditionally for some subset of inputs in order to be sure it really works for those who must use it. What do you think? Thanks, James. _______________________________________________ Bug-coreutils mailing list Bug-coreutils@gnu.org http://lists.gnu.org/mailman/listinfo/bug-coreutils
