factor arbitrarily large numbers

* m4/gmp.m4: New file; adds cu_GMP, which detects GNU MP.
* configure.ac: Use cu_GMP.
* src/Makefile.am: Link factor against libgmp if available.
* src/factor.c: Use GNU MP if it is available.
(emit_factor, emit_ul_factor, factor_using_division,
factor_using_pollard_rho, extract_factors_multi,
sort_and_print_factors, free_factors): new functions
for the arbitrary-precision implementation, taken from an example
in GNU MP.
(factor_wheel): Renamed; was called factor.
(print_factors_single): Renamed; was called print_factors.
(print_factors): New function, chooses between the single- and
arbitrary-precision algorithms according to availability of GNU MP
and the length of the number to be factored.
(usage, main): New options --bignum and --no-bignum.
* coreutils.texi (factor invocation): Document new command-line
options for the MP implementation and update the performance
numbers to take into account the asymptotically faster algorithm.
* TODO: Remove item about factoring large primes (it's done).
* m4/gmp.m4: Add support for --without-gmp.
* NEWS: Mention the new feature.

1 files changed, 3 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 4637ebad9..bcbabb1a2 100644
--- a/NEWS
+++ b/NEWS
@@ -19,6 +19,9 @@ GNU coreutils NEWS                                    -*- outline -*-
   With this new option, after a short read, dd repeatedly calls read,
   until it fills the incomplete block, reaches EOF, or encounters an error.
 
+  factor accepts arbitrarily large numbers and factors them using
+  Pollard's rho algorithm.
+
   md5sum now accepts the new option, --quiet, to suppress the printing of
   'OK' messages.  sha1sum, sha224sum, sha384sum, and sha512sum accept it, too.