.. _spkg_ecm:

ecm: Elliptic curve method for integer factorization
====================================================

Description
-----------

GMP-ECM - Elliptic Curve Method for Integer Factorization

Sources can be obtained from http://gforge.inria.fr/projects/ecm/

License
-------

LGPL V3+


Upstream Contact
----------------

-  ecm-discuss@lists.gforge.inria.fr (requires subscription)

Dependencies
------------

-  GMP/MPIR (Note: Python is \*not\* required for ordinary builds.)
-  GNU patch


Special Update/Build Instructions
---------------------------------

-  GMP-ECM comes with a self-tuning feature; we could support
   that as an option ($SAGE_TUNE_*=yes) in the future.

-  ECM currently does not (by itself) use the CC and CFLAGS settings
   from 'gmp.h' since we pass (other) options in CFLAGS, and CC is set
   by Sage and might got set by the user. We now at least partially fix
   that
   such that "optimized" code generation options ('-mcpu=...',
   '-mtune=...')
   are used by gcc.
   Of course a user can also manually enable them by setting the
   "global"
   CFLAGS to e.g. '-march=native' on x86[_64] systems, or '-mcpu=...'
   and
   '-mtune=...' on other architectures where "native" isn't supported.
   Note that this doesn't affect the packages' selection of processor-
   specific optimized [assembly] code.
   'spkg-install' already reads the settings from Sage's and also a
   system-wide GMP / MPIR now, but doesn't (yet) use all of them.
   If SAGE_FAT_BINARY="yes", we should avoid too specific settings of
   "-mcpu=...", and perhaps pass a more generic "--host=..." to
   'configure'. (MPIR honors '--enable-fat' to some extent, but this
   option isn't used on anything other than x86 / x86_64.)

-  We currently work around a linker bug on MacOS X 10.5 PPC (with
   GCC 4.2.1) which breaks 'configure' if debug symbols are enabled.
   This \*might\* get fixed in later upstream releases.

-  We could save some space by removing the ``src/build.vc10/``
   directory which
   isn't used in Sage. (It gets probably more worth in case also
   directories /
   files for later versions of Microsoft Visual C get added.)

Type
----

standard


Version Information
-------------------

package-version.txt::

    7.0.4.p2


Equivalent System Packages
--------------------------

conda:

.. CODE-BLOCK:: bash

    $ conda install ecm-devel

Debian/Ubuntu:

.. CODE-BLOCK:: bash

    $ sudo apt-get install  ecm-devel

Fedora/Redhat/CentOS:

.. CODE-BLOCK:: bash

    $ sudo yum install  ecm-devel

freebsd:

.. CODE-BLOCK:: bash

    $ sudo pkg install ecm-devel

nix:

.. CODE-BLOCK:: bash

    $ nix-env --install ecm-devel

void:

.. CODE-BLOCK:: bash

    $ sudo xbps-install  ecm-devel

See https://repology.org/project/ecm-devel/versions

If the system package is installed, ./configure will check whether it can be used.