CoCoA is a freely available system for computing with multivariate
polynomials.
More specifically, CoCoA deals with
computations in multivariate polynomial rings over the rationals or
modular integers, and on their ideals and modules. The implementation
of the ideal/module theoretic operations relies on Gröbner basis
theory.
One of CoCoA's most important features is its high-level
programming language which allows the user to write his own
functions and to guide the system through complicated and involved
computations. This language has been designed to be natural and
intuitive, so it is easy to learn and is well suited to teaching. The
language is interpreted; its syntax is Pascal-like.
The main users of CoCoA are researchers in Commutative Algebra
and Algebraic Geometry together with their students. However,
computational algebraic techniques are spreading to other
fields (for instance numerical analysis, cryptography,
statistics, and dynamical systems), and consequently so is the realm
of application of CoCoA.
The system includes complete on-line help
(also available in html and
pdf) formats. CoCoA is
freely available software for research and
educational purposes which can be obtained by
http://cocoa.dima.unige.it
as well as from the mirror site in America
ftp://ftp.reed.edu/mirrors/cocoa
For convenience, the system offers a textual interface, an Emacs mode,
and a graphical user interface common to most platforms.
CoCoA is mentioned in some of the
most widely used text books in
Computational Algebra, and plays a major role in the
books Computational Commutative Algebra
(1 and 2) by Martin Kreuzer and
Lorenzo Robbiano.
The CoCoA project began in 1987. Initially it comprised just a
small program in Pascal running only on Macintoshes, and written
simply to enable the authors to experiment with Buchberger's algorithm
for computing Gröbner bases. Within two years it had become widely
used in many countries both for research and teaching. Later the
program was translated into C, and ported to other platforms. As its
range of abilities grew so did its use by researchers and
teachers.
The most recent versions benefit from development
directed at areas too often neglected in academic environments
notwithstanding their unquestionably vital contributions to the
usefulness of the program: e.g. robustness, natural syntax for
(computer-shy)
mathematicians, a sophisticated (graphical) user
interface, and comprehensive documentation. Naturally,
there has also been continual development in more academically
"respectable" areas, often spurred on by symbiosis with researchers
using CoCoA not only in algebraic geometry but also in other fields
such as mathematical analysis, and statistics.
An important purpose of the CoCoA program is to provide a
"laboratory" for studying computational commutative algebra: it
together with Singular and Macaulay 2 form an elite group of highly
specialized systems having as their main forte the capability to
calculate Gröbner bases. Although a number of general purpose
symbolic computation systems (e.g. REDUCE and Maple) do offer the
possibility of computing Gröbner bases, their non-specialist nature
implies a number of severe compromises which make them far less
suitable to act as a laboratory: e.g. relatively poor execution speed
and limited control over the algorithm parameters.
Aside from computing Gröbner bases CoCoA's particular strengths
include polynomial factorization, exact linear algebra,
Hilbert functions, toric ideals, and ideals of zero-dimensional schemes.
Aside from the normal development, a number of more specific plans are
afoot to improve and extend CoCoA: the choice of coefficients is to
be widened to handle parameters and finite algebraic extensions; and
the new mathematical core is already freely available as a GPL
software library written in C++, CoCoALib, facilitating integration
into other systems.
CoCoA works with multivariate polynomials over the fields of
modular integers or rational numbers (exact rationals, not floating
point numbers). Naturally, basic arithmetic operations are provided
together with more advanced operations such as GCD, composition, and
factorization.
The default ring environment is Q[x,y,z], but one may declare and
activate another polynomial ring (via the command Use). Data
may be transferred from one ring to another by defining and applying a
k-algebra homomorphism (via the command Image).
Gröbner bases and Orderings
The key tool for effective computations in Commutative Algebra is the
concept of Gröbner Basis. Almost every ideal and module theoretic
operation is realized via some Gröbner Basis computations: these
are effected by Buchberger's Algorithm whose worst-case
complexity is quite high (in fact, doubly exponential in the number of
variables). Therefore an efficient implementation of the Buchberger's
Algorithm is the heart of any Commutative Algebra System.
To perform Gröbner basis computations it is necessary to specify a
term-ordering, i.e. a total ordering which is compatible
with multiplication, and such that each indeterminate is bigger than 1.
Such orderings are characterized by suitable matrices.
Different orderings may lead to different Gröbner bases
for the same ideal with quite different computational costs (in space
and time).
CoCoA offers some pre-defined orderings and the ability to specify
any matrix-defined term-ordering.
Ideal and module operations
Among the types implemented in CoCoA there are ideals and
submodules of a free finitely generated module over
a polynomial ring. Basic operations on these objects
are performed via Gröbner basis computations (e.g. intersection,
elimination and saturation, radical membership, free
resolution of ideals or modules).
Extensive information about the CoCoA system and its
associated research
is available at the web site
http://cocoa.dima.unige.it. You may freely download
executable and documentation. You can also find a full list
of the platforms on which
CoCoA runs with instructions for installation, and information
regarding the system and associated research.
The CoCoA kernel is written in C (about 70,000 lines). It runs
on Linux, MacOS X, Microsoft Windows, and other platforms.
The accompanying library of packages, comprising around
17,000 lines of CoCoA language code, adds advanced capabilities
in other areas
such as statistics, integer programming, and invariant theory.
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