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57.1 Introduction to grobner | ||
57.2 Functions and Variables for grobner |
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grobner
is a package for working with Groebner bases in Maxima.
To use the following functions you must load the `grobner.lisp' package.
load(grobner);
A demo can be started by
demo("grobner.demo");
or
batch("grobner.demo")
Some of the calculation in the demo will take a lot of time therefore the output `grobner-demo.output' of the demo can be found in the same directory as the demo file.
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The package was written by
Marek Rychlik
http://alamos.math.arizona.edu
and is released 2002-05-24 under the terms of the General Public License(GPL) (see file `grobner.lisp'). This documentation was extracted from the files
`README', `grobner.lisp', `grobner.demo', `grobner-demo.output'
by Günter Nowak. Suggestions for improvement of the documentation can be discussed at the maxima-mailing-list maxima@math.utexas.edu. The code is a little bit out of date now. Modern implementation use the fast F4 algorithm described in
A new efficient algorithm for computing Gröbner bases (F4) Jean-Charles Faugère LIP6/CNRS Université Paris VI January 20, 1999 |
Categories: Groebner bases Share packages Package grobner
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lex
pure lexicographic, default order for monomial comparisons
grlex
total degree order, ties broken by lexicographic
grevlex
total degree, ties broken by reverse lexicographic
invlex
inverse lexicographic order
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Default value: lex
This global switch controls which monomial order is used in polynomial and Groebner Bases calculations. If not set, lex
will be used.
Categories: Package grobner
Default value: expression_ring
This switch indicates the coefficient ring of the polynomials that
will be used in grobner calculations. If not set, maxima's general
expression ring will be used. This variable may be set to
ring_of_integers
if desired.
Categories: Package grobner
Default value: false
Name of the default order for eliminated variables in
elimination-based functions. If not set, lex
will be used.
Categories: Package grobner
Default value: false
Name of the default order for kept variables in elimination-based functions. If not set, lex
will be used.
Categories: Package grobner
Default value: false
Name of the default elimination order used in elimination
calculations. If set, it overrides the settings in variables
poly_primary_elimination_order
and poly_secondary_elimination_order
.
The user must ensure that this is a true elimination order valid
for the number of eliminated variables.
Categories: Package grobner
Default value: false
If set to true
, all functions in this package will return each
polynomial as a list of terms in the current monomial order rather
than a maxima general expression.
Categories: Package grobner
Default value: false
If set to true
, produce debugging and tracing output.
Categories: Package grobner
Default value: buchberger
Possible values:
buchberger
parallel_buchberger
gebauer_moeller
The name of the algorithm used to find the Groebner Bases.
Categories: Package grobner
Default value: false
If not false
, use top reduction only whenever possible. Top
reduction means that division algorithm stops after the first
reduction.
Categories: Package grobner
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poly_add
, poly_subtract
, poly_multiply
and poly_expt
are the arithmetical operations on polynomials.
These are performed using the internal representation, but the results are converted back to the
maxima general form.
Adds two polynomials poly1 and poly2.
(%i1) poly_add(z+x^2*y,x-z,[x,y,z]); 2 (%o1) x y + x
Categories: Package grobner
Subtracts a polynomial poly2 from poly1.
(%i1) poly_subtract(z+x^2*y,x-z,[x,y,z]); 2 (%o1) 2 z + x y - x
Categories: Package grobner
Returns the product of polynomials poly1 and poly2.
(%i2) poly_multiply(z+x^2*y,x-z,[x,y,z])-(z+x^2*y)*(x-z),expand; (%o1) 0
Categories: Package grobner
Returns the syzygy polynomial (S-polynomial) of two polynomials poly1 and poly2.
Categories: Package grobner
Returns the polynomial poly divided by the GCD of its coefficients.
(%i1) poly_primitive_part(35*y+21*x,[x,y]); (%o1) 5 y + 3 x
Categories: Package grobner
Returns the polynomial poly divided by the leading coefficient. It assumes that the division is possible, which may not always be the case in rings which are not fields.
Categories: Package grobner
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This function parses polynomials to internal form and back. It
is equivalent to expand(poly)
if poly parses correctly to
a polynomial. If the representation is not compatible with a
polynomial in variables varlist, the result is an error.
It can be used to test whether an expression correctly parses to the
internal representation. The following examples illustrate that
indexed and transcendental function variables are allowed.
(%i1) poly_expand((x-y)*(y+x),[x,y]); 2 2 (%o1) x - y (%i2) poly_expand((y+x)^2,[x,y]); 2 2 (%o2) y + 2 x y + x (%i3) poly_expand((y+x)^5,[x,y]); 5 4 2 3 3 2 4 5 (%o3) y + 5 x y + 10 x y + 10 x y + 5 x y + x (%i4) poly_expand(-1-x*exp(y)+x^2/sqrt(y),[x]); 2 y x (%o4) - x %e + ------- - 1 sqrt(y) (%i5) poly_expand(-1-sin(x)^2+sin(x),[sin(x)]); 2 (%o5) - sin (x) + sin(x) - 1
Categories: Package grobner
exponentitates poly by a positive integer number. If number is not a positive integer number an error will be raised.
(%i1) poly_expt(x-y,3,[x,y])-(x-y)^3,expand; (%o1) 0
Categories: Package grobner
poly_content
extracts the GCD of its coefficients
(%i1) poly_content(35*y+21*x,[x,y]); (%o1) 7
Categories: Package grobner
Pseudo-divide a polynomial poly by the list of n polynomials polylist. Return multiple values. The first value is a list of quotients a. The second value is the remainder r. The third argument is a scalar coefficient c, such that c*poly can be divided by polylist within the ring of coefficients, which is not necessarily a field. Finally, the fourth value is an integer count of the number of reductions performed. The resulting objects satisfy the equation:
c*poly=sum(a[i]*polylist[i],i=1...n)+r.
Categories: Package grobner
Divide a polynomial poly1 by another polynomial poly2. Assumes that exact division with no remainder is possible. Returns the quotient.
Categories: Package grobner
poly_normal_form
finds the normal form of a polynomial poly with respect
to a set of polynomials polylist.
Categories: Package grobner
Returns true
if polylist is a Groebner basis with respect to the current term
order, by using the Buchberger
criterion: for every two polynomials h1 and h2 in polylist the
S-polynomial S(h1,h2) reduces to 0 modulo polylist.
Categories: Package grobner
poly_buchberger
performs the Buchberger algorithm on a list of
polynomials and returns the resulting Groebner basis.
Categories: Package grobner
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The k-th elimination Ideal I_k of an Ideal I over K[ x[1],...,x[n] ] is the ideal intersect(I, K[ x[k+1],...,x[n] ]).
The colon ideal I:J is the ideal {h|for all w in J: w*h in I}.
The ideal I:p^inf is the ideal {h| there is a n in N: p^n*h in I}.
The ideal I:J^inf is the ideal {h| there is a n in N and a p in J: p^n*h in I}.
The radical ideal sqrt(I) is the ideal
{h| there is a n in N : h^n in I }.
poly_reduction
reduces a list of polynomials polylist, so that
each polynomial is fully reduced with respect to the other polynomials.
Categories: Package grobner
Returns a sublist of the polynomial list polylist spanning the same monomial ideal as polylist but minimal, i.e. no leading monomial of a polynomial in the sublist divides the leading monomial of another polynomial.
Categories: Package grobner
poly_normalize_list
applies poly_normalize
to each polynomial in the list.
That means it divides every polynomial in a list polylist by its leading coefficient.
Categories: Package grobner
Returns a Groebner basis of the ideal span by the polynomials polylist. Affected by the global flags.
Categories: Package grobner
Returns a reduced Groebner basis of the ideal span by the polynomials polylist. Affected by the global flags.
Categories: Package grobner
poly_depends
tests whether a polynomial depends on a variable var.
Categories: Package grobner Predicate functions
poly_elimination_ideal
returns the grobner basis of the number-th elimination ideal of an
ideal specified as a list of generating polynomials (not necessarily Groebner basis).
Categories: Package grobner
Returns the reduced Groebner basis of the colon ideal
I(polylist1):I(polylist2)
where polylist1 and polylist2 are two lists of polynomials.
Categories: Package grobner
poly_ideal_intersection
returns the intersection of two ideals.
Categories: Package grobner
Returns the lowest common multiple of poly1 and poly2.
Categories: Package grobner
Returns the greatest common divisor of poly1 and poly2.
See also ezgcd
,
gcd
,
gcdex
,
gcdivide
.
Example:
(%i1) p1:6*x^3+19*x^2+19*x+6; 3 2 (%o1) 6 x + 19 x + 19 x + 6 (%i2) p2:6*x^5+13*x^4+12*x^3+13*x^2+6*x; 5 4 3 2 (%o2) 6 x + 13 x + 12 x + 13 x + 6 x (%i3) poly_gcd(p1, p2, [x]); 2 (%o3) 6 x + 13 x + 6
Categories: Package grobner
poly_grobner_equal
tests whether two Groebner Bases generate the same ideal.
Returns true
if two lists of polynomials polylist1 and polylist2, assumed to be Groebner Bases,
generate the same ideal, and false
otherwise.
This is equivalent to checking that every polynomial of the first basis reduces to 0
modulo the second basis and vice versa. Note that in the example below the
first list is not a Groebner basis, and thus the result is false
.
(%i1) poly_grobner_equal([y+x,x-y],[x,y],[x,y]); (%o1) false
Categories: Package grobner
poly_grobner_subsetp
tests whether an ideal generated by polylist1
is contained in the ideal generated by polylist2. For this test to always succeed,
polylist2 must be a Groebner basis.
Categories: Package grobner Predicate functions
Returns true
if a polynomial poly belongs to the ideal generated by the
polynomial list polylist, which is assumed to be a Groebner basis. Returns false
otherwise.
poly_grobner_member
tests whether a polynomial belongs to an ideal generated by a list of polynomials,
which is assumed to be a Groebner basis. Equivalent to normal_form
being 0.
Categories: Package grobner
Returns the reduced Groebner basis of the saturation of the ideal
I(polylist):poly^inf
Geometrically, over an algebraically closed field, this is the set of polynomials in the ideal generated by polylist which do not identically vanish on the variety of poly.
Categories: Package grobner
Returns the reduced Groebner basis of the saturation of the ideal
I(polylist1):I(polylist2)^inf
Geometrically, over an algebraically closed field, this is the set of polynomials in the ideal generated by polylist1 which do not identically vanish on the variety of polylist2.
Categories: Package grobner
polylist2 ist a list of n polynomials [poly1,...,polyn]
.
Returns the reduced Groebner basis of the ideal
I(polylist):poly1^inf:...:polyn^inf
obtained by a sequence of successive saturations in the polynomials of the polynomial list polylist2 of the ideal generated by the polynomial list polylist1.
Categories: Package grobner
polylistlist is a list of n list of polynomials [polylist1,...,polylistn]
.
Returns the reduced Groebner basis of the saturation of the ideal
I(polylist):I(polylist_1)^inf:...:I(polylist_n)^inf
Categories: Package grobner
poly_saturation_extension
implements the famous Rabinowitz trick.
Categories: Package grobner
Categories: Package grobner
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