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USAGE: change_cost [options] groebner_file new_cost_file | ||
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DESCRIPTION: | ||
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change_cost is a program for recomputing the reduced Groebner basis of | ||
a toric ideal with respect to a term ordering with modified | ||
weights. This can be used for varying the cost function in integer | ||
programming (see the help for solve_IP for more information). | ||
The program simply restarts Buchberger�s algorithm on an already | ||
computed toric ideal using the modified term ordering. | ||
computed toric ideal using the modified term ordering. | ||
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FILE FORMAT: | ||
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The first input file has to be a GROEBNER file; the second input file | ||
should to be a NEW_COST file. For convenience, also MATRIX files are | ||
accepted as second input files. For their format see the help for the | ||
solve_IP or the toric_ideal program. | ||
solve_IP or the toric_ideal program. | ||
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change_cost writes the new Groebner basis into a GROEBNER file named | ||
like the second input file with extensions replaced by | ||
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.GB.<alg> | ||
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where GB stands for GROEBNER and <alg> is the abbreviation of the | ||
algorithm used for computing the input GROEBNER file (see the help for | ||
algorithm used for computing the input GROEBNER file (see the help for | ||
solve_IP or toric_ideal for an explaination). | ||
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A GROEBNER file looks as follows: | ||
GROEBNER | ||
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GROEBNER | ||
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computed with algorithm: | ||
<algorithm name abbreviation> (* abbreviations as above *) | ||
from file(s): (* the following four lines are | ||
from file(s): (* the following four lines are | ||
<name of respective MATRIX file> optional *) | ||
computation time: | ||
<computation time in seconds> | ||
computation time: | ||
<computation time in seconds> | ||
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term ordering: | ||
elimination block | ||
<number of elimination variables> | ||
<LEX / DEG_LEX (* only if number of elimination | ||
/ DEG_REV_LEX> variables >0 *) | ||
weighted block | ||
<number of weighted variables> | ||
<W_LEX / W_REV_LEX (* number of weighted variables | ||
<W_LEX / W_REV_LEX (* number of weighted variables | ||
/ W_DEG_LEX / W_DEG_REV_LEX> should always be >0 *) | ||
<weight_vector> | ||
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size: | ||
<number of elements> | ||
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Groebner basis: | ||
<basis elements> | ||
<settings for the Buchberger | ||
algorithm and compiler settings> (* optional *) | ||
<basis elements> | ||
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<settings for the Buchberger | ||
algorithm and compiler settings> (* optional *) | ||
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The Groebner basis consists always of binomials of the form x^a - x^b | ||
where x^a and x^b are relatively prime. Such a binomial can be | ||
represented by the vector a-b. The basis elements in the GROEBNER file | ||
represented by the vector a-b. The basis elements in the GROEBNER file | ||
are given by the coefficients of this vector representation. | ||
The settings for Buchberger�s algorithm and the compiler flags are | ||
produced when the GROEBNER file is generated by a call of solve_IP | ||
with the verbose output option | ||
-v, --verbose | ||
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-v, --verbose | ||
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Example: | ||
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GROEBNER | ||
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computed with algorithm: | ||
du | ||
term ordering: | ||
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term ordering: | ||
elimination block: | ||
0 | ||
weighted block: | ||
3 | ||
W_LEX | ||
1 2 3 | ||
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size: | ||
1 | ||
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Groebner basis: | ||
2 3 -2 (* x^2 * y^3 - z^2 *) | ||
2 3 -2 (* x^2 * y^3 - z^2 *) | ||
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A NEW_COST file should look as follows: | ||
NEW_COST | ||
variables: | ||
<number of weighted variables> | ||
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NEW_COST | ||
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variables: | ||
<number of weighted variables> | ||
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cost vector: | ||
<coefficients of the new weight vector> | ||
OPTIONS: | ||
<coefficients of the new weight vector> | ||
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OPTIONS: | ||
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-p <number> percentage of new generators to cause an | ||
autoreduction during Buchberger�s algorithm; | ||
autoreduction during Buchberger�s algorithm; | ||
<number> may be an arbitrary float, a | ||
negative value allows no intermediate | ||
autoreductions | ||
default is | ||
-p 12.0 | ||
default is | ||
-p 12.0 | ||
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-S [RP] [M] [B] [M] [2] criteria to use in Buchberger�s algorithm | ||
for discarding unneccessary S-pairs | ||
RP relatively prime leading terms | ||
M Gebauer-Moeller criterion M | ||
F Gebauer-Moeller criterion F | ||
B Gebauer-Moeller criterion B | ||
2 Buchberger�s second criterion | ||
default is | ||
-S RP M B | ||
-v, | ||
--verbose verbose output mode; writes the settings for | ||
default is | ||
-S RP M B | ||
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-v, | ||
--verbose verbose output mode; writes the settings for | ||
Buchberger�s algorithm and the compiler | ||
flags into the output GROEBNER file | ||
-V <number>, | ||
flags into the output GROEBNER file | ||
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-V <number>, | ||
--version <number> version of Buchberger�s algorithm to use; | ||
<number> may be 1, 1a, 2 or 3 | ||
default is | ||
-V 1 | ||
-V 1 | ||
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