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changed deg() behaviour in Singular https://www.singular.uni-kl.de/forum/viewtopic.php?f=10&t=2540 |
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Author: | jakobkroeker [ Wed Jun 15, 2016 1:01 am ] |
Post subject: | changed deg() behaviour in Singular |
In Singular the behaviour of deg() changed between v3.1.7 and v 4.0.3. Question: - Which answer is correct ? - Which of the answers users really expected? Code: SINGULAR / Development A Computer Algebra System for Polynomial Computations / version 3-1-7 0< by: W. Decker, G.-M. Greuel, G. Pfister, H. Schoenemann \ Aug 2013 FB Mathematik der Universitaet, D-67653 Kaiserslautern \ // ** executing /run/media/jakob/TOEXT4/work/home_fc18/Projects/lipmanresolve/Singular-3-1-7/Singular/LIB/.singularrc > ring rng = 0,(x,y,z),dp; > . intmat im[3][3] = 3,0,1,1,1,0,1,0,0; > ring S = 0,(x,y,z),(M(im)); > S; // characteristic : 0 // number of vars : 3 // block 1 : ordering M // : names x y z // : weights 3 0 1 // : weights 1 1 0 // : weights 1 0 0 // block 2 : ordering C > poly p = x^3*y+x*z^4; > . deg(p); 9 > quit; Auf Wiedersehen. [jakob@vogon lipmanresolve]$ ./singular-spielwiese SINGULAR / Development A Computer Algebra System for Polynomial Computations / version 4.0.3 0< by: W. Decker, G.-M. Greuel, G. Pfister, H. Schoenemann \ Jan 2016 FB Mathematik der Universitaet, D-67653 Kaiserslautern \ // ** executing /run/media/jakob/TOEXT4/work/home_fc18/Projects/lipmanresolve/Singular-spielwiese/BUILD/Singular/LIB/.singularrc > ring rng = 0,(x,y,z),dp; > . intmat im[3][3] = 3,0,1,1,1,0,1,0,0; > ring S = 0,(x,y,z),(M(im)); > S; // characteristic : 0 // number of vars : 3 // block 1 : ordering M // : names x y z // : weights 3 0 1 // : weights 1 1 0 // : weights 1 0 0 // block 2 : ordering C > poly p = x^3*y+x*z^4; > . deg(p); 5 Remark: the changes also affects software which depends on Singular |
Author: | hannes [ Wed Jun 15, 2016 10:32 am ] |
Post subject: | Re: changed deg() behaviour in Singular |
deg(p) returns the maximal degree of all monomials in the polynomials with respect to the weights of the variables. The weights of the variables are derived from the ordering if the ordering is not a block ordering and if all weights are positive. Otherwise, the weights are 1. This is a result of the requirement that there are only finitely many monomials of the same degree (for non-blockorderings): it was not honored in 3-1. If you do not like this choice of weights, use Code: deg(p,w); where w is the weight vector of your choice. |
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