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Topic review - Vector space basis of the quotient of two ideals |
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To compute only the dimension, codim (from sing.lib) is probably the fastest. To compute a basis you can use modulo. Here is an example: Code: LIB"sing.lib"; ring r = 0,x(1..4),dp; int k=4; ideal i = sparseid(3,2,k-1,50,10); //create a random sparse ideal ideal m1 = maxideal(k); attrib(m1,"isSB",1); i = intersect(m1,i); //not necessary for modulo ideal m2 = maxideal(k+1),i; m2 = std(m2); //not necessary for modulo codim(m1,m2); //computes the dimension module m = std(modulo(m1,m2)); vdim(m); //same as codim(m1,m2) but //with a different algorithm matrix K = matrix(kbase(m)); matrix M1 = matrix(m1); ideal B = M1*K; //the basis of m1/m2
For increasing k use a k-loop. Note that maxideal(k) will become rather big, hence this will work only for small k (depending on I).
To compute only the dimension, codim (from sing.lib) is probably the fastest. To compute a basis you can use modulo. Here is an example:
[code] LIB"sing.lib"; ring r = 0,x(1..4),dp; int k=4; ideal i = sparseid(3,2,k-1,50,10); //create a random sparse ideal ideal m1 = maxideal(k); attrib(m1,"isSB",1); i = intersect(m1,i); //not necessary for modulo ideal m2 = maxideal(k+1),i; m2 = std(m2); //not necessary for modulo codim(m1,m2); //computes the dimension module m = std(modulo(m1,m2)); vdim(m); //same as codim(m1,m2) but //with a different algorithm matrix K = matrix(kbase(m)); matrix M1 = matrix(m1); ideal B = M1*K; //the basis of m1/m2 [/code]
For increasing k use a k-loop. Note that maxideal(k) will become rather big, hence this will work only for small k (depending on I).
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Posted: Wed Nov 19, 2008 12:36 am |
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Vector space basis of the quotient of two ideals |
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How can I compute a vector space basis of the quotient of two ideals using SINGULAR? For example, let m be a maximal ideal and I an arbitrary ideal in k[x_1,...,x_n]. I would like to compute a basis of m^k / (m^{k+1} + I) for increasing k.
How can I compute a vector space basis of the quotient of two ideals using SINGULAR? For example, let m be a maximal ideal and I an arbitrary ideal in k[x_1,...,x_n]. I would like to compute a basis of m^k / (m^{k+1} + I) for increasing k.
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Posted: Wed Nov 19, 2008 12:35 am |
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