Singular Manual: modGB

| #### D.4.17.2 modGB Procedure from library `modstd.lib` (see modstd_lib). Usage: modGB(method, I[, exactness]); I ideal/module, exactness int method can be: std, slimgb, sba Return: a standard basis of I Note: The procedure computes a standard basis of I (over the rational numbers) by using modular methods. An optional parameter 'exactness' can be provided. If exactness = 1(default), the procedure computes a standard basis of I for sure; if exactness = 0, it computes a standard basis of I with high probability. Example:
    LIB "modstd.lib";
    ring R1 = 0, (x,y,z,t), dp;
    ideal I = 3x3+x2+1, 11y5+y3+2, 5z4+z2+4;
    ideal J = modGB("slimgb",I);
    J;
    ==> J[1]=x3+1/3x2+1/3
    ==> J[2]=z4+1/5z2+4/5
    ==> J[3]=y5+1/11y3+2/11
    I = homog(I, t);
    J = modGB("slimgb",I);
    J;
    ==> J[1]=x3+1/3x2t+1/3t3
    ==> J[2]=z4+1/5z2t2+4/5t4
    ==> J[3]=y5+1/11y3t2+2/11t5
    ring R3 = 0, x(1..4), lp;
    ideal I = cyclic(4);
    ideal J1 = modGB("slimgb",I, 1);   // default
    ideal J2 = modGB("slimgb",I, 0);
    size(reduce(J1, J2));
    ==> 0
    size(reduce(J2, J1));
    ==> 0
See also: modular.

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