Singular Manual: nrRootsProbab

| #### D.12.7.1 nrRootsProbab Procedure from library `rootsmr.lib` (see rootsmr_lib). Return: int: the number of real roots of the ideal I by a probabilistic algorithm Assume: If I is not a Groebner basis, then a Groebner basis will be computed by using std. If I is already a Groebner basis (i.e. if attrib(I,"isSB"); returns 1) then this Groebner basis will be used, hence it must be one w.r.t. (any) global ordering. This may be useful if the ideal is known to be a Groebner basis or if it can be computed faster by a different method. Note: If n<10 is given, n is the number of digits being used for constructing a random characteristic polynomial, a bigger n is more safe but slower (default: n=5). If printlevel>0 the number of complex solutions is displayed (default: printlevel=0). Example:
    LIB "rootsmr.lib";
    ring r = 0,(x,y,z),lp;
    ideal i = (x-1)*(x-2),(y-1)^3*(x-y),(z-1)*(z-2)*(z-3)^2;
    nrRootsProbab(i);       //no of real roots (using internally std)
    ==> 9
    i = groebner(i);        //using the hilbert driven GB computation
    int pr = printlevel;
    printlevel = 2;
    nrRootsProbab(i);
    ==> //ideal has 32 complex solutions, counted with multiplicity
    ==> *********************************************************************
    ==> * WARNING: This polynomial was obtained using  pseudorandom numbers.*
    ==> * If you want to verify the result, please use the command          *
    ==> *                                                                   *
    ==> * verify(p,b,i)                                                     *
    ==> *                                                                   *
    ==> * where p is the polynomial I returned, b is the monomial basis     *
    ==> * used, and i the Groebner basis of the ideal                       *
    ==> *********************************************************************
    ==> 9
    printlevel = pr;
See also: nrRootsDeterm; nrroots; randcharpoly; solve.

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