D.5.1.3 corank

Procedure from library classify.lib (see classify_lib).

Usage:

corank(f); f=poly

Return:

the corank of the Hessian matrix of f, of type int

Remark:

corank(f) is the number of variables occurring in the residual singularity after applying ’morsesplit’ to f

Example:

LIB "classify.lib";
ring r=0,(x,y,z),ds;
poly f=(x2+3y-2z)^2+xyz-(x-y3+x2*z3)^3;
corank(f);
→ 2