"Source: Text/Geometry/AlgSrf.text";
"Line: 2345";
"Date: Thu Sep 25 14:47:45 2025";
"Main: Fri Sep 26 14:29:19 2025";
// original file: Text/Geometry/AlgSrf.text, line: 2345
// Example: H126E11 ()
print "Example: H126E11";
ei := GetEchoInput();
SetEchoInput(true);
P4<x,y,z,t,u> := ProjectiveSpace(Rationals(),4);
S := Surface(P4,[z^2+x*t-y*t-z*u, x*z-y*z+x*u]);
dsds := ResolveSingularSurface(S);
#dsds;
B,F,w,div_dat := BasisOfHolomorphicTwoForms(S);
B; F;
w;
div_dat;
B := PluriCanonicalBasis(S,-1);
B;
// All elements of B are divisible by z-2u except the first.
// Change B[1] by an element of Ideal(S) to also give the divisibility.
B[1] := B[1]-(1/3)*(x*z - y*z + x*u);
B;
[b div (z-2*u) : b in B];
SetEchoInput(ei);
