Changeset 99af0d in git

Timestamp:

Jul 8, 2010, 12:18:17 PM (13 years ago)

Author:

Hans Schoenemann <hannes@…>

Branches:

(u'jengelh-datetime', 'ceac47cbc86fe4a15902392bdbb9bd2ae0ea02c6')(u'spielwiese', 'f875bbaccd0831e36aaed09ff6adeb3eb45aeb94')

Children:

ba2be44979686110791931e4de45f3c9a46b1383

Parents:

9ae29ad7f27f9415c15371ba0d402a92043d4875

Message:

pfister: genus for char p

git-svn-id: file:///usr/local/Singular/svn/trunk@12955 2c84dea3-7e68-4137-9b89-c4e89433aadc

File:

• Singular/LIB/normal.lib (modified) (2 diffs)

Singular/LIB/normal.lib

@@ -2081 +2081 @@
 }
 ///////////////////////////////////////////////////////////////////////////////
+static proc deltaP(ideal I)
+{
+   def R=basering;
+   int c,d,i;
+   int n=nvars(R);
+   list nor;
+   if(size(I)>1){ERROR("no hypersurface");}
+   ideal J=std(slocus(I));
+   if(dim(J)<=0){return(0);}
+   poly h;
+   d=1;
+   while((d)&&(i<n))
+   {
+      i++;
+      h=var(i);
+      d=dim(std(J+ideal(h)));
+   }
+   i=0;
+   while(d)
+   {
+      i++;
+      if(i>10){ERROR("delta not found, please inform the authors")};
+      h=randomLast(100)[n];
+      d=dim(std(J+ideal(h)));
+   }
+   I=I,h-1;
+   if(char(R)<=19)
+   {
+      nor=normalP(I);
+   }
+   else
+   {
+      nor=normal(I);
+   }
+   return(nor[2][2]);
+}
 
 proc genus(ideal I,list #)
@@ -2101 +2137 @@
      def R1=changeord("dp");
      setring R1;
-     ideal J=std(imap(R0,I));
-     if(dim(J)!=1){ERROR("ideal defines not a curve");}
-     def S=changevar(varstr(R1)+",@t");
-     setring S;
-     ideal J=imap(R1,J);
-     J=std(homog(J,@t));
+     ideal I=imap(R0,I);
+     I=radical(I);
+     I=std(I);
+     if(dim(I)!=1)
+     {
+       if(((homog(I))&&(dim(I)!=2))||(!homog(I)))
+       {
+         ERROR("This is not a curve");
+       }
+     }
+     if(homog(I)&&(dim(I)==2))
+     {
+       def S=R0;
+       setring S;
+       ideal J=I;
+     }
+     else
+     {
+       def S=changevar(varstr(R0)+",@t");
+       setring S;
+       ideal J=imap(R1,I);
+       J=homog(J,@t);
+       J=std(J);
+     }
      int pa=1-hilbPoly(J)[1];
+     pa=pa-deltaP(J);
      setring R0;
-     if (char(basering)>7)
-     {
-       list nor=normal(I,"withDelta");
-       return(pa-nor[3][2]);
-     }
-     // only for very small char.:
-     list nor=normalP(I);
-     return(pa-nor[2][2]);
+     return(pa);
    }
    I=std(I);