21745: fix quadratic_forms

Author: videlec

src/sage/quadratic_forms/quadratic_form__local_representation_conditions.py

@@ -607,7 +607,7 @@ def is_locally_represented_at_place(self, m, p):
         for s in sqclass:
             #print "m =", m, "   s =", s, "   m/s =", (QQ(m)/s)
             if (QQ(m)/s).is_padic_square(p):
-                nu = valuation(m//s, p)
+                nu = valuation(m/s, p)
                 return local_vec[sqclass.index(s) + 1] <= (nu / 2)
 
 

src/sage/quadratic_forms/quadratic_form__neighbors.py

@@ -214,7 +214,7 @@ def find_p_neighbor_from_vec(self, p, v):
     ## Lift the vector v to a vector v1 s.t. Q(v1) = 0 (mod p^2)
     s = self(v)
     if (s % p**2 != 0):
-        al = (-s / (p * vw_prod)) % p
+        al = (((-s // p) % p) * vw_prod.inverse_mod(p)) % p
         v1 = v + p * al * w
         v1w_prod = (v1 * self.matrix()).dot_product(w)
     else:
@@ -232,7 +232,7 @@ def find_p_neighbor_from_vec(self, p, v):
     good_basis = extend_to_primitive([v1, w])
     for i in range(2,n):
         ith_prod = (good_basis[i] * self.matrix()).dot_product(v)
-        c = (ith_prod / v1w_prod) % p
+        c = ((ith_prod % p) * v1w_prod.inverse_mod(p)) % p
         good_basis[i] = good_basis[i] - c * w  ## Ensures that this extension has <v_i, v> = 0 (mod p)
 
     ## DIAGNOSTIC

src/sage/quadratic_forms/ternary.pyx

@@ -1008,8 +1008,8 @@ def _find_p_neighbor_from_vec(a, b, c, r, s, t, p, v, mat = False):
 
     if m02%p!=0:
 
-        m0 = (-m00/m02/2) % p**2
-        m1 = (-m01/m02) % p
+        m0 = (((-m00//2) % p**2) * m02.inverse_mod(p**2)) % p**2
+        m1 = ((-m01 % p) * (m02.inverse_mod(p))) % p
 
         b00 = m0**2*m22/p**2 + 2*m0*m02/p**2 + m00/p**2
         b11 = m1**2*m22 + 2*m1*m12 + m11
@@ -1036,8 +1036,8 @@ def _find_p_neighbor_from_vec(a, b, c, r, s, t, p, v, mat = False):
 
     if m01%p!=0:
 
-        m0 = (-m00/m01/2) % p**2
-        m1 = (-m02/m01) % p
+        m0 = (((-m00//2) % p**2) * m01.inverse_mod(p**2)) % p**2
+        m1 = ((-m02 % p) * m01.inverse_mod(p)) % p
 
         b00 = m0**2*m11/p**2 + 2*m0*m01/p**2 + m00/p**2
         b11 = m1**2*m11 + 2*m1*m12 + m22

src/sage/quadratic_forms/ternary_qf.py

@@ -224,7 +224,8 @@ def __call__(self, v):
             ## Check if v has 3 cols
             if v.ncols() == 3:
                 M = v.transpose() * self.matrix() * v
-                return TernaryQF([M[0,0]//2, M[1,1]//2, M[2,2]//2, M[1,2], M[0,2], M[0,1]])
+                # NOTE: as soon as the deprecation from #21745 is over we can move the code below to a floordiv
+                return TernaryQF([(M[0,0]/2).floor(), (M[1,1]/2).floor(), (M[2,2]/2).floor(), M[1,2], M[0,2], M[0,1]])
             else:
                 return QuadraticForm(ZZ, v.transpose() * self.matrix() * v)
         elif (is_Vector(v) or isinstance(v, (list, tuple))):