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authorPierrick-Dartois <pierrickdartois@icloud.com>2025-05-22 18:51:58 +0200
committerPierrick-Dartois <pierrickdartois@icloud.com>2025-05-22 18:51:58 +0200
commitcb6080eaa4f326d9fce5f0a9157be46e91d55e09 (patch)
tree4d080ade8db9faa0da5268ab420dad2b02a4e248 /theta_lib/theta_structures/Theta_dim4.py
parentd40de259097c5e8d8fd35539560ca7c3d47523e7 (diff)
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Clean up PEGASIS submodule inclusion
Diffstat (limited to 'theta_lib/theta_structures/Theta_dim4.py')
-rw-r--r--theta_lib/theta_structures/Theta_dim4.py351
1 files changed, 0 insertions, 351 deletions
diff --git a/theta_lib/theta_structures/Theta_dim4.py b/theta_lib/theta_structures/Theta_dim4.py
deleted file mode 100644
index 7851c56..0000000
--- a/theta_lib/theta_structures/Theta_dim4.py
+++ /dev/null
@@ -1,351 +0,0 @@
-from sage.all import *
-from sage.structure.element import get_coercion_model
-
-from .theta_helpers_dim4 import (
- hadamard,
- batch_inversion,
- product_theta_point_dim4,
- product_to_theta_points_dim4,
- product_theta_point_dim2_dim4,
- product_to_theta_points_dim4_dim2,
- act_point,
- squared,
-)
-from .Theta_dim1 import ThetaStructureDim1
-from .Tuple_point import TuplePoint
-from ..basis_change.base_change_dim4 import (
- apply_base_change_theta_dim4,
- random_symplectic_matrix,
- base_change_theta_dim4,
-)
-
-cm = get_coercion_model()
-
-
-class ThetaStructureDim4:
- def __init__(self,null_point,null_point_dual=None,inv_null_point_dual_sq=None):
- r"""
- INPUT:
- - null_point: theta-constants.
- - inv_null_point_dual_sq: inverse of the squares of dual theta-constants, if provided
- (meant to prevent duplicate computation, since this data is already computed when the
- codomain of an isogeny is computed).
- """
- if not len(null_point) == 16:
- raise ValueError("Entry null_point should have 16 coordinates.")
-
- self._base_ring = cm.common_parent(*(c.parent() for c in null_point))
- self._point = ThetaPointDim4
- self._null_point = self._point(self, null_point)
- self._null_point_dual=null_point_dual
- self._inv_null_point=None
- self._inv_null_point_dual_sq=inv_null_point_dual_sq
-
- def null_point(self):
- """
- """
- return self._null_point
-
- def null_point_dual(self):
- if self._null_point_dual==None:
- self._null_point_dual=hadamard(self._null_point.coords())
- return self._null_point_dual
-
- def base_ring(self):
- """
- """
- return self._base_ring
-
- def zero(self):
- """
- """
- return self.null_point()
-
- def zero_dual(self):
- return self.null_point_dual()
-
- def __repr__(self):
- return f"Theta structure over {self.base_ring()} with null point: {self.null_point()}"
-
- def __call__(self,coords):
- return self._point(self,coords)
-
- def act_null(self,I,J):
- r"""
- Point of 2-torsion.
-
- INPUT:
- - I, J: two 4-tuples of indices in {0,1}.
-
- OUTPUT: the action of (I,\chi_J) on the theta null point given by:
- (I,\chi_J)*P=(\chi_J(I+K)^{-1}P[I+K])_K
- """
- return self.null_point().act_point(I,J)
-
- def is_K2(self,B):
- r"""
- Given a symplectic decomposition A[2]=K_1\oplus K_2 canonically
- induced by the theta-null point, determines if B is the canonical
- basis of K_2 given by act_nul(0,\delta_i)_{1\leq i\leq 4}.
-
- INPUT:
- - B: Basis of 4 points of 2-torsion.
-
- OUTPUT: Boolean True if and only if B is the canonical basis of K_2.
- """
- I0=(0,0,0,0)
- if B[0]!=self.act_null(I0,(1,0,0,0)):
- return False
- if B[1]!=self.act_null(I0,(0,1,0,0)):
- return False
- if B[2]!=self.act_null(I0,(0,0,1,0)):
- return False
- if B[3]!=self.act_null(I0,(0,0,0,1)):
- return False
- return True
-
- def base_change_struct(self,N):
- null_coords=self.null_point().coords()
- new_null_coords=apply_base_change_theta_dim4(N,null_coords)
- return ThetaStructureDim4(new_null_coords)
-
- def base_change_coords(self,N,P):
- coords=P.coords()
- new_coords=apply_base_change_theta_dim4(N,coords)
- return self.__call__(new_coords)
-
- #@cached_method
- def _arithmetic_precomputation(self):
- r"""
- Initializes the precomputation containing the inverse of the theta-constants in standard
- and dual (Hadamard transformed) theta-coordinates. Assumes no theta-constant is zero.
- """
- O=self.null_point()
- if all([O[k]!=0 for k in range(16)]):
- self._inv_null_point=batch_inversion(O.coords())
- if self._inv_null_point_dual_sq==None:
- U_chi_0_sq=hadamard(squared(O.coords()))
- if all([U_chi_0_sq[k]!=0 for k in range(16)]):
- self._inv_null_point_dual_sq=batch_inversion(U_chi_0_sq)
- self._arith_base_change=False
- else:
- self._arith_base_change=True
- self._arithmetic_base_change()
- #print("Zero dual theta constants.\nRandom symplectic base change is being used for duplication.\nDoublings are more costly than expected.")
- else:
- self._arith_base_change=True
- self._arithmetic_base_change()
- #print("Zero theta constants.\nRandom symplectic base change is being used for duplication.\nDoublings are more costly than expected.")
-
- def _arithmetic_base_change(self,max_iter=50):
- F=self._base_ring
- if F.degree() == 2:
- i=self._base_ring.gen()
- else:
- assert(F.degree() == 1)
- Fp2 = GF((F.characteristic(), 2), name='i', modulus=var('x')**2 + 1)
- i=Fp2.gen()
-
- count=0
- O=self.null_point()
- while count<max_iter:
- count+=1
- M=random_symplectic_matrix(4)
- N=base_change_theta_dim4(M,i)
-
- NO=apply_base_change_theta_dim4(N,O)
- NU_chi_0_sq=hadamard(squared(NO))
-
- if all([NU_chi_0_sq[k]!=0 for k in range(16)]) and all([NO[k]!=0 for k in range(16)]):
- self._arith_base_change_matrix=N
- self._arith_base_change_matrix_inv=N.inverse()
- self._inv_null_point=batch_inversion(NO)
- self._inv_null_point_dual_sq=batch_inversion(NU_chi_0_sq)
- break
-
- def has_suitable_doubling(self):
- O=self.null_point()
- UO=hadamard(O.coords())
- if all([O[k]!=0 for k in range(16)]) and all([UO[k]!=0 for k in range(16)]):
- return True
- else:
- return False
-
- def hadamard(self):
- return ThetaStructureDim4(self.null_point_dual())
-
- def hadamard_change_coords(self,P):
- new_coords=hadamard(P)
- return self.__call__(new_coords)
-
-
-class ProductThetaStructureDim1To4(ThetaStructureDim4):
- def __init__(self,*args):
- r"""Defines the product theta structure at level 2 of 4 elliptic curves.
-
- Input: Either
- - 4 theta structures of dimension 1: T0, T1, T2, T3;
- - 4 elliptic curves: E0, E1, E2, E3.
- - 4 elliptic curves E0, E1, E2, E3 and their respective canonical 4-torsion basis B0, B1, B2, B3.
- """
- if len(args)==4:
- theta_structures=list(args)
- for k in range(4):
- if not isinstance(theta_structures[k],ThetaStructureDim1):
- try:
- theta_structures[k]=ThetaStructureDim1(theta_structures[k])
- except:
- pass
- elif len(args)==8:
- theta_structures=[ThetaStructureDim1(args[k],args[4+k][0],args[4+k][1]) for k in range(4)]
- else:
- raise ValueError("4 or 8 arguments expected but {} were given.\nYou should enter a list of 4 elliptic curves or ThetaStructureDim1\nor a list of 4 elliptic curves with a 4-torsion basis for each of them.".format(len(args)))
-
- self._theta_structures=theta_structures
-
- null_point=product_theta_point_dim4(theta_structures[0].zero().coords(),theta_structures[1].zero().coords(),
- theta_structures[2].zero().coords(),theta_structures[3].zero().coords())
-
- ThetaStructureDim4.__init__(self,null_point)
-
- def product_theta_point(self,theta_points):
- return self._point(self,product_theta_point_dim4(theta_points[0].coords(),theta_points[1].coords(),
- theta_points[2].coords(),theta_points[3].coords()))
-
- def __call__(self,point):
- if isinstance(point,TuplePoint):
- theta_points=[]
- theta_structures=self._theta_structures
- for i in range(4):
- theta_points.append(theta_structures[i](point[i]))
- return self.product_theta_point(theta_points)
- else:
- return self._point(self,point)
-
- def to_theta_points(self,P):
- theta_coords=product_to_theta_points_dim4(P)
- theta_points=[self._theta_structures[i](theta_coords[i]) for i in range(4)]
- return theta_points
-
- def to_tuple_point(self,P):
- theta_points=self.to_theta_points(P)
- montgomery_points=[self._theta_structures[i].to_montgomery_point(theta_points[i]) for i in range(4)]
- return TuplePoint(montgomery_points)
-
-class ProductThetaStructureDim2To4(ThetaStructureDim4):
- def __init__(self,theta1,theta2):
- self._theta_structures=(theta1,theta2)
-
- null_point=product_theta_point_dim2_dim4(theta1.zero().coords(),theta2.zero().coords())
-
- ThetaStructureDim4.__init__(self,null_point)
-
- def product_theta_point(self,P1,P2):
- return self._point(self,product_theta_point_dim2_dim4(P1.coords(),P2.coords()))
-
- def __call__(self,point):
- return self._point(self,point)
-
- def to_theta_points(self,P):
- theta_coords=product_to_theta_points_dim4_dim2(P)
- theta_points=[self._theta_structures[i](theta_coords[i]) for i in range(2)]
- return theta_points
-
-class ThetaPointDim4:
- def __init__(self, parent, coords):
- """
- """
- if not isinstance(parent, ThetaStructureDim4):
- raise ValueError("Entry parent should be a ThetaStructureDim4 object.")
-
- self._parent = parent
- self._coords = tuple(coords)
-
- def parent(self):
- """
- """
- return self._parent
-
- def theta(self):
- """
- """
- return self.parent()
-
- def coords(self):
- """
- """
- return self._coords
-
- def is_zero(self):
- """
- """
- return self == self.parent().zero()
-
- def __eq__(self, other):
- P=self.coords()
- Q=other.coords()
-
- k0=0
- while k0<15 and P[k0]==0:
- k0+=1
-
- for l in range(16):
- if P[l]*Q[k0]!=Q[l]*P[k0]:
- return False
- return True
-
- def __repr__(self):
- return f"Theta point with coordinates: {self.coords()}"
-
- def __getitem__(self,i):
- return self._coords[i]
-
- def scale(self,lamb):
- if lamb==0:
- raise ValueError("Entry lamb should be non-zero.")
-
- P=self.coords()
- return self._parent([lamb*x for x in P])
-
- def act_point(self,I,J):
- r"""
- Translation by a point of 2-torsion.
-
- Input:
- - I, J: two 4-tuples of indices in {0,1}.
-
- Output: the action of (I,\chi_J) on P given by:
- (I,\chi_J)*P=(\chi_J(I+K)^{-1}P[I+K])_K
- """
- return self._parent(act_point(self._coords,I,J))
-
- def double(self):
- ## This formula is projective.
- ## Works only when theta constants are non-zero.
- P=self.coords()
- if self.parent()._inv_null_point==None or self.parent()._inv_null_point_dual_sq==None:
- self.parent()._arithmetic_precomputation()
- inv_O,inv_U_chi_0_sq=self.parent()._inv_null_point,self.parent()._inv_null_point_dual_sq
-
- if self.parent()._arith_base_change:
- P=apply_base_change_theta_dim4(self.parent()._arith_base_change_matrix,P)
-
- U_chi_P=squared(hadamard(squared(P)))
- for chi in range(16):
- U_chi_P[chi]*=inv_U_chi_0_sq[chi]
-
- theta_2P = list(hadamard(U_chi_P))
- for i in range(16):
- theta_2P[i] *= inv_O[i]
-
- if self.parent()._arith_base_change:
- theta_2P=apply_base_change_theta_dim4(self.parent()._arith_base_change_matrix_inv,theta_2P)
-
- return self._parent(theta_2P)
-
- def double_iter(self,n):
- ## Computes 2**n*self
- Q=self
- for i in range(n):
- Q=Q.double()
- return Q