def compute_norm(self, field=None, **defaults_config):
'''
Proves ‖a ⊗ b ⊗ ... ⊗ y ⊗ z‖ = ‖a‖·‖b‖·...·‖y‖·‖z‖.
'''
from proveit.logic import EvaluationError
from . import norm_of_tensor_prod, norm_preserving_tensor_prod
_a = self.operands
_i = _a.num_elements()
_K = VecSpaces.get_field(field)
vec_spaces = VecSpaces.known_vec_spaces(self.operands, field=_K)
# See if all of the operand normalizations evaluate to one.
all_norm_one = True
try:
for operand in self.operands:
if isinstance(operand, ExprRange):
with defaults.temporary() as tmp_defaults:
tmp_defaults.assumptions = defaults.assumptions + (
operand.parameter_condition(),)
body_norm = operand.body.compute_norm()
if body_norm.rhs.evaluated() != one:
all_norm_one = False
break
else:
if operand.compute_norm().rhs.evaluated() != one:
all_norm_one = False
break
except (EvaluationError, NotImplementedError):
all_norm_one = False
pass
if all_norm_one:
thm = norm_preserving_tensor_prod
else:
thm = norm_of_tensor_prod
return thm.instantiate({K: _K, i: _i, V: vec_spaces, a: _a})
def deduce_in_vec_space(self, vec_space=None, *, field,
**defaults_config):
'''
Deduce that the tensor product of vectors is in a vector space
which is the tensor product of corresponding vectors spaces.
'''
from . import tensor_prod_is_in_tensor_prod_space
_a = self.operands
_i = _a.num_elements()
_K = VecSpaces.get_field(field)
vec_spaces = VecSpaces.known_vec_spaces(self.operands, field=_K)
membership = tensor_prod_is_in_tensor_prod_space.instantiate(
{K: _K, i: _i, V: vec_spaces, a: _a})
if vec_space is not None and membership.domain != vec_space:
sub_rel = SubsetEq(membership.domain, vec_space)
return sub_rel.derive_superset_membership(self)
return membership