def d2q2element(p: int, q: int, r: int, s: int, factor: Union[float, int])\
-> DualBasisElement:
"""
Build the dual basis element for symmetric form of 2-marginal
:param p: tensor index
:param q: tensor index
:param r: tensor index
:param s: tensor index
:param factor: scaling coeff for a symmetric constraint
:return: the dual basis of the mapping
"""
dbe = DualBasisElement()
dbe.add_element('cckk', (p, q, r, s), -1.0 * factor)
dbe.add_element('kkcc', (r, s, p, q), +1.0 * factor)
if q == s:
dbe.add_element('ck', (p, r), factor)
if p == r:
dbe.add_element('ck', (q, s), factor)
if q == r:
dbe.add_element('ck', (p, s), -1. * factor)
if p == s:
dbe.add_element('ck', (q, r), -1. * factor)
dbe.dual_scalar = (
kronecker_delta(q, s) * kronecker_delta(p, r) -
kronecker_delta(q, r) * kronecker_delta(p, s)) * factor
return dbe
def test_kronecker_delta_nonunit_args(self):
assert kronecker_delta(3, 3) == 1
def test_kronecker_delta_11(self):
assert kronecker_delta(1, 1) == 1
def test_kronecker_delta_10(self):
assert kronecker_delta(1, 0) == 0
def test_kronecker_delta_01(self):
assert kronecker_delta(0, 1) == 0
def test_kronecker_delta_00(self):
assert kronecker_delta(0, 0) == 1