Current File : //proc/thread-self/root/usr/lib/python3/dist-packages/sympy/matrices/expressions/matpow.py
from sympy.matrices.common import NonSquareMatrixError
from .matexpr import MatrixExpr
from .special import Identity
from sympy.core import S
from sympy.core.sympify import _sympify
from sympy.matrices import MatrixBase
class MatPow(MatrixExpr):
def __new__(cls, base, exp, evaluate=False, **options):
base = _sympify(base)
if not base.is_Matrix:
raise TypeError("MatPow base should be a matrix")
if not base.is_square:
raise NonSquareMatrixError("Power of non-square matrix %s" % base)
exp = _sympify(exp)
obj = super().__new__(cls, base, exp)
if evaluate:
obj = obj.doit(deep=False)
return obj
@property
def base(self):
return self.args[0]
@property
def exp(self):
return self.args[1]
@property
def shape(self):
return self.base.shape
def _entry(self, i, j, **kwargs):
from sympy.matrices.expressions import MatMul
A = self.doit()
if isinstance(A, MatPow):
# We still have a MatPow, make an explicit MatMul out of it.
if A.exp.is_Integer and A.exp.is_positive:
A = MatMul(*[A.base for k in range(A.exp)])
#elif A.exp.is_Integer and self.exp.is_negative:
# Note: possible future improvement: in principle we can take
# positive powers of the inverse, but carefully avoid recursion,
# perhaps by adding `_entry` to Inverse (as it is our subclass).
# T = A.base.as_explicit().inverse()
# A = MatMul(*[T for k in range(-A.exp)])
else:
# Leave the expression unevaluated:
from sympy.matrices.expressions.matexpr import MatrixElement
return MatrixElement(self, i, j)
return A[i, j]
def doit(self, **kwargs):
if kwargs.get('deep', True):
base, exp = [arg.doit(**kwargs) for arg in self.args]
else:
base, exp = self.args
# combine all powers, e.g. (A ** 2) ** 3 -> A ** 6
while isinstance(base, MatPow):
exp *= base.args[1]
base = base.args[0]
if isinstance(base, MatrixBase):
# Delegate
return base ** exp
# Handle simple cases so that _eval_power() in MatrixExpr sub-classes can ignore them
if exp == S.One:
return base
if exp == S.Zero:
return Identity(base.rows)
if exp == S.NegativeOne:
from sympy.matrices.expressions import Inverse
return Inverse(base).doit(**kwargs)
eval_power = getattr(base, '_eval_power', None)
if eval_power is not None:
return eval_power(exp)
return MatPow(base, exp)
def _eval_transpose(self):
base, exp = self.args
return MatPow(base.T, exp)
def _eval_derivative(self, x):
from sympy import Pow
return Pow._eval_derivative(self, x)
def _eval_derivative_matrix_lines(self, x):
from sympy.core.expr import ExprBuilder
from sympy.tensor.array.expressions.array_expressions import ArrayContraction
from ...tensor.array.expressions.array_expressions import ArrayTensorProduct
from .matmul import MatMul
from .inverse import Inverse
exp = self.exp
if self.base.shape == (1, 1) and not exp.has(x):
lr = self.base._eval_derivative_matrix_lines(x)
for i in lr:
subexpr = ExprBuilder(
ArrayContraction,
[
ExprBuilder(
ArrayTensorProduct,
[
Identity(1),
i._lines[0],
exp*self.base**(exp-1),
i._lines[1],
Identity(1),
]
),
(0, 3, 4), (5, 7, 8)
],
validator=ArrayContraction._validate
)
i._first_pointer_parent = subexpr.args[0].args
i._first_pointer_index = 0
i._second_pointer_parent = subexpr.args[0].args
i._second_pointer_index = 4
i._lines = [subexpr]
return lr
if (exp > 0) == True:
newexpr = MatMul.fromiter([self.base for i in range(exp)])
elif (exp == -1) == True:
return Inverse(self.base)._eval_derivative_matrix_lines(x)
elif (exp < 0) == True:
newexpr = MatMul.fromiter([Inverse(self.base) for i in range(-exp)])
elif (exp == 0) == True:
return self.doit()._eval_derivative_matrix_lines(x)
else:
raise NotImplementedError("cannot evaluate %s derived by %s" % (self, x))
return newexpr._eval_derivative_matrix_lines(x)
def _eval_inverse(self):
return MatPow(self.base, -self.exp)
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