perms.perm_sign
¶
Calculate permutation sign.
Module Contents¶
Functions¶
|
Compute the "sign" of a permutation [1]. |
- perms.perm_sign.perm_sign(perm)¶
Compute the “sign” of a permutation [1].
The sign (either -1 or 1) of the permutation
perm
is-1**`inv
, whereinv
is the number of inversions contained inperm
.Examples
For the following vector
\[[1, 2, 3, 4]\]the permutation sign is positive as the number of elements in the vector are even. This can be performed in
toqito
as follows.>>> from toqito.perms import perm_sign >>> perm_sign([1, 2, 3, 4]) 1.0
For the following vector
\[[1, 2, 3, 4, 5]\]the permutation sign is negative as the number of elements in the vector are odd. This can be performed in
toqito
as follows.>>> from toqito.perms import perm_sign >>> perm_sign([1, 2, 4, 3, 5]) -1.0
References
- Parameters:
perm (numpy.ndarray | list[int]) – The permutation vector to be checked.
- Returns:
The value 1 if the permutation is of even length and the value of -1 if the permutation is of odd length.
- Return type:
float