template<int SizeAtCompileTime, int MaxSizeAtCompileTime, typename _StorageIndex>
class Eigen::Transpositions< SizeAtCompileTime, MaxSizeAtCompileTime, _StorageIndex >
Represents a sequence of transpositions (row/column interchange)
- Template Parameters
-
SizeAtCompileTime | the number of transpositions, or Dynamic |
MaxSizeAtCompileTime | the maximum number of transpositions, or Dynamic. This optional parameter defaults to SizeAtCompileTime. Most of the time, you should not have to specify it. |
This class represents a permutation transformation as a sequence of n transpositions
. It is internally stored as a vector of integers indices
. Each transposition
applied on the left of a matrix (
) interchanges the rows i
and indices
[i] of the matrix M
. A transposition applied on the right (e.g.,
) yields a column interchange.
Compared to the class PermutationMatrix, such a sequence of transpositions is what is computed during a decomposition with pivoting, and it is faster when applying the permutation in-place.
To apply a sequence of transpositions to a matrix, simply use the operator * as in the following example:
MatrixXf mat;
mat = tr * mat;
Transpositions()
Definition: Transpositions.h:164
In this example, we detect that the matrix appears on both side, and so the transpositions are applied in-place without any temporary or extra copy.
- See also
- class PermutationMatrix