如何为 Eigen::EigenSolver 使用 Eigen::Map 对象？

Question

我有一个连续的 OpenCV（非对称）矩阵 cv::Mat m，我想通过 Eigen::EigenSolver 计算它的特征向量和特征值。

由于 m 可能很大，通过 cv2eigen 函数复制是低效的。然后，我想用Eigen::Map。这是我的代码：

Eigen::Map<Eigen::Matrix<float, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>> mMapped (m.ptr<float>(), m.rows, m.cols);
Eigen::EigenSolver<Eigen::Map<Eigen::Matrix<float, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>>> solver(mMapped,true);//this gives a bunch of errors

最后一行给出了一堆错误（见题尾）。我该如何解决这个问题？请注意，我应该避免将 mMapped 复制到矩阵对象，否则它等同于使用 cv2eigen（我认为）。

/usr/local/include/eigen3/Eigen/src/Eigenvalues/EigenSolver.h: In instantiation of ‘class Eigen::EigenSolver<Eigen::Map<Eigen::Matrix<float, -1, -1, 1> > >’:
../Math.hpp:64:104:   required from ‘static void Math::createHashTable(const cv::Mat&, cv::Mat&, cv::Mat&, int, int) [with T = float]’
../CloudCache.cpp:155:58:   required from here
/usr/local/include/eigen3/Eigen/src/Eigenvalues/EigenSolver.h:71:10: error: ‘Options’ is not a member of ‘Eigen::EigenSolver<Eigen::Map<Eigen::Matrix<float, -1, -1, 1> > >::MatrixType {aka Eigen::Map<Eigen::Matrix<float, -1, -1, 1> >}’
     enum {
          ^
In file included from /usr/local/include/eigen3/Eigen/Eigenvalues:29:0,
                 from ../Math.hpp:16,
                 from ../CloudCache.cpp:15:
/usr/local/include/eigen3/Eigen/src/Eigenvalues/RealSchur.h: In instantiation of ‘class Eigen::RealSchur<Eigen::Map<Eigen::Matrix<float, -1, -1, 1> > >’:
/usr/local/include/eigen3/Eigen/src/Eigenvalues/EigenSolver.h:312:27:   required from ‘class Eigen::EigenSolver<Eigen::Map<Eigen::Matrix<float, -1, -1, 1> > >’
../Math.hpp:64:104:   required from ‘static void Math::createHashTable(const cv::Mat&, cv::Mat&, cv::Mat&, int, int) [with T = float]’
../CloudCache.cpp:155:58:   required from here
/usr/local/include/eigen3/Eigen/src/Eigenvalues/RealSchur.h:58:10: error: ‘Options’ is not a member of ‘Eigen::RealSchur<Eigen::Map<Eigen::Matrix<float, -1, -1, 1> > >::MatrixType {aka Eigen::Map<Eigen::Matrix<float, -1, -1, 1> >}’
     enum {
          ^
In file included from /usr/local/include/eigen3/Eigen/src/Eigenvalues/RealSchur.h:14:0,
                 from /usr/local/include/eigen3/Eigen/Eigenvalues:29,
                 from ../Math.hpp:16,
                 from ../CloudCache.cpp:15:
/usr/local/include/eigen3/Eigen/src/Eigenvalues/HessenbergDecomposition.h: In instantiation of ‘class Eigen::HessenbergDecomposition<Eigen::Map<Eigen::Matrix<float, -1, -1, 1> > >’:
/usr/local/include/eigen3/Eigen/src/Eigenvalues/RealSchur.h:228:41:   required from ‘class Eigen::RealSchur<Eigen::Map<Eigen::Matrix<float, -1, -1, 1> > >’
/usr/local/include/eigen3/Eigen/src/Eigenvalues/EigenSolver.h:312:27:   required from ‘class Eigen::EigenSolver<Eigen::Map<Eigen::Matrix<float, -1, -1, 1> > >’
../Math.hpp:64:104:   required from ‘static void Math::createHashTable(const cv::Mat&, cv::Mat&, cv::Mat&, int, int) [with T = float]’
../CloudCache.cpp:155:58:   required from here
/usr/local/include/eigen3/Eigen/src/Eigenvalues/HessenbergDecomposition.h:64:10: error: ‘Options’ is not a member of ‘Eigen::HessenbergDecomposition<Eigen::Map<Eigen::Matrix<float, -1, -1, 1> > >::MatrixType {aka Eigen::Map<Eigen::Matrix<float, -1, -1, 1> >}’
     enum {
          ^
subdir.mk:30: recipe for target 'CloudCache.o' failed
make: *** [CloudCache.o] Error 1

Answer 1

您不能用 Map 声明 EigenSolver，矩阵类型必须是 Matrix，因此在您的情况下：

typedef Matrix<float,Dynamic,Dynamic,RowMajor> RowMatrixXf;
Map<RowMatrixXf> mMapped (m.ptr<float>(), m.rows, m.cols);
EigenSolver<MatrixXf> eig(mMapped);

您也可以用 RowMatrixXf 实例化 EigenSolver，但尽管进行了换位，性能还是会降低。

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