- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content

Hello,

I am currently trying to solve the eigenproblem **Av** = λ**v** where A is a complex hermitian matrix using the MKL feast implementation. For testing purposes I constructed the following example (using C++):

#include <mkl.h> #include <iostream> #include <vector> #include <complex> int main() { using namespace std; int fpm[128]{ }; ::feastinit(fpm); /* A = 0 2-i 1 2+i 0 0 1 0 0 */ vector<complex<double>> entries = { complex<double>(2, -1), 1, complex<double>(2, +1), 1 }; vector<int> cols = { 2, 3, 1, 1 }; vector<int> rows = { 1, 3, 4, 5 }; char uplo = 'F'; double eps = 0; int loop = 0; double emin = -4; double emax = 4; int m0 = 3; vector<complex<double>> eigenvectors(m0 * m0); vector<double> eigenvalues(m0); vector<double> res(m0); int mode = 0; int info = 0; zfeast_hcsrev(&uplo, &m0, reinterpret_cast<MKL_Complex16*>(&entries[0]), &rows[0], &cols[0], fpm, &eps, &loop, &emin, &emax, &m0, &eigenvalues[0], reinterpret_cast<MKL_Complex16*>(&eigenvectors[0]), &mode, &res[0], &info); }

The eigenvalues of the matrix are 0 and ±square root 6 ≈ ±2.44948.

MKL produces this exact eigenvalues. However, the eigenvectos are strange. For example, the corresponding eigenvector for +sqrt(6) is (already normalized):

1/sqrt(2), 1/sqrt(2) + i/(2*sqrt(3)), 1/(2*sqrt(3))

or alternatively

0.707106, 0.577350 + i*0.28867, 0.28867

However, MKL produces:

0.48890728596802574+i*0.51085190195141617

0.19063671173166902+i*0.61670439499553087

0.19959556369177356+i*0.20855441565187854

What's the matter with these? What am I doing wrong?

Thank you.

Link Copied

- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Printer Friendly Page