Function EigensystemTridiagonal(bool, vector<double>&, vector<double>&, vector<double>&, vector<double>&)¶
Defined in File Lanczos.cpp
Function Documentation¶
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void EigensystemTridiagonal(bool evector_flag, vector<double> &alpha, vector<double> &beta, vector<double> &energy, vector<double> &evector)¶
From the Lanczos coefficients alpha and beta, returns the lowest eigenvalue and the corresponding eigenvector in the Lanczos (reduced) basis.
if evector_flag = false, calculates lowest eigenvalue only (no eigenvector); otherwise also calculates the associated eigenvector
- Parameters:
evector_flag – flag for the calculation of the eigenvector
alpha – Diagonal
beta – Second diagonal
energy – eigenvalues (not pre-allocated)
evector – lowest eigenvector in the reduced basis (not pre-allocated)