q3::SerialSubspaceDiagonalizer Class Reference

#include <serial.hpp>

Inheritance diagram for q3::SerialSubspaceDiagonalizer:

Public Member Functions
std::string	name () const override
int	solve (int basis_size, Complex *hamiltonian_matrix, Complex *overlap_matrix, Real *eigenvalues, Complex *eigenvector_matrix, bool is_gamma_only=false) override
Public Member Functions inherited from q3::SubspaceDiagonalizer
virtual	~SubspaceDiagonalizer ()=default
virtual bool	is_collective () const

Detailed Description

Definition at line 16 of file serial.hpp.

Member Function Documentation

name()

std::string q3::SerialSubspaceDiagonalizer::name ( ) const

inlineoverridevirtual

Implements q3::SubspaceDiagonalizer.

Definition at line 148 of file serial.hpp.

solve()

int q3::SerialSubspaceDiagonalizer::solve ( int  basis_size, Complex *  hamiltonian_matrix, Complex *  overlap_matrix, Real *  eigenvalues, Complex *  eigenvector_matrix, bool  is_gamma_only = false  )

inlineoverridevirtual

Solve the generalized eigenvalue problem: H * C = S * C * E

Parameters

basis_size	Dimension of the subspace (matrix size).
hamiltonian_matrix	Projected Hamiltonian (destroyed/overwritten). May be the same buffer as eigenvector_matrix: every implementation reads it whole before it writes any eigenvector, which is what lets the caller keep one copy of H rather than two.
overlap_matrix	Projected overlap (destroyed/overwritten).
eigenvalues	Output eigenvalues (size basis_size).
eigenvector_matrix	Output eigenvectors (basis_size x basis_size).

Returns

0 on success, non-zero on failure.

Gamma-only: H_sub and S_sub are real symmetric matrices, so dsygv solves them and its eigenvectors come out real.

Both are packed to real in place rather than into copies of their own: the real part of complex entry i is written to double entry i, which lies inside complex entry i/2 – already read – so a forward pass is safe, and the eigenvectors are expanded back to complex by a backward pass for the same reason. The matrices are the caller's to overwrite, and the Hamiltonian is usually the eigenvector buffer itself.

Non-gamma: use zhegv for complex Hermitian matrices. It leaves the eigenvectors where the Hamiltonian was, so the Hamiltonian goes into the eigenvector buffer – unless the caller already handed the same buffer as both.

Implements q3::SubspaceDiagonalizer.

Definition at line 18 of file serial.hpp.

References q3::lapack::dsygv_(), and q3::lapack::zhegv_().

---

The documentation for this class was generated from the following file:

• src/layer_4_computation/diagonalizer/planewave/subspace/serial.hpp