elpa_eigenvectors_float(3)

💖 NAME 💖

Okay so bestie, this is elpa_eigenvectors_float(3) from the Library Functions Manual, and it computes all eigenvalues and (part of) the eigenvectors for a real symmetric eigenproblem: A*Q = λ*Q 💅✨

🌸 SYNOPSIS 🌸

🎀 FORTRAN INTERFACE 🎀

use elpa
class(elpa_t), pointer :: elpa_handle

call elpa_handle%eigenvectors_float (a, ev, q, error)

With the definitions of the input and output variables:

• class(elpa_t) :: elpa_handle — An instance of the ELPA object. Your main character handle, fr fr 👑
• real(kind=c_float) :: a OR type(c_ptr) :: a — The local part of the host/device matrix A for which all eigenvalues and (part of) eigenvectors should be computed. The dimensions of matrix a must be set BEFORE with the methods elpa_set(3) and elpa_setup(3). The global matrix has to be symmetric, this is not checked by the routine 😭. In case of a GPU build a can be a pointer to the device memory.
• real(kind=c_float) :: ev OR type(c_ptr) :: ev — The host/device vector ev where the eigenvalues will be stored in ascending order. In case of a GPU build ev can be a pointer to the device memory.
• real(kind=c_float) :: q OR type(c_ptr) :: q — The host/device storage space for the computed eigenvectors. The number of requested eigenvectors must be set BEFORE with the methods elpa_set(3) and elpa_setup(3). In case of a GPU build q can be a pointer to the device memory.
• integer, optional :: error — The return error code of the function. Should be "ELPA_OK". The error code can be queried with the function elpa_strerr(3) 🫶

💻 C/C++ INTERFACE 💻

#include <elpa/elpa.h>
elpa_t elpa_handle;

void elpa_eigenvectors_float(elpa_t elpa_handle, float *a, float *ev,
       float *q, int *error);

With the definitions of the input and output variables:

• elpa_t elpa_handle; — The handle to the ELPA object 👑
• float *a; — The local part of the host/device matrix A for which the eigenpairs should be computed. The dimensions of the matrix must be set BEFORE with the methods elpa_set(3) and elpa_setup(3). The global matrix has to be symmetric, this is not checked by the routine 😭. In case of a GPU build a can be a pointer to the device memory.
• float *ev; — The host/device storage for the computed eigenvalues. Eigenvalues will be stored in ascending order. In case of a GPU build ev can be a pointer to the device memory.
• float *q; — The host/device storage space for the computed eigenvectors. The number of requested eigenvectors must be set BEFORE with the methods elpa_set(3) and elpa_setup(3). In case of a GPU build q can be a pointer to the device memory.
• int *error; — The error code of the function. Should be "ELPA_OK". The error codes can be queried with elpa_strerr(3) 🫶

✨ DESCRIPTION ✨

Okay so listen — this computes the eigenvalues and (part of) the eigenvectors of a real symmetric matrix. The functions elpa_init(3), elpa_allocate(3), elpa_set(3), and elpa_setup(3) must be called BEFORE elpa_eigenvectors_float can be called. In particular, the number of eigenvectors to be computed, "nev", must be set with elpa_set(3) ⭐

No cap: the global matrix has to be symmetric, and this routine does not check that for you. So don't come for this function if the matrix is giving chaos 💀

🦋 SEE ALSO 🦋

Go give these besties a read, iykyk 💖

• elpa2_print_kernels(1)
• elpa_init(3)
• elpa_allocate(3)
• elpa_set(3)
• elpa_setup(3)
• elpa_strerr(3)
• elpa_eigenvalues(3)
• elpa_skew_eigenvalues(3)
• elpa_skew_eigenvectors(3)
• elpa_cholesky(3)
• elpa_invert_triangular(3)
• elpa_solve_tridiagonal(3)
• elpa_hermitian_multiply(3)
• elpa_uninit(3)
• elpa_deallocate(3)

This iconic page came from ELPA, dated Thu Nov 28 2024, and it's literally elpa_eigenvectors_float(3) — periodt. 💅✨🎀