How to compute the max eigenvalue of one real matrix?

[wang__ningning]

How to compute the max eigenvalue of one real matrix? I only need the max eigenvalue, and best a function with fewer arguments in the calling sequence.

[Ruqiu_C_Intel]

Hello wang__ningning,

There are lots of functions to compute eigenvalue, for example ?sygvx can select eigenvalues by specifying either or range of indices for the desired eigenvalues. For more details please refer to the MKL developer reference: https://software.intel.com/content/www/us/en/develop/documentation/mkl-developer-reference-fortran/top/lapack-routines/lapack-least-squares-and-eigenvalue-problem-routines/lapack-least-squares-and-eigenvalue-problem-driver-routines/generalized-symmetric-definite-eigenvalue-problems-lapack-driver-routines/sygvx.html

Regards,

Ruqiu

[wang__ningning]

Yeah, I know there are many functions for Fortran 95 to compute the eigenvalue of real matrix. But in my test, the syevd is the most fast function than other functions, such as the sygvx, which can select eigenvalues.  So I want to konw which function is the most efficient to compute the eigenvalues?

[Ruqiu_C_Intel]

 Hello Wang_Ningning,

Have you checked this function below in the developer reference for computing the largest/smallest eigenvalues and corresponding eigenvectors of a standard eigenvalue problem:

mkl_sparse_?_ev (intel.com)

and set the first input parameter "which" as:

Indicates eigenvalues for which to search:

• which = 'L'

   indicates the largest eigenvalues.
• which = 'S'

   indicates the smallest eigenvalues.

[MRajesh_intel]

Hi,

Since we didn't hear back from you, we are closing this thread for now. If you require any additional assistance from Intel, please start a new thread. Any further interaction in this thread will be considered community only.

Have a Good day.

Regards

Rajesh