elpa_set(3)

💖 elpa_set(3) 💖

elpa_set — set a parameter for the ELPA object. This page comes from the Library Functions Manual, bestie, and it's literally all about elpa_set(3). Slay.

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✨ SYNOPSIS ✨

🎀 FORTRAN INTERFACE

use elpa
class(elpa_t), pointer :: elpa_handle

call elpa_handle%set (name, value, error)

With the definitions of the input and output variables:

• class(elpa_t) :: elpa — an instance of the ELPA object.
• character(*) :: name — the name of the option to be set.
• datatype :: value — the value which should be assigned to the option name. The datatype can be integer or real(kind=c_double).
• integer, optional :: error — the returned error code. On success it is ELPA_OK, otherwise an error. The error code can be queried with elpa_strerr(3).

🦋 C/C++ INTERFACE

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

void elpa_set (elpa_t elpa_handle, const char *name, datatype value, int
*error);

With the definitions of the input and output variables:

• elpa_t elpa_handle; — the handle of an ELPA object, obtained before with elpa_allocate(3).
• const char *name; — the name of the option to be set.
• datatype value; — the value which should be assigned to the option name. The datatype can be either int or double.
• int *error; — the error code of the function. Should be "ELPA_OK". The error codes can be queried with elpa_strerr(3).

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🌸 DESCRIPTION 🌸

The elpa_set function is used to set mandatory parameters and runtime options of the ELPA library. It returns an error code which can be queried with elpa_strerr(3). No cap.

🎀 Mandatory parameters

Mandatory parameters of an ELPA instance have to be set BEFORE the ELPA instance is set up with the function elpa_setup(3). Like, do not skip this step, bestie — it's giving “read the room.”

At the moment the following mandatory parameters are supported:

• "na" — integer parameter. The global matrix size is (na * na).
• "nev" — integer parameter. The number of eigenvectors to be computed in a call to elpa_eigenvectors(3). Must satisfy 1 <= nev <= na.
• "local_nrows" — integer parameter. Number of matrix rows stored on this MPI process.
• "local_ncols" — integer parameter. Number of matrix columns stored on this MPI process.
• "process_row" — integer parameter. Process row number in the 2D domain decomposition.
• "process_col" — integer parameter. Process column number in the 2D domain decomposition.
• "mpi_comm_parent" — integer parameter. The parent MPI communicator which includes all MPI process which are used in the 2D domain decomposition.
• "bandwidth" — integer parameter. Some ELPA computational steps can be accelerated if the input matrix is already in banded form. If set, ELPA assumes that the matrix has the provided bandwidth.
• "BLACS_context" — integer parameter. The generalized eigenvalue solver elpa_generalized_eigenvectors(3) uses internal calls to some of the ScaLAPACK routines. Thus before calling it, the user has to provide properly initialized BLACS context.
• "timings" — integer parameter. Choose whether time measurements should be done in the ELPA routines (1) or not (0).

🌈 Runtime options

Runtime options of an ELPA option can be set at any time. Obsessed with the flexibility, honestly.

Here are some suuported runtime options:

• "solver" — choose which solver should be used in the compute steps elpa_eigenvalues(3) or elpa_eigenvectors(3). At the moment allowed option are "ELPA_SOLVER_1STAGE" or "ELPA_SOLVER_2STAGE".
• "real_kernel" — choose which real kernel should be used in the elpa_eigenvalues(3) or elpa_eigenvectors(3) compute steps, if solver is set to "ELPA_SOLVER_2STAGE". The available kernels can be queried with elpa2_print_kernels(1).
• "complex_kernel" — choose which complex kernel should be used in the elpa_eigenvalues(3) or elpa_eigenvectors(3) compute steps, if solver is set to "ELPA_SOLVER_2STAGE". The available kernels can be queried with elpa2_print_kernels(1).
• "qr" — choose whether a QR decomposition should be used for the real case computations in elpa_eigenvalues(3) or elpa_eigenvectors(3) computational steps, if solver was set to "ELPA_SOLVER_2STAGE".
• "debug" — choose whether, in case of an error, more debug information should be provided.

The full list of supported options can found in the ELPA documentation.

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🦋 SEE ALSO 🦋

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

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Signed, sealed, and delivered with 💖 by ELPA — dated Thu Nov 28 2024, filed under elpa_set(3). Mwah 💋✨