sp_ienv.c File Reference

Chooses machine-dependent parameters for the local environment. More...

`#include "superlu_ddefs.h"`

`#include "machines.h"`

## Functions | |

int_t | sp_ienv_dist (int_t ispec) |

Chooses machine-dependent parameters for the local environment.

int_t sp_ienv_dist | ( | int_t | ispec | ) |

## Purpose

sp_ienv_dist() is inquired to choose machine-dependent parameters for the local environment. See ISPEC for a description of the parameters.

This version provides a set of parameters which should give good, but not optimal, performance on many of the currently available computers. Users are encouraged to modify this subroutine to set the tuning parameters for their particular machine using the option and problem size information in the arguments.

## Arguments

ISPEC (input) int Specifies the parameter to be returned as the value of SP_IENV_DIST. = 1: the panel size w; a panel consists of w consecutive columns of matrix A in the process of Gaussian elimination. The best value depends on machine's cache characters. = 2: the relaxation parameter relax; if the number of nodes (columns) in a subtree of the elimination tree is less than relax, this subtree is considered as one supernode, regardless of the their row structures. = 3: the maximum size for a supernode, which must be greater than or equal to relaxation parameter (see case 2); = 4: the minimum row dimension for 2-D blocking to be used; = 5: the minimum column dimension for 2-D blocking to be used; = 6: the estimated fills factor for the adjacency structures of L and U, compared with A;

(SP_IENV_DIST) (output) int >= 0: the value of the parameter specified by ISPEC < 0: if SP_IENV_DIST = -k, the k-th argument had an illegal value.

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