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)

Detailed Description

Chooses machine-dependent parameters for the local environment.

Function Documentation

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.