spivotL.c File Reference

Performs numerical pivoting. More...

#include <math.h>
#include <stdlib.h>
#include "slu_sdefs.h"

Include dependency graph for spivotL.c:

Functions
int	spivotL (const int jcol, const double u, int *usepr, int *perm_r, int *iperm_r, int *iperm_c, int *pivrow, GlobalLU_t *Glu, SuperLUStat_t *stat)

Detailed Description

Copyright (c) 2003, The Regents of the University of California, through Lawrence Berkeley National Laboratory (subject to receipt of any required approvals from U.S. Dept. of Energy)

All rights reserved.

The source code is distributed under BSD license, see the file License.txt at the top-level directory.

– SuperLU routine (version 3.0) –
Univ. of California Berkeley, Xerox Palo Alto Research Center,
and Lawrence Berkeley National Lab.
October 15, 2003

Copyright (c) 1994 by Xerox Corporation.  All rights reserved.

THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY
EXPRESSED OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.

Permission is hereby granted to use or copy this program for any
purpose, provided the above notices are retained on all copies.
Permission to modify the code and to distribute modified code is
granted, provided the above notices are retained, and a notice that
the code was modified is included with the above copyright notice.

Function Documentation

int spivotL	(	const int	jcol,
		const double	u,
		int *	usepr,
		int *	perm_r,
		int *	iperm_r,
		int *	iperm_c,
		int *	pivrow,
		GlobalLU_t *	Glu,
		SuperLUStat_t *	stat
	)

Purpose

  Performs the numerical pivoting on the current column of L,
  and the CDIV operation.

  Pivot policy:
  (1) Compute thresh = u * max_(i>=j) abs(A_ij);
  (2) IF user specifies pivot row k and abs(A_kj) >= thresh THEN
          pivot row = k;
      ELSE IF abs(A_jj) >= thresh THEN
          pivot row = j;
      ELSE
          pivot row = m;

  Note: If you absolutely want to use a given pivot order, then set u=0.0.

  Return value: 0      success;
                i > 0  U(i,i) is exactly zero.