SRC/sp_preorder.c File Reference

Permute and performs functions on columns of orginal matrix. More...

#include "slu_ddefs.h"

Functions
void	sp_preorder (superlu_options_t *options, SuperMatrix *A, int *perm_c, int *etree, SuperMatrix *AC)
int	check_perm (char *what, int n, int *perm)

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Detailed Description

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Function Documentation

int check_perm	(	char *	what,
		int	n,
		int *	perm
	)

void sp_preorder	(	superlu_options_t *	options,
		SuperMatrix *	A,
		int *	perm_c,
		int *	etree,
		SuperMatrix *	AC
	)

 Purpose
 =======

 sp_preorder() permutes the columns of the original matrix. It performs
 the following steps:

    1. Apply column permutation perm_c[] to A's column pointers to form AC;

    2. If options->Fact = DOFACT, then
       (1) Compute column elimination tree etree[] of AC'AC;
       (2) Post order etree[] to get a postordered elimination tree etree[],
           and a postorder permutation post[];
       (3) Apply post[] permutation to columns of AC;
       (4) Overwrite perm_c[] with the product perm_c * post.

 Arguments
 =========

 options (input) superlu_options_t*
         Specifies whether or not the elimination tree will be re-used.
         If options->Fact == DOFACT, this means first time factor A, 
         etree is computed, postered, and output.
         Otherwise, re-factor A, etree is input, unchanged on exit.

 A       (input) SuperMatrix*
         Matrix A in A*X=B, of dimension (A->nrow, A->ncol). The number
         of the linear equations is A->nrow. Currently, the type of A can be:
         Stype = NC or SLU_NCP; Mtype = SLU_GE.
         In the future, more general A may be handled.

 perm_c  (input/output) int*
	   Column permutation vector of size A->ncol, which defines the 
         permutation matrix Pc; perm_c[i] = j means column i of A is 
         in position j in A*Pc.
         If options->Fact == DOFACT, perm_c is both input and output.
         On output, it is changed according to a postorder of etree.
         Otherwise, perm_c is input.

 etree   (input/output) int*
         Elimination tree of Pc'*A'*A*Pc, dimension A->ncol.
         If options->Fact == DOFACT, etree is an output argument,
         otherwise it is an input argument.
         Note: etree is a vector of parent pointers for a forest whose
         vertices are the integers 0 to A->ncol-1; etree[root]==A->ncol.

 AC      (output) SuperMatrix*
         The resulting matrix after applied the column permutation
         perm_c[] to matrix A. The type of AC can be:
         Stype = SLU_NCP; Dtype = A->Dtype; Mtype = SLU_GE.