SuperLU: SRC/sp_preorder.c File Reference

SuperLU 6.0.0

Functions
sp_preorder.c File Reference

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

`#include "slu_ddefs.h"`
Include dependency graph for sp_preorder.c:

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

## 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.

## Function Documentation

## ◆ sp_preorder()

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.

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