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+/* ========================================================================== */
+/* === BTF package ========================================================== */
+/* ========================================================================== */
+
+/* BTF_MAXTRANS: find a column permutation Q to give A*Q a zero-free diagonal
+ * BTF_STRONGCOMP: find a symmetric permutation P to put P*A*P' into block
+ * upper triangular form.
+ * BTF_ORDER: do both of the above (btf_maxtrans then btf_strongcomp).
+ *
+ * By Tim Davis. Copyright (c) 2004-2007, University of Florida.
+ * with support from Sandia National Laboratories. All Rights Reserved.
+ */
+
+
+/* ========================================================================== */
+/* === BTF_MAXTRANS ========================================================= */
+/* ========================================================================== */
+
+/* BTF_MAXTRANS: finds a permutation of the columns of a matrix so that it has a
+ * zero-free diagonal. The input is an m-by-n sparse matrix in compressed
+ * column form. The array Ap of size n+1 gives the starting and ending
+ * positions of the columns in the array Ai. Ap[0] must be zero. The array Ai
+ * contains the row indices of the nonzeros of the matrix A, and is of size
+ * Ap[n]. The row indices of column j are located in Ai[Ap[j] ... Ap[j+1]-1].
+ * Row indices must be in the range 0 to m-1. Duplicate entries may be present
+ * in any given column. The input matrix is not checked for validity (row
+ * indices out of the range 0 to m-1 will lead to an undeterminate result -
+ * possibly a core dump, for example). Row indices in any given column need
+ * not be in sorted order. However, if they are sorted and the matrix already
+ * has a zero-free diagonal, then the identity permutation is returned.
+ *
+ * The output of btf_maxtrans is an array Match of size n. If row i is matched
+ * with column j, then A(i,j) is nonzero, and then Match[i] = j. If the matrix
+ * is structurally nonsingular, all entries in the Match array are unique, and
+ * Match can be viewed as a column permutation if A is square. That is, column
+ * k of the original matrix becomes column Match[k] of the permuted matrix. In
+ * MATLAB, this can be expressed as (for non-structurally singular matrices):
+ *
+ * Match = maxtrans (A) ;
+ * B = A (:, Match) ;
+ *
+ * except of course here the A matrix and Match vector are all 0-based (rows
+ * and columns in the range 0 to n-1), not 1-based (rows/cols in range 1 to n).
+ * The MATLAB dmperm routine returns a row permutation. See the maxtrans
+ * mexFunction for more details.
+ *
+ * If row i is not matched to any column, then Match[i] is == -1. The
+ * btf_maxtrans routine returns the number of nonzeros on diagonal of the
+ * permuted matrix.
+ *
+ * In the MATLAB mexFunction interface to btf_maxtrans, 1 is added to the Match
+ * array to obtain a 1-based permutation. Thus, in MATLAB where A is m-by-n:
+ *
+ * q = maxtrans (A) ; % has entries in the range 0:n
+ * q % a column permutation (only if sprank(A)==n)
+ * B = A (:, q) ; % permuted matrix (only if sprank(A)==n)
+ * sum (q > 0) ; % same as "sprank (A)"
+ *
+ * This behaviour differs from p = dmperm (A) in MATLAB, which returns the
+ * matching as p(j)=i if row i and column j are matched, and p(j)=0 if column j
+ * is unmatched.
+ *
+ * p = dmperm (A) ; % has entries in the range 0:m
+ * p % a row permutation (only if sprank(A)==m)
+ * B = A (p, :) ; % permuted matrix (only if sprank(A)==m)
+ * sum (p > 0) ; % definition of sprank (A)
+ *
+ * This algorithm is based on the paper "On Algorithms for obtaining a maximum
+ * transversal" by Iain Duff, ACM Trans. Mathematical Software, vol 7, no. 1,
+ * pp. 315-330, and "Algorithm 575: Permutations for a zero-free diagonal",
+ * same issue, pp. 387-390. Algorithm 575 is MC21A in the Harwell Subroutine
+ * Library. This code is not merely a translation of the Fortran code into C.
+ * It is a completely new implementation of the basic underlying method (depth
+ * first search over a subgraph with nodes corresponding to columns matched so
+ * far, and cheap matching). This code was written with minimal observation of
+ * the MC21A/B code itself. See comments below for a comparison between the
+ * maxtrans and MC21A/B codes.
+ *
+ * This routine operates on a column-form matrix and produces a column
+ * permutation. MC21A uses a row-form matrix and produces a row permutation.
+ * The difference is merely one of convention in the comments and interpretation
+ * of the inputs and outputs. If you want a row permutation, simply pass a
+ * compressed-row sparse matrix to this routine and you will get a row
+ * permutation (just like MC21A). Similarly, you can pass a column-oriented
+ * matrix to MC21A and it will happily return a column permutation.
+ */
+
+#ifndef _BTF_H
+#define _BTF_H
+
+/* make it easy for C++ programs to include BTF */
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "SuiteSparse_config.h"
+
+int btf_maxtrans /* returns # of columns matched */
+(
+ /* --- input, not modified: --- */
+ int nrow, /* A is nrow-by-ncol in compressed column form */
+ int ncol,
+ int Ap [ ], /* size ncol+1 */
+ int Ai [ ], /* size nz = Ap [ncol] */
+ double maxwork, /* maximum amount of work to do is maxwork*nnz(A); no limit
+ * if <= 0 */
+
+ /* --- output, not defined on input --- */
+ double *work, /* work = -1 if maxwork > 0 and the total work performed
+ * reached the maximum of maxwork*nnz(A).
+ * Otherwise, work = the total work performed. */
+
+ int Match [ ], /* size nrow. Match [i] = j if column j matched to row i
+ * (see above for the singular-matrix case) */
+
+ /* --- workspace, not defined on input or output --- */
+ int Work [ ] /* size 5*ncol */
+) ;
+
+/* long integer version (all "int" parameters become "SuiteSparse_long") */
+SuiteSparse_long btf_l_maxtrans (SuiteSparse_long, SuiteSparse_long,
+ SuiteSparse_long *, SuiteSparse_long *, double, double *,
+ SuiteSparse_long *, SuiteSparse_long *) ;
+
+
+/* ========================================================================== */
+/* === BTF_STRONGCOMP ======================================================= */
+/* ========================================================================== */
+
+/* BTF_STRONGCOMP finds the strongly connected components of a graph, returning
+ * a symmetric permutation. The matrix A must be square, and is provided on
+ * input in compressed-column form (see BTF_MAXTRANS, above). The diagonal of
+ * the input matrix A (or A*Q if Q is provided on input) is ignored.
+ *
+ * If Q is not NULL on input, then the strongly connected components of A*Q are
+ * found. Q may be flagged on input, where Q[k] < 0 denotes a flagged column k.
+ * The permutation is j = BTF_UNFLIP (Q [k]). On output, Q is modified (the
+ * flags are preserved) so that P*A*Q is in block upper triangular form.
+ *
+ * If Q is NULL, then the permutation P is returned so that P*A*P' is in upper
+ * block triangular form.
+ *
+ * The vector R gives the block boundaries, where block b is in rows/columns
+ * R[b] to R[b+1]-1 of the permuted matrix, and where b ranges from 1 to the
+ * number of strongly connected components found.
+ */
+
+int btf_strongcomp /* return # of strongly connected components */
+(
+ /* input, not modified: */
+ int n, /* A is n-by-n in compressed column form */
+ int Ap [ ], /* size n+1 */
+ int Ai [ ], /* size nz = Ap [n] */
+
+ /* optional input, modified (if present) on output: */
+ int Q [ ], /* size n, input column permutation */
+
+ /* output, not defined on input */
+ int P [ ], /* size n. P [k] = j if row and column j are kth row/col
+ * in permuted matrix. */
+
+ int R [ ], /* size n+1. block b is in rows/cols R[b] ... R[b+1]-1 */
+
+ /* workspace, not defined on input or output */
+ int Work [ ] /* size 4n */
+) ;
+
+SuiteSparse_long btf_l_strongcomp (SuiteSparse_long, SuiteSparse_long *,
+ SuiteSparse_long *, SuiteSparse_long *, SuiteSparse_long *,
+ SuiteSparse_long *, SuiteSparse_long *) ;
+
+
+/* ========================================================================== */
+/* === BTF_ORDER ============================================================ */
+/* ========================================================================== */
+
+/* BTF_ORDER permutes a square matrix into upper block triangular form. It
+ * does this by first finding a maximum matching (or perhaps a limited matching
+ * if the work is limited), via the btf_maxtrans function. If a complete
+ * matching is not found, BTF_ORDER completes the permutation, but flags the
+ * columns of P*A*Q to denote which columns are not matched. If the matrix is
+ * structurally rank deficient, some of the entries on the diagonal of the
+ * permuted matrix will be zero. BTF_ORDER then calls btf_strongcomp to find
+ * the strongly-connected components.
+ *
+ * On output, P and Q are the row and column permutations, where i = P[k] if
+ * row i of A is the kth row of P*A*Q, and j = BTF_UNFLIP(Q[k]) if column j of
+ * A is the kth column of P*A*Q. If Q[k] < 0, then the (k,k)th entry in P*A*Q
+ * is structurally zero.
+ *
+ * The vector R gives the block boundaries, where block b is in rows/columns
+ * R[b] to R[b+1]-1 of the permuted matrix, and where b ranges from 1 to the
+ * number of strongly connected components found.
+ */
+
+int btf_order /* returns number of blocks found */
+(
+ /* --- input, not modified: --- */
+ int n, /* A is n-by-n in compressed column form */
+ int Ap [ ], /* size n+1 */
+ int Ai [ ], /* size nz = Ap [n] */
+ double maxwork, /* do at most maxwork*nnz(A) work in the maximum
+ * transversal; no limit if <= 0 */
+
+ /* --- output, not defined on input --- */
+ double *work, /* return value from btf_maxtrans */
+ int P [ ], /* size n, row permutation */
+ int Q [ ], /* size n, column permutation */
+ int R [ ], /* size n+1. block b is in rows/cols R[b] ... R[b+1]-1 */
+ int *nmatch, /* # nonzeros on diagonal of P*A*Q */
+
+ /* --- workspace, not defined on input or output --- */
+ int Work [ ] /* size 5n */
+) ;
+
+SuiteSparse_long btf_l_order (SuiteSparse_long, SuiteSparse_long *,
+ SuiteSparse_long *, double , double *, SuiteSparse_long *,
+ SuiteSparse_long *, SuiteSparse_long *, SuiteSparse_long *,
+ SuiteSparse_long *) ;
+
+
+/* ========================================================================== */
+/* === BTF marking of singular columns ====================================== */
+/* ========================================================================== */
+
+/* BTF_FLIP is a "negation about -1", and is used to mark an integer j
+ * that is normally non-negative. BTF_FLIP (-1) is -1. BTF_FLIP of
+ * a number > -1 is negative, and BTF_FLIP of a number < -1 is positive.
+ * BTF_FLIP (BTF_FLIP (j)) = j for all integers j. UNFLIP (j) acts
+ * like an "absolute value" operation, and is always >= -1. You can test
+ * whether or not an integer j is "flipped" with the BTF_ISFLIPPED (j)
+ * macro.
+ */
+
+#define BTF_FLIP(j) (-(j)-2)
+#define BTF_ISFLIPPED(j) ((j) < -1)
+#define BTF_UNFLIP(j) ((BTF_ISFLIPPED (j)) ? BTF_FLIP (j) : (j))
+
+/* ========================================================================== */
+/* === BTF version ========================================================== */
+/* ========================================================================== */
+
+/* All versions of BTF include these definitions.
+ * As an example, to test if the version you are using is 1.2 or later:
+ *
+ * if (BTF_VERSION >= BTF_VERSION_CODE (1,2)) ...
+ *
+ * This also works during compile-time:
+ *
+ * #if (BTF >= BTF_VERSION_CODE (1,2))
+ * printf ("This is version 1.2 or later\n") ;
+ * #else
+ * printf ("This is an early version\n") ;
+ * #endif
+ */
+
+#define BTF_DATE "Jun 1, 2012"
+#define BTF_VERSION_CODE(main,sub) ((main) * 1000 + (sub))
+#define BTF_MAIN_VERSION 1
+#define BTF_SUB_VERSION 2
+#define BTF_SUBSUB_VERSION 0
+#define BTF_VERSION BTF_VERSION_CODE(BTF_MAIN_VERSION,BTF_SUB_VERSION)
+
+#ifdef __cplusplus
+}
+#endif
+#endif