function umfpack_details
  %UMFPACK_DETAILS details on all the options for using umfpack2 in MATLAB
  %
  % Factor or solve a sparse linear system, returning either the solution x to
  % Ax=b or A'x'=b', the factorization LU=PAQ, or LU=P(R\A)Q.  A must be sparse.
  % For the solve, A must be square and b must be a dense n-by-1 vector.  For LU
  % factorization, A can be rectangular.  In both cases, A and/or b can be real
  % or complex.
  %
  % UMFPACK analyzes the matrix and selects one of three strategies to factorize
  % the matrix.  It first finds a set of k initial pivot entries of zero Markowitz
  % cost.  This forms the first k rows and columns of L and U.  The remaining
  % submatrix S is then analyzed, based on the symmetry of the nonzero pattern of
  % the submatrix and the values on the diagaonal.  The strategies include:
  %
  %       (1) unsymmetric:  use a COLAMD pre-ordering, a column elimination tree
  %           post-ordering, refine the column ordering during factorization,
  %           and make no effort at selecting pivots on the diagonal.
  %       (2) 2-by-2:  like the symmetric strategy (see below), except that local
  %           row permutations are first made to attempt to place large entries
  %           on the diagonal.
  %       (3) symmetric:  use an AMD pre-ordering on the matrix S+S', an
  %           elimination tree post-ordering, do not refine the column ordering
  %           during factorization, and attempt to select pivots on the diagonal.
  %
  % Each of the following uses of umfpack2 (except for "Control = umfpack2") is
  % stand-alone.  That is, no call to umfpack2 is required for any subsequent
  % call.  In each usage, the Info output argument is optional.
  %
  % Example:
  %
  % [x, Info] = umfpack2 (A, '\', b) ;
  % [x, Info] = umfpack2 (A, '\', b, Control) ;
  % [x, Info] = umfpack2 (A, Qinit, '\', b, Control) ;
  % [x, Info] = umfpack2 (A, Qinit, '\', b) ;
  %
  %       Solves Ax=b (similar to x = A\b in MATLAB).
  %
  % [x, Info] = umfpack2 (b, '/', A) ;
  % [x, Info] = umfpack2 (b, '/', A, Control) ;
  % [x, Info] = umfpack2 (b, '/', A, Qinit) ;
  % [x, Info] = umfpack2 (b, '/', A, Qinit, Control) ;
  %
  %       Solves A'x'=b' (similar to x = b/A in MATLAB).
  %
  % [L, U, P, Q, R, Info] = umfpack2 (A) ;
  % [L, U, P, Q, R, Info] = umfpack2 (A, Control) ;
  % [L, U, P, Q, R, Info] = umfpack2 (A, Qinit) ;
  % [L, U, P, Q, R, Info] = umfpack2 (A, Qinit, Control) ;
  %
  %       Returns the LU factorization of A.  P and Q are returned as permutation
  %       matrices.  R is a diagonal sparse matrix of scale factors for the rows
  %       of A, L is lower triangular, and U is upper triangular.  The
  %       factorization is L*U = P*(R\A)*Q.  You can turn off scaling by setting
  %       Control (17) to zero (in which case R = speye (m)), or by using the
  %       following syntaxes (in which case Control (17) is ignored):
  %
  % [L, U, P, Q] = umfpack2 (A) ;
  % [L, U, P, Q] = umfpack2 (A, Control) ;
  % [L, U, P, Q] = umfpack2 (A, Qinit) ;
  % [L, U, P, Q] = umfpack2 (A, Qinit, Control) ;
  %
  %       Same as above, except that no row scaling is performed.  The Info array
  %       is not returned, either.
  %
  % [P1, Q1, Fr, Ch, Info] = umfpack2 (A, 'symbolic') ;
  % [P1, Q1, Fr, Ch, Info] = umfpack2 (A, 'symbolic', Control) ;
  % [P1, Q1, Fr, Ch, Info] = umfpack2 (A, Qinit, 'symbolic') ;
  % [P1, Q1, Fr, Ch, Info] = umfpack2 (A, Qinit, 'symbolic', Control);
  %
  %       Performs only the fill-reducing column pre-ordering (including the
  %       elimination tree post-ordering) and symbolic factorization.  Q1 is the
  %       initial column permutation (either from colamd, amd, or the input
  %       ordering Qinit), possibly followed by a column elimination tree post-
  %       ordering or a symmetric elimination tree post-ordering, depending on
  %       the strategy used.
  %
  %       For the unsymmetric strategy, P1 is the row ordering induced by Q1
  %       (row-merge order). For the 2-by-2 strategy, P1 is the row ordering that
  %       places large entries on the diagonal of P1*A*Q1.  For the symmetric
  %       strategy, P1 = Q1.
  %
  %       Fr is a (nfr+1)-by-4 array containing information about each frontal
  %       matrix, where nfr <= n is the number of frontal matrices.  Fr (:,1) is
  %       the number of pivot columns in each front, and Fr (:,2) is the parent
  %       of each front in the supercolumn elimination tree.  Fr (k,2) is zero if
  %       k is a root.  The first Fr (1,1) columns of P1*A*Q1 are the pivot
  %       columns for the first front, the next Fr (2,1) columns of P1*A*Q1
  %       are the pivot columns for the second front, and so on.
  %
  %       For the unsymmetric strategy, Fr (:,3) is the row index of the first
  %       row in P1*A*Q1 whose leftmost nonzero entry is in a pivot column for
  %       the kth front.  Fr (:,4) is the leftmost descendent of the kth front.
  %       Rows in the range Fr (Fr (k,4),3) to Fr (k+1,3)-1 form the entire set
  %       of candidate pivot rows for the kth front (some of these will typically
  %       have been selected as pivot rows of fronts Fr (k,3) to k-1, before the
  %       factorization reaches the kth front.  If front k is a leaf node, then
  %       Fr (k,4) is k.
  %
  %       Ch is a (nchains+1)-by-3 array containing information about each "chain"
  %       (unifrontal sequence) of frontal matrices, and where nchains <= nfr
  %       is the number of chains.  The ith chain consists of frontal matrices.
  %       Chain (i,1) to Chain (i+1,1)-1, and the largest front in chain i is
  %       Chain (i,2)-by-Chain (i,3).
  %
  %       This use of umfpack2 is not required to factor or solve a linear system
  %       in MATLAB.  It analyzes the matrix A and provides information only.
  %       The MATLAB statement "treeplot (Fr (:,2)')" plots the column elimination
  %       tree.
  %
  % Control = umfpack2 ;
  %
  %       Returns a 20-by-1 vector of default parameter settings for umfpack2.
  %
  % umfpack_report (Control, Info) ;
  %
  %       Prints the current Control settings, and Info
  %
  % det = umfpack2 (A, 'det') ;
  % [det dexp] = umfpack2 (A, 'det') ;
  %
  %       Computes the determinant of A.  The 2nd form returns the determinant
  %       in the form det*10^dexp, where det is in the range +/- 1 to 10,
  %       which helps to avoid overflow/underflow when dexp is out of range of
  %       normal floating-point numbers.
  %
  % If present, Qinit is a user-supplied 1-by-n permutation vector.  It is an
  % initial fill-reducing column pre-ordering for A; if not present, then colamd
  % or amd are used instead.  If present, Control is a user-supplied 20-by-1
  % array.   Control and Info are optional; if Control is not present, defaults
  % are used.  If a Control entry is NaN, then the default is used for that entry.
  %
  %
  % Copyright 1995-2007 by Timothy A. Davis, University of Florida.
  % All Rights Reserved.
  % UMFPACK is available under alternate licenses, contact T. Davis for details.
  %
  % UMFPACK License:
  %
  %   Your use or distribution of UMFPACK or any modified version of
  %   UMFPACK implies that you agree to this License.
  %
  %   This library is free software; you can redistribute it and/or
  %   modify it under the terms of the GNU Lesser General Public
  %   License as published by the Free Software Foundation; either
  %   version 2.1 of the License, or (at your option) any later version.
  %
  %   This library is distributed in the hope that it will be useful,
  %   but WITHOUT ANY WARRANTY; without even the implied warranty of
  %   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  %   Lesser General Public License for more details.
  %
  %   You should have received a copy of the GNU Lesser General Public
  %   License along with this library; if not, write to the Free Software
  %   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
  %   USA
  %
  %   Permission is hereby granted to use or copy this program under the
  %   terms of the GNU LGPL, provided that the Copyright, this License,
  %   and the Availability of the original version is retained on all copies.
  %   User documentation of any code that uses this code or any modified
  %   version of this code must cite the Copyright, this License, the
  %   Availability note, and "Used by permission." Permission to modify
  %   the code and to distribute modified code is granted, provided the
  %   Copyright, this License, and the Availability note are retained,
  %   and a notice that the code was modified is included.
  %
  % Availability: http://www.cise.ufl.edu/research/sparse/umfpack
  %
  % See also umfpack, umfpack2, umfpack_make, umfpack_report,
  %    umfpack_demo, and umfpack_simple.
  
  more on
  help umfpack_details
  more off