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function [p, stats] = csymamd (S, knobs, cmember) %#ok
%CSYMAMD constrained symmetric approximate minimum degree permutation
% P = CSYMAMD(S) for a symmetric positive definite matrix S, returns the
% permutation vector p such that S(p,p) tends to have a sparser Cholesky
% factor than S. Sometimes CSYMAMD works well for symmetric indefinite
% matrices too. The matrix S is assumed to be symmetric; only the
% strictly lower triangular part is referenced. S must be square. Note
% that p=amd(S) is faster, but does not allow for a constrained ordering.
% The ordering is followed by an elimination tree post-ordering.
%
% See also AMD, CCOLAMD, COLAMD, SYMAMD.
%
% Example:
% p = csymamd (S)
% p = csymamd (S,knobs,cmember)
%
% knobs is an optional one- to three-element input vector, with a default
% value of [10 1 0] if present or empty ([ ]). Entries not present are set
% to their defaults.
%
% knobs(1): If S is n-by-n, then rows and columns with more than
% max(16,knobs(1)*sqrt(n)) entries are ignored, and ordered last in the
% output permutation (subject to the cmember constraints).
% knobs(2): if nonzero, aggressive absorption is performed.
% knobs(3): if nonzero, statistics and knobs are printed.
%
% cmember is an optional vector of length n. It defines the constraints on
% the ordering. If cmember(j)=s, then row/column j is in constraint set s
% (s must be in the range 1 to n). In the output permutation p,
% rows/columns in set 1 appear first, followed by all rows/columns in set 2,
% and so on. cmember=ones(1,n) if not present or empty. csymamd(S,[],1:n)
% returns 1:n.
%
% p = csymamd(S) is about the same as p = symamd(S). knobs and its default
% values differ.
%
% Authors: S. Larimore, T. Davis, and S. Rajamanickam, in
% collaboration with J. Gilbert and E. Ng. Supported by the National
% Science Foundation (DMS-9504974, DMS-9803599, CCR-0203270), and a grant
% from Sandia National Lab. See http://www.suitesparse.com
% for ccolamd, csymamd, amd, colamd, symamd, and other related orderings.
%
% See also AMD, CCOLAMD, COLAMD, SYMAMD, SYMRCM.
% Copyright 1998-2007, Timothy A. Davis, Stefan Larimore, and Siva Rajamanickam
% Developed in collaboration with J. Gilbert and E. Ng.
error ('csymamd: mexFunction not found') ;
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