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function [vnz,rnz,parent,c,leftmost,p,q] = cs_sqr (A) %#ok
%CS_SQR symbolic sparse QR factorization.
% [vnz,rnz,parent,c,leftmost,p] = cs_sqr(A): symbolic QR of A(p,:).
% [vnz,rnz,parent,c,leftmost,p,q] = cs_sqr(A) computes the symbolic QR
% factorization of A(p,q). The fill-reducing ordering q is found via
% q = cs_amd(A,3).
%
% vnz is the number of entries in the matrix of Householder vectors, V.
% rnz is the number of entries in R. parent is elimination tree.
% c(i) is the number of entries in R(i,:). leftmost(i) = min(find(A(i,q))).
% p is the row permutation used to ensure R has a symbolically zero-free
% diagonal (it can be larger than m if A is structurally rank deficient).
% q is the fill-reducing ordering, if requested.
%
% Example:
% Prob = ssget ('HB/ibm32') ; A = Prob.A ;
% [vnz, rnz, parent, c, leftmost, p, q] = cs_sqr (A) ;
% cspy (A (p,q)) ;
%
% See also CS_AMD, CS_QR.
% Copyright 2006-2012, Timothy A. Davis, http://www.suitesparse.com
error ('cs_sqr mexFunction not found') ;
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