1function [p,q,r,s,cc,rr] = cs_dmspy (A,res,seed)
2%CS_DMSPY plot the Dulmage-Mendelsohn decomposition of a matrix.
3%   [p,q,r,s,cc,rr] = cs_dmspy(A) computes [p,q,r,s,cc,rr] = cs_dmperm(A),
4%   does spy(A(p,q)), and then draws boxes around the coarse and fine
5%   decompositions.  A 2nd input argument (cs_dmspy(A,res)) changes the
6%   resolution of the image to res-by-res (default resolution is 256).
7%   If res is zero, spy is used instead of cspy.  If the resolution is low, the
8%   picture of the blocks in the figure can overlap.  They do not actually
9%   overlap in the matrix.  With 3 arguments, cs_dmspy(A,res,seed),
10%   cs_dmperm(A,seed) is used, where seed controls the randomized algorithm
11%   used by cs_dmperm.
12%
13%   Example:
14%       Prob = ssget ('HB/arc130') ; cs_dmspy (Prob.A) ;
15%
16%   See also CS_DMPERM, CS_DMSOL, DMPERM, SPRANK, SPY.
17
18% Copyright 2006-2012, Timothy A. Davis, http://www.suitesparse.com
19
20if (~issparse (A))
21    A = sparse (A) ;
22end
23if (nargin < 2)
24    res = 256 ;
25end
26if (nargin < 3)
27    seed = 0 ;
28end
29
30% Dulmage-Mendelsohn permutation
31[p1,q,r,s,cc,rr] = cs_dmperm (A,seed) ;
32if (nargout > 0)
33    p = p1 ;
34end
35
36nb = length (r)-1 ;
37
38% plot the result
39S = A (p1,q) ;
40if (res == 0)
41    spy (S) ;
42    e = 1 ;
43else
44    e = cspy (S,res) ;
45end
46hold on
47
48title (sprintf ( ...
49    '%d-by-%d, sprank: %d, fine blocks: %d, coarse blocks: %d-by-%d\n', ...
50    size (A), rr(4)-1, nb, length (find (diff (rr))), ...
51    length (find (diff (cc))))) ;
52
53drawboxes (nb, e, r, s) ;
54
55[m n] = size (A) ;
56drawbox (1,m+1,1,n+1,'k',1,e) ;
57
58drawbox (rr(1), rr(2), cc(1), cc (2), 'r', 2, e) ;
59drawbox (rr(1), rr(2), cc(2), cc (3), 'r', 2, e) ;
60drawbox (rr(2), rr(3), cc(3), cc (4), 'k', 2, e) ;
61drawbox (rr(3), rr(4), cc(4), cc (5), 'r', 2, e) ;
62drawbox (rr(4), rr(5), cc(4), cc (5), 'r', 2, e) ;
63
64hold off
65
66