1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
|
function x = lusolve(A,b,Pcol)
% LUSOLVE : Solve linear systems by supernodal LU factorization.
%
% x = lusolve(A, b) returns the solution to the linear system A*x = b,
% using a supernodal LU factorization that is faster than Matlab's
% builtin LU. This m-file just calls a mex routine to do the work.
%
% By default, A is preordered by column minimum degree before factorization.
% Optionally, the user can supply a desired column ordering:
%
% x = lusolve(A, b, pcol) uses pcol as a column permutation.
% It still returns x = A\b, but it factors A(:,pcol) (if pcol is a
% permutation vector) or A*Pcol (if Pcol is a permutation matrix).
%
% x = lusolve(A, b, 0) suppresses the default minimum degree ordering;
% that is, it forces the identity permutation on columns.
%
% See also SUPERLU.
%
% John Gilbert, 6 April 1995
% Copyright (c) 1995 by Xerox Corporation. All rights reserved.
% HELP COPYRIGHT for complete copyright and licensing notice.
[m,n] = size(A);
if m ~= n
error('matrix must be square');
end;
[mb,nb] = size(b);
if mb ~= n
error('right-hand side must have same row dimension as matrix');
end;
if n == 0
x = [];
return;
end;
% As necessary, compute the column permutation, and
% convert it from a permutation vector to a permutation matrix
% to fit the internal data structures of mexlusolve.
if nargin < 3
Pcol = colamd(A);
end;
if isempty(Pcol) | Pcol == 0
Pcol = speye(n);
end;
if min(size(Pcol)) == 1
Pcol = sparse(1:n,Pcol,1,n,n);
end;
% Make sure the matrices are sparse and the vector is full.
if ~issparse(A)
A = sparse(A);
end;
if issparse(b)
b = full(b);
end;
if ~issparse(Pcol)
Pcol = sparse(Pcol);
end;
x = mexlusolve(A,b,Pcol);
|
