62 lines
1.7 KiB
Matlab
62 lines
1.7 KiB
Matlab
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);
|