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+## Copyright (C) 2009 E. Jason Riedy
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or (at
+## your option) any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+########################################
+## Permutation matrices
+
+## row permutation
+%!test
+%! n = 5;
+%! A = rand (n);
+%! perm = randperm (n);
+%! Prow = eye (n) (perm, :);
+%! assert (A(perm, :), Prow * A);
+%! invperm(perm) = 1:n;
+%! assert (Prow \ A, A(invperm, :));
+%! assert (Prow' * A, A(invperm, :));
+
+## column permutation
+%!test
+%! n = 7;
+%! A = rand (n);
+%! perm = randperm (n);
+%! Pcol = eye (n) (:, perm);
+%! assert (A(:, perm), A * Pcol);
+%! invperm(perm) = 1:n;
+%! assert (A / Pcol, A(:, invperm));
+%! assert (A * Pcol.', A(:, invperm));
+
+## fall back to a matrix in addition
+%!test
+%! n = 4;
+%! P1 = eye (n) (:, randperm (n));
+%! A = zeros (n) + P1;
+%! assert (sum (A), ones (1, n));
+%! assert (sum (A, 2), ones (n, 1));
+
+## preserve dense matrix structure
+%!test
+%! n = 7;
+%! Pc = eye (n) (:, randperm (n));
+%! Pr = eye (n) (randperm (n), :);
+%! assert (typeinfo (rand (n) * Pc), "matrix");
+%! assert (typeinfo (Pr * rand (n)), "matrix");
+
+## permuting a matrix with exceptional values does not introduce new ones.
+%!test
+%! n = 5;
+%! pc = randperm (n);
+%! Pc = eye (n) (:, pc);
+%! pr = randperm (n);
+%! Pr = eye (n) (pr, :);
+%! A = rand (n);
+%! A(n, n-2) = NaN;
+%! A(3, 1) = Inf;
+%! assert (Pr * A * Pc, A(pr, pc));
+
+########################################
+## Diagonal matrices
+
+## square row scaling
+%!test
+%! m = 7;
+%! n = 11;
+%! A = rand (m, n);
+%! scalefact = rand (m, 1);
+%! Dr = diag (scalefact);
+%! assert (Dr * A, repmat (scalefact, 1, n) .* A);
+%! assert (Dr \ A, A ./ repmat (scalefact, 1, n));
+%! scalefact(m-1) = Inf;
+%! Dr(m-1, m-1) = 0;
+%! assert (Dr \ A, A ./ repmat (scalefact, 1, n));
+
+## square column scaling
+%!test
+%! m = 13;
+%! n = 11;
+%! A = rand (m, n);
+%! scalefact = rand (1, n);
+%! Dc = diag (scalefact);
+%! assert (A * Dc, repmat (scalefact, m, 1) .* A);
+%! assert (A / Dc, A ./ repmat (scalefact, m, 1));
+%! scalefact(n-1) = Inf;
+%! Dc(n-1, n-1) = 0;
+%! assert (A / Dc, A ./ repmat (scalefact, m, 1));
+
+## arithmetic
+%!test
+%! m = 9;
+%! n = 7;
+%! mn = min (m, n);
+%! d1 = rand (mn, 1) + I () * rand (mn, 1);
+%! D1 = diag (d1, m, n);
+%! d2 = rand (mn, 1);
+%! D2 = diag (d2, m, n);
+%! D1D2 = D1 + D2;
+%! assert (typeinfo (D1D2), "complex diagonal matrix");
+%! assert (diag (D1D2), d1 + d2);
+%! D1D2 = D2.' * D1;
+%! assert (typeinfo (D1D2), "complex diagonal matrix");
+%! assert (diag (D1D2), d1 .* d2);
+
+## slicing
+%!test
+%! m = 13;
+%! n = 6;
+%! mn = min (m, n);
+%! d = rand (mn, 1);
+%! D = diag (d, m, n);
+%! Dslice = D (1:(m-3), 1:(n-2));
+%! assert (typeinfo (Dslice), "diagonal matrix");
+
+## preserve dense matrix structure
+%!assert (typeinfo (rand (8) * (3 * eye (8))), "matrix");
+%!assert (typeinfo ((3 * eye (8)) * rand (8)), "matrix");
+
+## scaling a matrix with exceptional values does not introduce new ones.
+%!test
+%! n = 6;
+%! dr = rand (n, 1);
+%! Dr = diag (dr);
+%! dc = rand (1, n);
+%! Dc = diag (dc);
+%! A = rand (n);
+%! A(n, n-2) = NaN;
+%! A(4, 1) = Inf;
+%! assert (Dr * A * Dc, A .* kron (dr, dc), eps);
+