function tensor_test(ndims, len)

% tensor_test -- Test of "tensor_mul" and tensor_sol".
%  tensor_test(ndims, len) exercizes "tensor_mul" and
%   "tensor_sol" with two random arrays, each with
%   ndims, where each dimension has length len.
%   All possible summation directions are tested.
%   The elapsed time and an error-norm are displayed.
%
% Also see: tensor_mul, tensor_sol.
 
% Copyright (C) 1998 Dr. Charles R. Denham, ZYDECO.
%  All Rights Reserved.
%   Disclosure without explicit written consent from the
%    copyright owner does not constitute publication.
 
% Version of 18-Sep-1998 08:41:32.

help(mfilename)

if nargin < 1, ndims = 3; end
if nargin < 2, len = 2; end

if ischar(ndims), ndims = eval(ndims); end
if ischar(len), len = eval(len); end

a = rand(ones(1, ndims)*len) - 0.5;
u = rand(ones(1, ndims)*len) - 0.5;

err = zeros(ndims^2, 1);

tic

k = 0;

for j = 1:ndims
	disp([' ## Remaining: ' int2str(ndims^2 - k)]);
	for i = 1:ndims
		b = tensor_mul(a, u, i, j);
		x = tensor_sol(a, b, i, j);
		k = k+1;
		e = x - u;
		err(k) = norm(e(:));
	end
end

toc

err_norm = norm(err)