%DisplayPerf.m
%Jonathan Dorfman
%Math 128B Spring 2005
%Hmwk3 - Solutions (Feb. 5, 2005)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%gPerfCnt is number of iteration samples
%gPerf is structure containing array of eigenvalue and Xn and err info
%cmdStr is 'init', 'reset', or text to be displayed in title
%A is nxn matrix (tolerance when cmdStr='init')
%b is row vector to solve Ax=b'
%x is col vector solution returned by our implementation

function	DisplayPerf(cmdStr, A, b, x);
global	gPerfCnt gPerf
persistent	cr tolStr yLim gFigure

if strcmp(cmdStr, 'init')
	%b = row vector, A=tolerance (overloaded)
	cr		= sprintf('\n');
	n		= length(b);	%for pre-allocating Xn-field
	tol		= A;
	N		= 300;		%initial pre-allocations
	%initialize global variables
	gPerfCnt	= 0;
	gFigure	= 1;
	gPerf		= struct('eigval',zeros(N,1),'err',zeros(N,1),'Xn',zeros(N,n));
	%initialize persistent variables
	yLim		= tol ^ (.1);
	tolStr	= ['{\bfTolerance} = ' num2str(tol) cr];
elseif strcmp(cmdStr, 'reset')
	gPerfCnt	= 0;
else
	%make new figure
	figure(gFigure);
	gFigure	= gFigure + 1;

	%get Matlab's computed solution
	z	= A\b';

	disp(['%%%%%%%%%% ' cmdStr ' %%%%%%%%%%' cr]);

	if (gPerfCnt > 500)
		disp('Failed to converge in 500 iterations');
	end

	iterStr	= 'Number of iterations = ';
	iterStr	= [iterStr num2str(gPerfCnt) cr];
	disp(iterStr);

	str	= 'Error in computed solution (vs. Matlab): ';
	str	= [str num2str(norm(x - z, inf)) cr];
	disp(str);
	str	= ['     [' num2str(x') ']' cr '  vs. [' num2str(z') ']' cr];
	disp(str);

	str	= 'Error in residual: ';
	str	= [str num2str(norm((A*x)' - b, inf)) cr];
	disp(str);

	%display plot of errors
	t	= [1:gPerfCnt];
	zz	= repmat(z,1,gPerfCnt);
	nn	= gPerf.Xn(t,:)' - zz;
	plot(t, max(abs(nn)), 'x', t, gPerf.err(t), 'o');

	%cosmetics (cmdStr is title text)
	legend('|| x^{(k)} - \{Matlab solution\} || _{\infty}', '|| x^{(k)} - x^{(k-1)} || _{\infty}');
	ylim([0, yLim]);
	xlim([1, gPerfCnt]);
	title(['Convergence Statistics for ' cmdStr],'FontSize',12);
	text(0.6, 0.77, tolStr, 'FontSize',10,'Units', 'normalized');
	text(0.6, 0.70, iterStr,'FontSize',10,'Units', 'normalized', 'FontWeight', 'bold');
end
return