clear
warning off 'MATLAB:nearlySingularMatrix'
warning off 'MATLAB:singularMatrix'
index = UFget ;
MatrixList = find (index.posdef) ;
[ignore i] = sort (index.amd_lnz (MatrixList)) ;
MatrixList = MatrixList (i) ;
nmat = length (MatrixList) ;
Tcholmod = -ones (nmat,1) ;
Tbackslash = -ones (nmat,1) ;
Tpcg = -ones (nmat,1) ;
TpcgN = -ones (nmat,1) ;
Rcholmod = -ones (nmat,1) ;
Rbackslash = -ones (nmat,1) ;
Rpcg = -ones (nmat,1) ;
RpcgN = -ones (nmat,1) ;
for k = 1:nmat
    rand ('state', 0) ;
    id = MatrixList (k) ;
    Problem = UFget (id)
    A = Problem.A ;
    clear Problem
    clear b x
    n = size (A,1) ;
    b = rand (n,1);

    % backslash
    try
	tic ;
	x = A\b ;
	t1=toc ;
	r1 = norm (A*x-b,1) / norm (A,1) ;
    catch
	t1 = Inf ;
	r1 = Inf ;
    end
    fprintf ('x=A\\b   time %10.4f  resid: %8.2e\n', t1, r1) ;
    Tbackslash (k) = t1 ;
    Rbackslash (k) = r1 ;

    % cholmod with METIS
    try
	tic ;
	x = cholmod2 (A,b) ;
	t4=toc ;
	r4 = norm (A*x-b,1) / norm (A,1) ;
    catch
	t4 = Inf ;
	r4 = Inf ;
    end
    fprintf ('CHOLMOD time %10.4f  resid: %8.2e\n', t4, r4) ;
    Tcholmod (k) = t4 ;
    Rcholmod (k) = r4 ;

    % preconditioned conjugate-gradient
    try
	M = diag (diag (A)) ; % NOTE: excluded from timing
	tic
	% use defaults for tol and itmax
	[x flag relres iter relres] = pcg (A, b, [ ], [ ], M) ;
	t2=toc ;
	r2 = norm (A*x-b,1) / norm (A,1) ;
    catch
	t2 = Inf ;
	r2 = Inf ;
    end
    fprintf ('PCG     time %10.4f  resid: %8.2e flag: %d iter: %d\n', ...
	t2, r2, flag, length(relres)) ;
    Tpcg (k) = t2 ;
    Rpcg (k) = r2 ;

    % preconditioned conjugate-gradient - many iterations
    try
	tic
	% use defaults for tol, but large itmax
	[x flag relres iter relres] = pcg (A, b, [ ], 200, M) ;
	t3=toc ;
	r3 = norm (A*x-b,1) / norm (A,1) ;
    catch
	t3 = Inf ;
	r3 = Inf ;
    end
    fprintf ('PCG     time %10.4f  resid: %8.2e flag: %d iter: %d\n', ...
	t3, r3, flag, length(relres)) ;
    TpcgN (k) = t3 ;
    RpcgN (k) = r3 ;

    diary off
    diary on
    save Results2 Tcholmod Tbackslash Tpcg Rcholmod Rbackslash Rpcg TpcgN RpcgN MatrixList 
end