function baqr
  format compact
  format short
  n=2550;
  A=randn(n);
  xref=randn(n,1);
%  b=double(vpa(sym(A)*sym(xref),32));
  b=A*xref;
%
  tic
  x1=A\b;
  t1=toc
  check1=norm(x1-xref)/norm(xref)
%
  tic
  [L2,U2]=lu(A);
  t2a=toc
  tic
  y=L2\b;
  t2b=toc
  tic
  x2=U2\y;
  t2c=toc
  check2=norm(x2-xref)/norm(xref)
%
  tic
  [L3,U3,P]=lu(A);
  t3a=toc
  tic
  y=L3\(P*b);
  t3b=toc
  tic
  x3=U3\y;
  t3c=toc
  check3=norm(x3-xref)/norm(xref)
%
  tic
  [L4,U4,p]=lu(A,'vector');
  t4a=toc
  tic
  y=L4\b(p);
  t4b=toc
  tic
  x4=U4\y;
  t4c=toc
  check4=norm(x4-xref)/norm(xref)
%
  tic
  opts.LT=true;
  y=linsolve(L4,b(p),opts);
  t5b=toc
  tic
  opts.LT=false;
  opts.UT=true;
  x5=linsolve(U4,y,opts);
  t5c=toc
  check5=norm(x5-xref)/norm(xref)
%
  Aaug=[A b];
  tic
  R=qr(Aaug);
  t6a=toc
  tic
  x6=triu(R(1:n,1:n))\R(:,n+1);
  t6b=toc
  check6=norm(x6-xref)/norm(xref