function leastime
% *** m=2*n ***
  A=randn(2000,1000);
  b=randn(2000,1);
%
% *** Least squares via projected equations ***
% *** complexity     2*m*n^2-2*n^3/3  => 10*n^3/3 FLOPs
  tic
  x1=A\b;                    
  t1=toc
%  
% *** minor improvement with linsolve ***  
  opts.RECT=true;
  tic
  x2=linsolve(A,b,opts);
  t2=toc
  opts.RECT=false;
% 
% *** Least squares via normal equations ***
% *** (classic complexity m*n^2+n^3/3  =>  7*n^3/3 FLOPs )
% *** complexity here 2*m*n^2+n^3/3    => 13*n^3/3 FLOPs 
%
  tic
  x3=(A'*A)\(A'*b);  
  t3=toc                     
%
% *** minor improvement with linsolve ***  
  opts.SYM=true;
  opts.POSDEF=true;
  tic
  x4=linsolve(A'*A,A'*b,opts);
  t4=toc
  opts.SYM=false;
  opts.POSDEF=false;
%  
  kolla2=norm(x2-x1)/norm(x1)
  kolla3=norm(x3-x1)/norm(x1)  
  kolla4=norm(x4-x1)/norm(x1)