% 
% Written by:
% -- 
% John L. Weatherwax                2006-09-03
% 
% email: wax@alum.mit.edu
% 
% Please send comments and especially bug reports to the
% above email address.
% 
%-----

clc; 

n = 1200; 
for jay = 1:4
  if( jay > 1 ) 
    oldtime = time; 
  end
  matrixsize = n
  A = randn(n); 
  x = randn(n,1);
  
  % First multiplication method (matlab's notation):
  % 
  t1 = cputime;
  b = A*x; 
  time1(jay) = cputime - t1;
  
  % Second multiplication method row-oriented matrix-vector with a for loop:
  % 
  t2 = cputime; 
  b=zeros(n,1);
  for ii=1:n,
    b(ii)=0; 
    for jj=1:n
      b(ii) = b(ii)+A(ii,jj)*x(jj);
    end
  end
  time2(jay) = cputime - t2;
  
  
  % Third multiplication method column-oriented matrix-vector with a for loop:
  %
  t3 = cputime; 
  b=zeros(n,1); 
  for jj=1:n,
    for ii=1:n
      b(ii) = b(ii)+A(ii,jj)*x(jj);
    end
  end
  time3(jay) = cputime - t3; 
  
  if( jay > 1 ) 
    ratio = time/oldtime
  end
  n = 2*n;
end

time1
time2
time3