%% F van der Heijden - test the speed of matrix-vector multiplication

%% clear all
close all
clear variables

%% set parameters
N = 1000;                           % number of elements in x
M = 5000;                           % number of elements in y

%% initialize arrays
H = randn(M,N);                     % create a random MxN matrix for testing
x = randn(N,1);                     % create a random Nx1 array for testing

%% perform a naive matrix-vector multiplication
tic                                 % start stopwatch
y = zeros(M,1);                     % pre-alllocate y array and fill with zeros
for m=1:M                           % loop through elements of y
    for n=1:N                       % loop through elements of x
        y(m) = y(m)+H(m,n)*x(n);    % perform the calculation
    end
end
toc                                 % read elapsed time from stopwatch