% Introduction to MatLab - LOOPS

%clear memory and screen
clear all; clc;

%%
%---------------------------------------
%LOOPS VS MATRICIAL CODING
%---------------------------------------
clear all;              %clear memory
a=-10; b=10; c=0.001;   %some constants
fprintf('LOOPS VS MATRICIAL CODING');
fprintf('\n');

start_time=clock; start_cpu=cputime; %initialize timing variables
for i=1:(b-a)/c+1
    x(i,1) = a+(i-1)*c;
end
% End program and print out the results
end_time=clock; end_cpu=cputime;
fprintf('Program executed in %10.5f seconds',etime(end_time,start_time));
fprintf('\n');
fprintf('Using %24.5f CPU time', end_cpu-start_cpu);
fprintf('\n');

start_time=clock; start_cpu=cputime; %initialize timing variables
y=a:c:b;
% End program and print out the results
end_time=clock; end_cpu=cputime;
fprintf('Program executed in %10.5f seconds',etime(end_time,start_time));
fprintf('\n');
fprintf('Using %24.5f CPU time', end_cpu-start_cpu);
fprintf('\n');

%%
%----------------------------------------
%LOOPS - TREATEMENT OF THE INVARIANT CODE
%----------------------------------------
clear all;              %clear memory
I=500000;                %number of iterations in the loops
mu = 0.1;               %some constant
fprintf('LOOPS - TREATEMENT OF THE INVARIANT CODE');
fprintf('\n');

start_time=clock; start_cpu=cputime; %initialize timing variables
x = zeros(I,1);
for i=1:I
    x(i,1) = i*exp(mu);
end
% End program and print out the results
end_time=clock; end_cpu=cputime;
fprintf('Program executed in %10.5f seconds',etime(end_time,start_time));
fprintf('\n');
fprintf('Using %24.5f CPU time', end_cpu-start_cpu);
fprintf('\n');

start_time=clock; start_cpu=cputime; %initialize timing variables
y = zeros(I,1);
for ii=1:I
    y(ii,1) = ii;
end
y = y.*exp(mu);
% End program and print out the results
end_time=clock; end_cpu=cputime;
fprintf('Program executed in %10.5f seconds',etime(end_time,start_time));
fprintf('\n');
fprintf('Using %24.5f CPU time', end_cpu-start_cpu);
fprintf('\n');

%%
%--------------
%EMBEDDED LOOPS
%--------------
clear all;              %clear memory
I=100000; J=10;         %numbers of oterations in the loops
fprintf('EMBEDDED LOOPS');
fprintf('\n');

start_time=clock; start_cpu=cputime; %initialize timing variables
for i=1:I
    for j=1:J
        x=i*j;
    end
end
% End program and print out the results
end_time=clock; end_cpu=cputime;
fprintf('Program executed in %10.5f seconds',etime(end_time,start_time));
fprintf('\n');
fprintf('Using %24.5f CPU time', end_cpu-start_cpu);
fprintf('\n');

start_time=clock; start_cpu=cputime; %initialize timing variables
for jj=1:J
    for ii=1:I
        y=ii*jj;
    end
end
% End program and print out the results
end_time=clock; end_cpu=cputime;
fprintf('Program executed in %10.5f seconds',etime(end_time,start_time));
fprintf('\n');
fprintf('Using %24.5f CPU time', end_cpu-start_cpu);
fprintf('\n');

%%
%----------------------
%LOOPS - PRE-ALLOCATION
%----------------------
clear all;              %clear memory
I=20000; J=10;          %numbers of oterations in the loops
fprintf('LOOPS - PRE-ALLOCATION');
fprintf('\n');

start_time=clock; start_cpu=cputime; %initialize timing variables
for j=1:J
    for i=1:I
        x(i,j)=i*j;
    end
end
% End program and print out the results
end_time=clock; end_cpu=cputime;
fprintf('Program executed in %10.5f seconds',etime(end_time,start_time));
fprintf('\n');
fprintf('Using %24.5f CPU time', end_cpu-start_cpu);
fprintf('\n');

start_time=clock; start_cpu=cputime; %initialize timing variables
y = zeros(I,J);
for jj=1:J
    for ii=1:I
        y(ii,jj)=ii*jj;
    end
end
% End program and print out the results
end_time=clock; end_cpu=cputime;
fprintf('Program executed in %10.5f seconds',etime(end_time,start_time));
fprintf('\n');
fprintf('Using %24.5f CPU time', end_cpu-start_cpu);
fprintf('\n');

%%
%-------------------
%MATRICES: DIMENSION
%-------------------
clear all;              %clear memory
I=1000; J=10;           %matrices' dimension
fprintf('MATRICES: DIMENSION');
fprintf('\n');


start_time=clock; start_cpu=cputime; %initialize timing variables
x = zeros(J,I);
for j=1:J
    for i=1:I
        x(i,j)=i*j;
    end
end
% End program and print out the results
end_time=clock; end_cpu=cputime;
fprintf('Program executed in %10.5f seconds',etime(end_time,start_time));
fprintf('\n');
fprintf('Using %24.5f CPU time', end_cpu-start_cpu);
fprintf('\n');

start_time=clock; start_cpu=cputime; %initialize timing variables
y = zeros(I,J);
for jj=1:J
    for ii=1:I
        y(ii,jj)=ii*jj;
    end
end
% End program and print out the results
end_time=clock; end_cpu=cputime;
fprintf('Program executed in %10.5f seconds',etime(end_time,start_time));
fprintf('\n');
fprintf('Using %24.5f CPU time', end_cpu-start_cpu);
fprintf('\n');