How can I randomly excuted for loops inside MAIN FOR LOOP instead of run them in ordered ?

I want to select one of these for loops randmly to excute them NOT in ordered from loop 1 to loop 2 to Loop 3. for example in the first iteration of the main loop, Loop 3 is executed first and in the second iteration again selecting is randomly.

Thanks in advance

for q=1:100                    % MAIN LOOP
    
    for q1=1:10                % Loop 1
        do some calculation
    end
    for q2=1:10                % Loop 2
        do some calculation
    end
    for q3=1:10                % Loop 3
        do some calculation
    end
    
end

Answer 1

[Aritra]

Hi @omar th,

As per my understanding you are trying to execute the nested loops in random order inside the Main for Loop.

The order of execution of a for loop is linear. This behavior cannot be altered. However, you can use a randperm(n,k) function to generate a random number and the use the switch, case, otherwise expression in matlab to randomly execute a certain for loop.

To do so you can use a similar code snippet:

for q=1:5                    % MAIN LOOP 
    t = randperm(3,1);     
    switch t 
        case 1 
            for q1=1:10                % Loop 1 
                disp(1); 
            end 
        case 2 
            for q2=1:10                % Loop 2 
                disp(2); 
            end 
        case 3 
            for q3=1:10                % Loop 3 
                disp(3); 
            end 
    end 
end 

For detail, please see this MathWorks documentation below for more information on randperm:

https://in.mathworks.com/help/matlab/ref/randperm.html#d124e1236178

For detail, please see this MathWorks documentation below for more information on switch, case, otherwise:

https://in.mathworks.com/help/matlab/ref/switch.html

[omar th]

Thank you so much for your clear answer

[omar th]

@Aritra , When I run my code let's assume loop 2 is executed but I have a function in loop 3 and 1 are not executed. As illustrated in the code below, when I obtained the summuation of these functions, two of them is not executed thats why I got an error in

Sum_Total_Functions

. Thanks in advance for any help.

for q=1:5                    % MAIN LOOP 
    t = randperm(3,1);     
    switch t 
        case 1 
            for q1=1:10                % Loop 1 
                disp(1); 
                Function_1(q1) = do some calculation
            end 
        case 2 
            for q2=1:10                % Loop 2 
                disp(2);
                Function_2(q2) = do some calculation
            end 
        case 3 
            for q3=1:10                % Loop 3 
                disp(3); 
                Function_3(q3) = do some calculation
            end 
    end 
end 
Sum_Total_Functions = Function_1+Function_2+Function_3;

[Aritra]

Hi @omar th

You can set initial default values like '0' for each variable (Function_1, Function_2, and Function_3). It will help you get rid of the error.

If a certain for loop fails to execute, the sum_Total_Functions variable will use the default values to generate the final result.

[omar th]

Hi @Aritra How can I let all loops be executed but in random way not sequentially, for example loop three executed first then loop one after that loop two based on your previous answer instead of choosing only one loop. I would appreciate any help for that.

for q=1:5                    % MAIN LOOP 
    t = randperm(3,1);     
    switch t 
        case 1 
            for q1=1:10                % Loop 1 
                disp(1); 
            end 
        case 2 
            for q2=1:10                % Loop 2 
                disp(2); 
            end 
        case 3 
            for q3=1:10                % Loop 3 
                disp(3); 
            end 
    end 
end 

[Aritra]

Hi @omar th

You can use the perms function to generate all permutations of a given sequence. Select a randomly permutated sequence using the randperm(n,k) function. Finally, use the swtich case block to execute all the nested for loops in a random order.

To do so you can use a similar code snippet:

A = [1 2 3];
PermutationA = perms(A);
t = randperm(6,1);
for q=1:3                    % MAIN LOOP 
    j = PermutationA(t,q);
    switch j 
        case 1 
            for q1=1:3             % Loop 1 
                disp(1); 
            end 
        case 2 
            for q2=1:3              % Loop 2 
                disp(2); 
            end 
        case 3 
            for q3=1:3              % Loop 3 
                disp(3); 
            end 
    end 
end   

[Walter Roberson]

randperm(6,1) is equivalent to randi(6,1,1)

If you want to choose a random order you can

t = randperm(3);
for q = 1 : length(t)
    j = t(q);
    switch j
        stuff
    end
end

[omar th]

@Walter Roberson thank you for your response

Answer 2

[Jiri Hajek]

Hi, use randperm function to generate the random ordering.

growingOrder = 1:10;
randomOrder = growingOrder(randperm(length(growingOrder)));

For the random calling of loops, use switch-case command:

currentLoopIndex = randomOrder(q);
switch currentLoopIndex
    case growingOrder(1)
        % loop 1
    case growingOrder(2)
        % loop 2
    case growingOrder(3)
        % loop 3
end

[omar th]

Thank you so much for your response

Answer 3

[Steven Lord]

Another possible solution to the problem, if you want to run a series of functions in a loop in a random order, is to use a cell array of function handles.

The line functionsToExecute{whichFunction}() extracts one of the three function handles from the cell array functionsToExecute then calls that function handle with no input arguments. The empty parentheses are necessary to call the function rather than simply displaying the function handle.

functionsToExecute = {@function1, @function2, @function3WithLoop};
for k = 1:5
    orderOfFunctions = randperm(3);
    for whichFunction = orderOfFunctions
        fprintf("At iteration k = %d, running function %d\n", k, whichFunction)
        functionsToExecute{whichFunction}()
    end
    fprintf("Outer loop iteration k = %d complete!\n \n", k)
end

At iteration k = 1, running function 1

Inside function 1

At iteration k = 1, running function 2

Function 2, executing!

At iteration k = 1, running function 3

function3WithLoop executing inner loop iteration k = 1
function3WithLoop executing inner loop iteration k = 2
function3WithLoop executing inner loop iteration k = 3

Outer loop iteration k = 1 complete!
 

At iteration k = 2, running function 2

Function 2, executing!

At iteration k = 2, running function 1

Inside function 1

At iteration k = 2, running function 3

function3WithLoop executing inner loop iteration k = 1
function3WithLoop executing inner loop iteration k = 2
function3WithLoop executing inner loop iteration k = 3

Outer loop iteration k = 2 complete!
 

At iteration k = 3, running function 2

Function 2, executing!

At iteration k = 3, running function 1

Inside function 1

At iteration k = 3, running function 3

function3WithLoop executing inner loop iteration k = 1
function3WithLoop executing inner loop iteration k = 2
function3WithLoop executing inner loop iteration k = 3

Outer loop iteration k = 3 complete!
 

At iteration k = 4, running function 2

Function 2, executing!

At iteration k = 4, running function 3

function3WithLoop executing inner loop iteration k = 1
function3WithLoop executing inner loop iteration k = 2
function3WithLoop executing inner loop iteration k = 3

At iteration k = 4, running function 1

Inside function 1

Outer loop iteration k = 4 complete!
 

At iteration k = 5, running function 2

Function 2, executing!

At iteration k = 5, running function 3

function3WithLoop executing inner loop iteration k = 1
function3WithLoop executing inner loop iteration k = 2
function3WithLoop executing inner loop iteration k = 3

At iteration k = 5, running function 1

Inside function 1

Outer loop iteration k = 5 complete!
 

function function1
    disp("Inside function 1")
end
function function2
    disp("Function 2, executing!")
end
function function3WithLoop
    for k = 1:3
        fprintf("function3WithLoop executing inner loop iteration k = %d\n", k)
    end
end

Answer 4

[Sarvesh Kale]

Hi omar th,

I have borrowed a part of answer from Jiri Hajek, you can acheive the random execution of loop using following lines of code

% pre define a random generated array and call it select 
select = randi([1,3],1,100);   % this will create a random vector whose entries will be 1, 2, or 3
for q=1:100                    % MAIN LOOP    
 switch select(q)
    case 1
        for q1=1:10                % Loop 1
            %do some calculation
        end        
    case 2
        for q2=1:10                % Loop 2
            %do some calculation
        end
    case 3
        for q3=1:10                % Loop 3
            %do some calculation
        end 
 end
end

[omar th]

Thank you for your reply

[omar th]

@Sarvesh Kale , When I run my code let's assume loop 2 is executed but I have a function in loop 3 and 1 are not executed. As illustrated in the code below, when I obtained the summuation of these functions, two of them is not executed thats why I got an error in " Sum_Total_Functions ". I appreciate any help

for q=1:5                    % MAIN LOOP 
    t = randperm(3,1);     
    switch t 
        case 1 
            for q1=1:10                % Loop 1 
                disp(1); 
                Function_1(q1) = do some calculation
            end 
        case 2 
            for q2=1:10                % Loop 2 
                disp(2);
                Function_2(q2) = do some calculation
            end 
        case 3 
            for q3=1:10                % Loop 3 
                disp(3); 
                Function_3(q3) = do some calculation
            end 
    end 
end 
Sum_Total_Functions = Function_1+Function_2+Function_3;

[Walter Roberson]

Do not randperm each iteration separately. Your code t = randperm(3,1) is just a slower way (in context) of executing t = randi(3) : the next q iteration, you could potentially get exactly the same t value again.

I calculate, for example, that if you ask for 5 different single-value random numbers, that roughly 39.5% of the time, at least one of the functions will not get executed. The more iterations, the lower the probability that a function will be missed, but the probability will never go to 0 if at least one iteration is done.

If you want to execute each function a minimum of a certain number of times, first construct a control vector that contains as many copies of the function index as the minimum number of executions. For example,

[1,1,2,3]

for the case where function 1 must be executed at least twice and functions 2 and 3 must be executed at least once each. Then append to that randi() of the number of functions, as many times as needed to fill out the iterations, so that after this step, the control vector is the same length as the total number of iterations. Now take

order = ControlVector(randperm(numel(ControlVector)));
for q = 1 : number_of_iterations
    t = order(q);
    switch t
        stuff
    end
end

This arrangement permits you to have different minimum number of iterations for the different functions.

If you just need to ensure that each function is executed at least once,then you can do

ControlVector = [1:NumberOfFunctions, randi(NumberOfFunctions, 1, number_of_iterations - number_of_functions)];
order = ControlVector(randperm(numel(ControlVector)));