Implementing parallel while loops in matlab.

Hi all,

I am writing code that has two while loops in a random sampling exercise. I have two questions.

I would like the while loops to be performed simultaneously as opposed to the nested loops below, which does not yield the desired results. How can one modify the code to perform a parallel while loop/ simultaneously sample each of the while loops? And secondly, how can I pass the DG_uptake and DG2_uptake variables into one variable in the while loop as opposed to obtaining each one of them separately? Thank you.

while (modules_DG>=1) % number of DG

DG_PoC=randsample(MCS_nodes,1,true) % randomly select the position of DG1

while modules_DG2>=1 % number of DG2

DG2_PoC=randsample(MCS_nodes_DG2,1,true) % random selection of DG2 position

if rem(DG2_PoC,3)==0

DG2_node_pos=fix(DG2_PoC/3);

DG2_phase_pos=3;

else

DG2_phase_pos=rem(DG2_PoC,3);

DG2_node_pos=fix(DG2_PoC/3)+1;

end

DG2_uptake(DG2_node_pos,DG2_phase_pos) = DG2_uptake(DG2_node_pos,DG2_phase_pos)+ 1

if DG2_uptake(DG2_node_pos,DG2_phase_pos)> DG2_modules(DG2_node_pos,DG2_phase_pos)

DG2_uptake(DG2_node_pos,DG2_phase_pos) = DG2_uptake(DG2_node_pos,DG2_phase_pos)- 1

remove_PoC = MCS_nodes_DG2== (DG2_node_pos - 1)*3 + DG2_phase_pos; %determine the full PoC

MCS_nodes_DG2(remove_PoC) = [];%remove node from allocation array

else

modules_DG2=modules_DG2-1;

end

end

if rem(DG_PoC,3)==0

DG_node_pos=fix(DG_PoC/3);

DG_phase_pos=3;

else

DG_phase_pos=rem(DG_PoC,3);

DG_node_pos=fix(DG_PoC/3)+1;

end

DG_uptake(DG_node_pos,DG_phase_pos) = DG_uptake(DG_node_pos,DG_phase_pos)+ 1;

if DG_uptake(DG_node_pos,DG_phase_pos)> DG_modules(DG_node_pos,DG_phase_pos)

DG_uptake(DG_node_pos,DG_phase_pos) = DG_uptake(DG_node_pos,DG_phase_pos)- 1

remove_PoC = MCS_nodes== (DG_node_pos - 1)*3 + DG_phase_pos; %determine the full PoC

MCS_nodes(remove_PoC) = [];%remove node from allocation array

else

modules_DG = modules_DG - 1

end

end

[MarKf]

The variable modules at the end should probably be the one designated as modules_DG. The nested DG2 while-loop does not seem to depend on any variable defined in the main DG one and viceversa. This seems the result of some quick and dirty distracted code duplication/addition/editing, since it seems there are no differences between the 2 loops.

You could then, yes, easily separate (while, end; while, end) or integrate (while,DG(1,:),DG(2,:),end or while,for dgi=1:2,end,end) them. You'd have to put together any variables which have the 2 versions DG and DG2, also outside the loop that we see hjere, if they are matrices or cells that's easy, just add a dimension (e.g DG_node_pos(1,:)= fix(DG_PoC(1,:)/3);) otherwise you could use a struct (e.g DG_variable.(['dg' dgi])).

[Lewis Waswa]

The two loops perform the same function, hence the duplication. The thing is modules_DG and modules DG2 are not of the same length and are different. I would like to know if these two loops can be re-written to be implemented simulatneously. You are also right, I edited the code significantly but I hope one gets the idea of random sampling of two variables by implementing a while loop. @Marco Fuscà, your first suggestion gives me the same results as the above nested code, and therefore not very helpful.

[MarKf]

if the length of modules_DG and modules_DG2, which are used to define the while loops, are different, one would need to know how they differ and which is the logic to create them to ascertain whether you could integrate them or not, sice they are defined outside of the loop and we have no way of knowing how and if this code runs.

It's likely you can only do it separately (if by simultaneously you mean together in the same while loop that is, otherwise you can parfor, that's real simultaneity) that is while, DG, end; while, DG2, end then. Just copy and paste the nested DG2 while loop ouside, otherwise you are repeating that nested one a lot needlessly.

[Lewis Waswa]

Thanks for your input @Marco Fuscà. I appreciate