# How to find where a very long code is stuck?

9 views (last 30 days)
Cantor Set on 19 Feb 2020
Edited: Adam Danz on 20 Feb 2020
This code is a part of coding a mutiobjective genetic algorithm, the algorithm for this code is as follows:
1. Initialization: Q=Ro; ND= ϕ, Ro is the initial population
2. Randomly select a row x of Q, and set Q=Q-{x} [here I mean remove the row x from Q], RK= ϕ , R= ϕ
3. while ( Q ϕ)
• for each y in Q do,
• if x dominates y, then remove y from Q and update Q {Q=Q-{y}}
• elseif, y dominates x then update x=y; and update Q by removing y from Q, Q=Q-{y}, RK=RK R then update R= ϕ [but since they are matrices so I use RK=[RK;R]; ]
• else, R= R {y} [I used R=[R;Y]; ], update Q by removing the row y from it
• end(if)
• end(do)
4. Take all the rows y in RK which are not dominated by x and put them in a matrix RKK
5.ND=[ND;x];
6.Q=[RKK;R];
7. If the number of rows in Q >1 then go to step 2, otherwise set ND=[ND;Q]; stop
in the code:
output=FD( x,y,Nvar,perci,Lb,Ub); is a function I wrote takes the rows/individuals x,y and returns 2 by Nvar*perci matrix named output, where the first row is the non-dominated individual and the second is the dominated one
Remark: In FD, 2 individuals/rows x,y has 3 outputs either x dominates y or y dominates x or no one dominates the other
in the first 2 cases FD returns: a matrix, 2 by Nvar*perci matrix named output, where the first row is the non-dominated individual and the second is the dominated one, in the third case it returns a matrix: output or 2 rows and Nvar*perci cols where each element in it is INF
I hope someone can help me because I am a beginner in MATLAB.
Thanks
Nind=100; %number of individuals to begin with
Nvar=1; %number of the decision variables
perci=10; %number of bits of every decision variable
Ro=crtbp(Nind,Nvar*perci); %random matrix of 0 and 1
%each element in it, is either 0 or 1
%crtbp is a function from GA toolbox
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function[Fronts,ranks]=IMPARENA(Nvar,perci,Ro,Lb,Ub)
iii=1; DOM=[]; ranks=[]; Lb=-100; Ub=100;
while ~isempty(Ro)
Q=Ro; carQ=size(Q,1);
ND=[];
while carQ>1
x=Q(1,:);
Q=Q(2:end,1:end); %remove x from Q
RK=[]; R=[]; RKK=[];
while ~isempty(Q) %while Q is not empty
y=Q(1,:); %let y be the first row in Q
output=FD( x,y,Nvar,perci,Lb,Ub); %check the dominance between y and x
if norm(x- output(1,1:end))==0 %if x dom y
%remove y from Q;
Q(all(Q==repmat(y,size(Q,1),1),2),:)=[];
elseif norm(y-output(1,1:end))==0 %if y dom x
x=y;
%remove y from Q
Q(all(Q==repmat(y,size(Q,1),1),2),:)=[];
RK=[RK;R]; R=[];
else
R=[R;y];
%remove y from Q
Q(all(Q==repmat(y,size(Q,1),1),2),:)=[];
end
if ~isempty(RK)
for j=1:size(RK,1)
rr=RK(j,1:end);
output=FD(x,rr,Nvar,perci,Lb,Ub);
if norm(x-output(1,1:end))~=0 %x~=output(1,1:end)
RKK=[RKK;rr];
else
j=j+1;
end
end
end
ND=[ND;x];
QSS=[RKK;R]; %%the code gets stuck here%%%
Q=QSS;
carQ=size(Q,1);
if carQ>1
break;
end
end
end
ND=[ND;Q];
%%%%%%%%%%%%%%%%%%%%%%%%%
UND=unique(ND, 'rows', 'stable');
ND=UND;
%%%%%%%%%%%
DOM=[DOM;ND];
%%%%%%
%assigning ranks
rD=iii*ones(size(ND,1),1);
ranks=[ranks;rD];
iii=iii+1;
%%%%%%%%%%%%%%%
C=setdiff(Ro,ND,'rows');
Ro=C;
end
%%%%%%%%%END%%%%%%%%%%%%
Fronts=[DOM];
ranks;
end
Matlab tell me that the error at the line I referred to but I don't understand why it tells me:
QSS is 1x10 double, RKK 0X0 empty double and R is 2x10 double
and that Q is empty 0x10 double!
Why? and what does it mean?
EDIT: The code sometimes work and sometimes it gets stuck, so maybe there is something computational that happens
because every time crtbp generates a different random binary matrix Ro
QSS=[RKK;R]; %it points that the problem is here
Q=QSS;
And it says that RKK is empty 0 x 0 double
QSS is empty 1 x 10 double
R is 2 x 10 double and that Q is 0 x 0 empty
Q is a matrix which changes its size through the loop
Adam Danz on 20 Feb 2020
Some methods to locate bottlenecks are
• use profile to time the function and produce a breakdown of execution times
• Within the inner most loop print the value of all loop iterations such as fprintf('i=%d, j=%d, k=%d\n', i,j,k)
• Step through the code in debug mode
• Strategically place tic/toc pairs throughout your code