Large Matrix Kron Reduction - How to transform below three nested loop to something faster

I'm trying to use Kron Reduction to reduce size of Ybus matrix. As the size of Ybus matrix increases to 1000 or more, the code is almost useless as it takes too much time. Is there a way I can use Parfor? Any other suggestion how to reduce calculation time?

tic
num=9241;
Ybus_temp = YbusAugmentation(num); %A function which modifies original Ybus matrix
L = num:-1:1;

          for s=L

              m = length(Ybus_temp);

              for i=1:m

                  for k = 1:m

                       if i~=s && k~=s

                         Ybus_temp(i,k) = Ybus_temp(i,k) - ((Ybus_temp(i,s)*Ybus_temp(s,k))/Ybus_temp(s,s));

                       end
                   end
              end

              Ybus_temp(s,:)=[];
              Ybus_temp(:,s)=[];

          end

Ybus_reduced=Ybus_temp;
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