It is necessary to reset (initialize) the weights during the learning period??

I am working on forecasting of radiation solar by Matlab and I have just beginner’s expertise with the program. it is necessary to reset (initialize) the weights during the learning period to determine the number of hidden layer neurons ? How I can do it? What is the command? this is a part of my program :

please Where can I put the command to reset the weights ???!

n=50; % number of epochs

net=fitnet(NNHL)      % NNHHL: number of nodes in hiden layer

        for NNHL=1:15 

          net.layers{1}.dimensions=NNHL;

      fprintf('number of nodes is :%d\n',NNHL);

             for j=1:1:n % n: number of epochs 

                 [net,tr] = train(net,inputs,targets);
                 outputs = net(inputsTesting);
                 perf = mse(net,targetsTesting,outputs);

           end 
        end

best regards