How to minimize RAM utilization in GA Optimization tool ?

I want to use GA optimisation to minimise my function.

My main function , which I am using to minimise the quantity is:

function Z = WFD_optimization(para)

      global theta mu Ks y_bar A Omega Psi Mw Md ag eqt g yd;
      global tspan G dtt tResult xResult tf N_react t_react F_hor t_hor xw_abs aw_abs G_all;
      global  set_time stick_slip Fric_force; 

      angle = 20;
      Ks = para(1);
      pre_t = para(2);

      wedge_damper_input_v1                 %Read Input File
      theta = angle*pi()/180;               %wedge slope
      y_bar=pre_t/Ks;

      global A1 A2 B1 B2 C1 C2 Phi1 Phi2 Hpp Hpm Hmm Hmp  ;
      global count1 count2 count3 count4 count5 count6;

      dt = dtt;
      para = [theta;mu;E;I;L;Mw;Md;Ks;g;y_bar];
      tspan = 0:dt:tf ;

      tResult = [];
      xResult = [];

      [A1,A2,B1,B2,C1,C2,Psi,Phi1,Phi2,Hpp,Hpm,Hmm,Hmp] = get_const(para);

      G_dir = 'E:\IITB\MTP\MATLAB\New\Chevron v2\Results\Actual EQ\elcentro vibrationdata\Input\';
      G = earthquake_data(0.02,1/5,2,G_dir);
      PGA=max(abs(G(:,3)));

      eqn = 1;                        % Initial Equation
      count=0;

      while t0<tf-dtt

          [t,x] = wedge_inte(dt,eqn,t0,x0);
          if (sign(x(end,1)) ~= sign(x0(1,1)) && t0~=0)

              [eqn,t0,x0,dt] = y1_change(t0,x0,t,x,eps,dt,eqn);

          elseif sign(x(end,2)) ~= sign(x0(1,2))

              [eqn,t0,x0,dt] = y2_change(t0,x0,t,x,eps,dt,eqn);

          else
              t0 = t(end,1);   
              x0 = x(end, : );
              tResult = cat(1, tResult, t0);  
              xResult = cat(1, xResult, x0);

          end
      end

      Z(1) = max(abs(xResult(:,1)));
  %     Z(2) = max(abs());

end

Its uses several other functions to run.

I am using optimtool UI for optimization. My LB are [500 500] and UB are [15000 20000]. I kept the population size 10 and stopping criteria- generation at 10 , get results quicker for testing my algorithm.

The avg time required to run this algorithm (Not in optimization), just to optain 1 'Z' value is around 250 secs.

When I run GA optimization, It runs for a day , then it stops as MATLAB is irresponsive. The same error show memory utilization of about 14.9GB and my RAM is 16GB.

I have kept RAM utilization at 100%.

What exactly is the problem in this algorithm, why the full RAM is required? What changes can I do in this algorithm to get results on this same PC (RAM 16GB)?

Answer 1

[Alan Weiss]

Your problem seems to be optimizing parameters of an ODE. I have no idea why your code uses so much memory, because you didn't provide details about what your code does.

Nevertheless, I suggest that you try two things:

1. Use the MATLAB® performance and memory tools to help diagnose what is going on in your code.
2. Use patternsearch instead of ga for optimization. patternsearch is usually faster, more robust, and easier to tune than ga.

Good luck,

Alan Weiss

MATLAB mathematical toolbox documentation