102 lines
2.5 KiB
C++
102 lines
2.5 KiB
C++
#include <cstdio>
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#include <cmath>
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#include "de.h"
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// the order of the polynomial (actually the number of coefficients, i.e. 1 = constant, 2 = line, etc.)
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#define NUM_COEFFICIENTS 6
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// the function we're searching for
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double TargetFunction(double x)
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{
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return 1.0 / (1.0 + exp(-4.9*x)); // Ken Stanley's NEAT activation
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//return (1.0 / (1.0 + exp(-4.9*x)) - 0.5) * 2.0; // " " (signed version)
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//return (1.0 / (1.0 + exp(-x)) - 0.5) * 2.0; // signed sigmoid
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//return exp(-x*x); // gaussian
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//return tanh(x); // tanh
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//return (2.0/(1.0+exp(-x))-1.0); // tanh approximation
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//return (x<0.0 ? -1.0 : 1.0) * sqrt(abs(x)); // signed root
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//return sin(x); // sin
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}
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// a helper function used in calculating the polynomials
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double CalculatePolynomial(double x, int n_coeffs, const double coeffs[])
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{
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double accum = 0.0;
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double xmul = 1.0;
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for (int i = n_coeffs-1; i>=0; --i)
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{
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accum += xmul * coeffs[i];
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xmul *= x;
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}
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return accum;
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}
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// our DE implementation
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class PolySearch: public DE::Engine<NUM_COEFFICIENTS>
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{
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public:
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// this method is called by the DE::Engine::Solve() to test a single DE individual
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double CalculateError(const double testcase[NUM_COEFFICIENTS], bool& stop)
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{
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double error = 0.0;
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unsigned int test_count = 0;
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// accumulate squared error
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for ( double i=-7.9287;i<=7.9287;i+=0.001 )
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{
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// test
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double test = CalculatePolynomial(i,NUM_COEFFICIENTS,testcase);
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double actual = TargetFunction(i);
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// accumulate error^2
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double e = test - actual;
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error += e * e;
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// inc test count (divisor to get from SE to MSE)
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test_count++;
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}
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// convert SE to RMSE
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error = sqrt(error / (double)test_count);
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// set stop flag if the error is really low
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if ( error < 0.0000001 )
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{
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stop = true;
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}
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// done
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return error;
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}
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};
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// main program
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int main()
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{
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PolySearch de;
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// setup, adjust from default range
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de.SetRange(-0.1,0.1);
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// create new population with adjusted range
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de.Reset();
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// run the DE
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de.Solve(1000);
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// output winner in polynomial form
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printf("Best Polynomial Found\n=====================\ny =");
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for (int i=0;i<NUM_COEFFICIENTS-2;++i)
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{
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printf(" %0.16f*x^%d +",de.GetBest()[i],NUM_COEFFICIENTS-1-i);
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}
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printf(" %0.16f*x + %0.16f\n",de.GetBest()[NUM_COEFFICIENTS-2],de.GetBest()[NUM_COEFFICIENTS-1]);
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// done
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return 0;
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}
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