1 #include <iostream> 2 #include <Eigen/Core> 3 4 using namespace Eigen; 5 6 #ifndef SCALAR 7 #define SCALAR float 8 #endif 9 10 #ifndef SIZE 11 #define SIZE 10000 12 #endif 13 14 #ifndef REPEAT 15 #define REPEAT 10000 16 #endif 17 18 typedef Matrix<SCALAR, Eigen::Dynamic, 1> Vec; 19 20 using namespace std; 21 22 SCALAR E_VDW(const Vec &interactions1, const Vec &interactions2) 23 { 24 return (interactions2.cwise()/interactions1) 25 .cwise().cube() 26 .cwise().square() 27 .cwise().square() 28 .sum(); 29 } 30 31 int main() 32 { 33 // 34 // 1 2 3 4 ... (interactions) 35 // ka . . . . ... 36 // rab . . . . ... 37 // energy . . . . ... 38 // ... ... ... ... ... ... 39 // (variables 40 // for 41 // interaction) 42 // 43 Vec interactions1(SIZE), interactions2(SIZE); // SIZE is the number of vdw interactions in our system 44 // SetupCalculations() 45 SCALAR rab = 1.0; 46 interactions1.setConstant(2.4); 47 interactions2.setConstant(rab); 48 49 // Energy() 50 SCALAR energy = 0.0; 51 for (unsigned int i = 0; i<REPEAT; ++i) { 52 energy += E_VDW(interactions1, interactions2); 53 energy *= 1 + 1e-20 * i; // prevent compiler from optimizing the loop 54 } 55 cout << "energy = " << energy << endl; 56 } 57
