step_gceom.h

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#ifndef STEP_GCEOM_H
#define STEP_GCEOM_H
 
#include <math.h>
#include "../../ascot5.h"
#include "../../math.h"
#include "../../physlib.h"
 
 
DECLARE_TARGET_SIMD
inline static void step_gceom(real* ydot, real* y, real mass, real charge,
                              real* B_dB, real* E) {
 
    real B[3];
    B[0] = B_dB[0];
    B[1] = B_dB[4];
    B[2] = B_dB[8];
 
    real normB = sqrt(math_dot(B, B));
    real gamma = physlib_gamma_ppar(mass, y[4], y[3], normB);
 
    real gradB[3];
    gradB[0] = (B[0]*B_dB[1] + B[1]*B_dB[5] + B[2]*B_dB[9]) / normB;
    gradB[1] = (B[0]*B_dB[2] + B[1]*B_dB[6] + B[2]*B_dB[10])
               / (normB * y[0]);
    gradB[2] = (B[0]*B_dB[3] + B[1]*B_dB[7] + B[2]*B_dB[11]) / normB;
 
    real gradBcrossB[3];
    math_cross(gradB, B, gradBcrossB);
 
    real curlB[3];
    curlB[0] = B_dB[10] / y[0] - B_dB[7];
    curlB[1] = B_dB[3] - B_dB[9];
    curlB[2] = (B[1] - B_dB[2]) / y[0] + B_dB[5];
 
    real Bstar[3];
    Bstar[0] = B[0] + (y[3] / charge)
                      * (curlB[0] / normB - gradBcrossB[0] / (normB*normB));
    Bstar[1] = B[1] + (y[3] / charge)
                      * (curlB[1] / normB - gradBcrossB[1] / (normB*normB));
    Bstar[2] = B[2] + (y[3] / charge)
                      * (curlB[2] / normB - gradBcrossB[2] / (normB*normB));
 
    real Estar[3];
    Estar[0] = E[0] - y[4] * gradB[0] / ( charge * gamma );
    Estar[1] = E[1] - y[4] * gradB[1] / ( charge * gamma );
    Estar[2] = E[2] - y[4] * gradB[2] / ( charge * gamma );
 
    real Bhat[3];
    Bhat[0] = B[0] / normB;
    Bhat[1] = B[1] / normB;
    Bhat[2] = B[2] / normB;
 
    real BhatDotBstar = math_dot(Bhat, Bstar);
 
    real EstarcrossBhat[3];
    math_cross(Estar, Bhat, EstarcrossBhat);
 
    ydot[0] = ( y[3] * Bstar[0] / ( gamma * mass )
                + EstarcrossBhat[0] ) / BhatDotBstar;
    ydot[1] = ( y[3] * Bstar[1] / ( gamma * mass )
                + EstarcrossBhat[1] ) / ( y[0]*BhatDotBstar );
    ydot[2] = ( y[3] * Bstar[2] / ( gamma * mass )
                + EstarcrossBhat[2] ) / BhatDotBstar;
    ydot[3] = charge * math_dot(Bstar,Estar) / BhatDotBstar;
    ydot[4] = 0;
    ydot[5] = charge * normB / ( gamma * mass );
 
}
 
 
#endif