/*--- leap: takes a leapfrog step ---*/
double leap(CHAIN * C, double h)
{
double dTdP[C->N-1][3], dUdQ[C->N-1][3], du1[C->N-1][3], du2[C->N-1][3], T, a1, a0, U, Pt = -(C->E);
//set up to calculate Q_1/2
T = calc_T(C);
a0 = 1/(2.0*(T + Pt));
calc_dT(C,dTdP);
mat_scalar_mult(C->N-1,3,dTdP,h*a0,dTdP); //multiplied dTdP by scalar a
mat_add(C->N-1,3,C->R,dTdP,C->R); //this has updated C->R to equal Q_1/2
//calculate P_1
calc_dU1(C,du1);
calc_dU2(C,du2);
mat_add(C->N-1,3,du1,du2,dUdQ);
U = calc_U(C);
mat_scalar_mult(C->N-1,3,dUdQ, -h/U ,dUdQ); //multiplied dUdQ by scalar -h/U
mat_add(C->N-1,3,C->W,dUdQ,C->W); //this has updated C->W to equal P_1
//set up to calculate Q_1
T = calc_T(C);
a1 = 1/(2.0*(T + Pt));
calc_dT(C,dTdP);
mat_scalar_mult(C->N-1,3,dTdP,h*a1,dTdP); //multiplied dTdP by scalar a
mat_add(C->N-1,3,C->R,dTdP,C->R); //this has updated C->R to equal Q_1/2
return h/2.0 * (a1 + a0); //returns update for time value, so use t += leap(C,h);
}
int main(int argc, char* argv[])
{
struct marsopts opts = init(argc, argv);
Agraph_t* g = agread(opts.fin, (Agdisc_t*)NULL);
Agnode_t* n;
mat z;
init_graph(g);
z = mars(g, opts);
mat_scalar_mult(z, opts.scale);
if(opts.viewer) {
viewer(argc, argv);
} else {
for(n = agfstnode(g); n; n = agnxtnode(g,n)) {
int id = getid(n);
char* s = pos_to_str(&z->m[mindex(id, 0, z)], z->c);
agset(n,"pos",s);
free(s);
}
agwrite(g, opts.fout);
}
mat_free(z);
clean_up(g);
agclose(g);
return 0;
}
