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C/C++ Source or Header  |  1989-11-18  |  470 b   |  23 lines
  1. /*
  2. ### symplectic Ruth integration (First order, explicit) ###
  3. */
  4.  
  5. symp_ruth_int_one(vx1,vx,ptime,time_step,dim)
  6. double vx1[],vx[],*ptime,time_step;
  7. int dim;
  8. {
  9.     int i;
  10.     extern int model;
  11.     extern double *t_vf,*param;
  12.     extern int (*f_p)();
  13.  
  14.     
  15.     (int) f_p(vx1,1,vx,param,*ptime,dim);
  16.     for(i=0;i<dim;i += 2)
  17.         vx1[i] = vx[i] + time_step * vx1[i];
  18.     (int) f_p(t_vf,2,vx1,param,*ptime,dim);
  19.     for(i=1;i<dim;i += 2)
  20.         vx1[i] = vx[i] + time_step * t_vf[i];
  21.     *ptime += time_step;
  22. }
  23.