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dyndiff.C

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//.............................................................................
//    version 1:  Nov 1993   Piet Hut              email: piet@guinness.ias.edu
//                           Institute for Advanced Study, Princeton, NJ, USA
//.............................................................................
//  non-local function: 
//    dyndiff
//.............................................................................

#include "dyn.h"

#ifdef TOOLBOX

//-----------------------------------------------------------------------------
//  dyndiff  --  determine the rms difference between the 6N coordinates of
//               two N-body systems
//               NOTE: simple version for flat tree only.
//-----------------------------------------------------------------------------

real  dyndiff(dyn * b1, dyn * b2, bool r_flag)
{
    //  quick fix to determine  n  for a flat tree:

    int  n1, n2;
    dyn * bi1;
    dyn * bi2;
    for (n1 = 0, bi1 = b1->get_oldest_daughter(); bi1 != NULL;
         bi1 = bi1->get_younger_sister())
        n1++;
    for (n2 = 0, bi2 = b2->get_oldest_daughter(); bi2 != NULL;
         bi2 = bi2->get_younger_sister())
        n2++;
    if (n1 != n2)
        {
        cerr << "dyndiff: N1 = " << n1 << " != N2 = " << n2 << endl;
        exit(1);
        }

    real sum_sq_diff = 0;     // sum of the squares of the 6N differences

    for (bi1 = b1->get_oldest_daughter(), bi2 = b2->get_oldest_daughter();
         bi1 != NULL;
         bi1 = bi1->get_younger_sister(), bi2 = bi2->get_younger_sister())
        {
        vector  dr = bi1->get_pos() - bi2->get_pos();
        sum_sq_diff += dr*dr;
        
        if (!r_flag)
            {
            vector  dv = bi1->get_vel() - bi2->get_vel();
            sum_sq_diff += dv*dv;
            }
        }

    if (r_flag)
        return sqrt(sum_sq_diff / (3 * n1));
    else
        return sqrt(sum_sq_diff / (6 * n1));
}

main(int argc, char ** argv)
{
    bool  r_flag = FALSE;      // if TRUE: check only spatial differences

    check_help();

    extern char *poptarg;
    int c;
    char* param_string = "r";

    while ((c = pgetopt(argc, argv, param_string)) != -1)
        switch(c) {

            case 'r': r_flag = TRUE;
                      break;
            case '?': params_to_usage(cerr, argv[0], param_string);
                      get_help();
                      exit(1);
        }            

    dyn * b1;
    dyn * b2;
    b1 = get_dyn(cin);
    b2 = get_dyn(cin);

    real  rmsdiff = dyndiff(b1, b2, r_flag);

    if (r_flag)
        cout << "  rms configuration space differences per coordinate:   "
             << rmsdiff << endl;
    else
        cout << "  rms phasespace differences per coordinate:   "
             << rmsdiff << endl;
}

#endif

// endof: dyndiff.C

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