/*   nbody hints
 */

#include <stdio.h>
#include <stdlib.h>

   /*  command line default options and arguments
    */
   double dT=1.0;	 /* delta-t 				*/
   double  G=1.0;	 /* gravitational constant 	 	*/
   int maxiter=1;	 /* iterations to termination 		*/
   char *fin="in.mat";	 /* input file name 			*/
   char *fout="out.mat"; /* output file name			*/
   int bm=0;		 /* produce a bitmap every b iter's 	*/
   int vx=0, vy=0, vz=0; /* select the view plane		*/
   int s=0;		 /* ignore the s most distant objects 	*/

   extern char *optarg;
   extern int optind, opterr, optopt;

   while ((i = getopt(argc, argv, "t:g:q:i:o:b:xyzs:")) != EOF)
     switch (i) {
       case 't':
	 dT = atof(optarg);
	 break;
       case 'g':
	 G = atof(optarg);
	 break;
       case 'q':
	 maxiter = atoi(optarg);
	 break;
       case 'i':
	 fin = malloc(strlen(optarg));
	 strcpy(fin, optarg);
	 break;
       case 'o':
	 fout = malloc(strlen(optarg));
	 strcpy(fout, optarg);
	 break;
       case 'b':
	 bm = atoi(optarg);
	 break;
       case 'x': vx = 1; break;
       case 'y': vy = 1; break;
       case 'z': vz = 1; break;
       case 's':
	 s = atoi(optarg);
	 break;
       case 'h':
       case '?':
	 fprintf(stderr, "nbody: bad argument %s\n", optarg);
	 exit(1);
	 break;
	 }


  /*  option to display bodies
   *  (from sequential nbody code)
   */
  if (bm && k % bm == 0) {
     for (i=0; i<numbod; i++)
	if (xmin <= x[i] && x[i] <= xmax &&
	    ymin <= y[i] && y[i] <= ymax) {

	   xpix = trunc(256.0 * (x[i]-xmin)/(xmax-xmin));
	   ypix = trunc(256.0 * (y[i]-ymin)/(ymax-ymin));

	   d = image[xpix][ypix];
	   d += 126 * (M[i]-minmass) / (maxmass-minmass) + 1;
	   image[xpix][ypix] = (d > 127) ? 127 : d;
	   }