course/semester2/pprog/assignment1/mthread/nbody.c

   1 /**
   2  * @file nbody.c
   3  * @author Sam Moore (20503628) 2012
   4  * @purpose N-Body simulator - Definition of simulation functions; single threaded version
   5  */
   6
   7 #include <stdlib.h>
   8 #include <stdio.h>
   9 #include <math.h>
  10 #include <time.h>
  11 #include <string.h>
  12 #include <stdbool.h>
  13
  14 #include "nbody.h"
  15
  16 /**
  17  * Prints the body on screen
  18  */
  19 void Body_Print(Body * a)
  20 {
  21         printf("Body %p M=%f X=%f Y=%f Z=%f Fx=%f Fy=%f Fz=%f Vx=%f Vy=%f Vz=%f\n",
  22            (void*)a, a->mass, a->x[0], a->x[1], a->x[2], a->F[0], a->F[1], a->F[2], a->v[0], a->v[1], a->v[2]);
  23 }
  24
  25 /**
  26  * Computing forces
  27  */
  28 void Body_Force(Body * a, System * s)
  29 {
  30         double distance;
  31         double con;
  32         double gd;
  33
  34         for (unsigned i = 0; i < DIMENSIONS; ++i)
  35                 a->F[i] = 0;
  36
  37         for (unsigned index = 0; index < s->N; ++index)
  38         {
  39                 Body * b = s->body+index;
  40                 if (b == a)
  41                         continue;
  42
  43                 distance = 0.0;
  44                 for (unsigned i = 0; i < DIMENSIONS; ++i)
  45                         distance += square(b->x[i] - a->x[i]);
  46                 distance = sqrt(distance);
  47                 con = G * a->mass * b->mass / square(distance);
  48                 gd = con / distance;
  49                 for (unsigned i = 0; i < DIMENSIONS; ++i)
  50                         a->F[i] += gd * (b->x[i] - a->x[i]);
  51         }
  52 }
  53
  54 /**
  55  * Compute velocities
  56  */
  57 void Body_Velocity(Body * a)
  58 {
  59         for (unsigned i = 0; i < DIMENSIONS; ++i)
  60                 a->v[i] += a->F[i] / a->mass * DELTA_T;
  61 }
  62
  63 /**
  64  * Compute positions
  65  */
  66 void Body_Position(Body * a)
  67 {
  68         for (unsigned i = 0; i < DIMENSIONS; ++i)
  69                 a->x[i] += a->v[i] * DELTA_T;
  70 }
  71
  72 /**
  73  * Main compute function
  74  */
  75 void System_Compute(System * s)
  76 {
  77 //      clock_t start, finish;
  78
  79 //      start = clock();
  80
  81         for (unsigned i = 0; i < s->N; ++i)
  82         {
  83                 Body_Force(s->body+i, s);
  84                 Body_Velocity(s->body+i);
  85                 Body_Position(s->body+i);
  86         }
  87
  88 }
  89
  90
  91
  92
  93 /*
  94  * This function reads an input file. You can change it if you choose a
  95  * different file format
  96  */
  97 #define LINE_SIZE BUFSIZ
  98 void System_Init(System * s, char *fileName)
  99 {
 100         char line[LINE_SIZE];
 101         char * token;
 102         FILE * file;
 103
 104         file = fopen(fileName, "rt");
 105         s->N = atoi(fgets(line, LINE_SIZE, file));
 106         s->body = (Body*) calloc((size_t)s->N, sizeof(Body));
 107
 108         //printf("----------------------Initial field-------------------------------\n");
 109
 110         for (unsigned i = 0; i < s->N; ++i)
 111         {
 112                 if (fgets(line, LINE_SIZE, file) != NULL)
 113                 {
 114                         Body * a = s->body+i;
 115                         token = strtok(line, ",; ");
 116                         a->mass = atof(token);
 117
 118                         for (unsigned j = 0; j < DIMENSIONS; ++j)
 119                         {
 120                                 token = strtok(NULL, ",; ");
 121                                 a->x[j] = atof(token);
 122                         }
 123                         for (unsigned j = 0; j < DIMENSIONS; ++j)
 124                         {
 125                                 token = strtok(NULL, ",; ");
 126                                 a->v[j] = atof(token);
 127                         }
 128                         //Body_Print(a);
 129                 }
 130         }
 131
 132         //printf("--------------------------------------------------------------\n");
 133
 134         fclose(file);
 135 }
 136
 137 /**
 138  * Cleans up the universe by freeing all memory
 139  */
 140 void Universe_Cleanup()
 141 {
 142         free(universe.body);
 143         pthread_exit(NULL);
 144 }
 145
 146 /**
 147  * Thread - Continuously computes steps for a system of bodies
 148  */
 149 void * Compute_Thread(void * s)
 150 {
 151         while (true)
 152         {
 153                 if (terminate) pthread_exit(NULL);
 154                 System_Compute((System*)s);
 155         }
 156 }
 157
 158
 159