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1 #include<stdio.h>
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2 #include<stdlib.h>
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3 #include<unistd.h>
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4 #include<time.h>
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5 #include<SDL.h>
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6 #include<float.h>
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7
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8 #define DEBUGlog(f, args...) \
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9 ;
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10 //fprintf(stderr, "in %s: "f, __FUNCTION__, ## args)
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11
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12 #define W_HEIGHT 480
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13 #define W_WIDTH 640
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14
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15 /*
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16 N body problem
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17 */
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18
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19 static int NUM_BODY = 3;
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20 //static float Gravitation = 6.67e-11 ;
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21 //static float delta = 100;
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22 //static float FIELD = 2e11;
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23 static float Gravitation = 1.0f; // ?
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24 static float delta = 0.05f; //
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25 static float FIELD = 400.0f; // -100 ~ 100
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26 static const float eps = 1.5f;
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27
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28 typedef struct
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29 {
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30 /* star's parameter. */
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31 float weight;
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32 float a[3]; /* acceleration */
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33 float v[3]; /* velocity */
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34 float r[3]; /* position */
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35 /* for SDL. */
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36 SDL_Rect rect;
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37 } body;
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38 body *stars_old, *stars_new;
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39
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40 void start(void);
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41 __code initialize(int num);
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42 __code randomInit(SDL_Surface *screen, int num);
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43 __code starsInit(SDL_Surface *screen, int num);
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44 __code loop(int count, SDL_Surface *screen, int num);
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45 __code compute(int count, SDL_Surface *screen, int num);
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46 __code nextTurn(int count, SDL_Surface *screen, int num);
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47 __code moveCenter(int count, SDL_Surface *screen, int num);
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48 __code CenteringVelocity(int count, SDL_Surface *screen, int num);
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49
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50 int main(int argc, char **argv)
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51 {
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52 int ch;
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53 while ((ch = getopt(argc, argv, "s:g:")) != -1) {
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54 switch (ch) {
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55 case 's':
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56 delta = atof(optarg);
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57 break;
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58 case 'g':
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59 Gravitation = atof(optarg);
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60 break;
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61 case '?':
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62 default:
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63 break;
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64 }
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65 }
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66 start();
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67 return 0;
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68 }
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69 void start()
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70 {
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71 goto initialize(NUM_BODY);
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72 }
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73
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74 __code finish(int ret)
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75 {
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76 DEBUGlog("Gravity = %e\n", Gravitation);
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77 DEBUGlog("FLT_MAX = %e\n", FLT_MAX);
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78 DEBUGlog("FLT_MAX_EXP = %d\n", FLT_MAX_EXP);
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79 DEBUGlog("FLT_MIN = %e\n", FLT_MIN);
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80 DEBUGlog("FLT_MIN_EXP = %d\n", FLT_MIN_EXP);
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81 DEBUGlog("FLT_EPSILON = %e\n", FLT_EPSILON);
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82 free(stars_old);
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83 free(stars_new);
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84 exit(ret);
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85 }
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86
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87
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88 __code initialize(int num)
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89 {
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90 SDL_Surface *screen;
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91
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92 /* malloc. */
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93 stars_old = malloc( sizeof(body)*num );
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94 stars_new = malloc( sizeof(body)*num );
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95 if (stars_old==NULL||stars_new==NULL){
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96 perror("malloc");
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97 goto finish(1);
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98 }
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99
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100 /* SDL initialization. */
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101 if(SDL_Init(SDL_INIT_VIDEO) < 0){ //Could we start SDL_VIDEO?
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102 fprintf(stderr,"Couldn't init SDL"); //Nope, output to stderr and quit
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103 exit(1);
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104 }
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105 screen = SDL_SetVideoMode(W_WIDTH, W_HEIGHT, 32, SDL_HWSURFACE | SDL_RESIZABLE); //Create a 640x480x32 resizable window
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106 atexit(SDL_Quit); //Now that we're enabled, make sure we cleanup
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107
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108 goto starsInit(screen, num);
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109 }
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110
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111 __code starsInit0(SDL_Surface *screen, int num)
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112 {
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113 int i;
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114 srandom(time(NULL));
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115 for (i=0; i<num; i++){ // this loop should be split into few code segment..
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116 stars_old[i].weight = random()/(RAND_MAX+1.0)*5+5;
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117 stars_old[i].v[0] = random()/(RAND_MAX+1.0)*5+5;
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118 stars_old[i].v[1] = random()/(RAND_MAX+1.0)*5+5;
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119 stars_old[i].v[2] = random()/(RAND_MAX+1.0)*5+5;
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120 stars_old[i].r[0] = random()/(RAND_MAX+1.0)*5+5;
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121 stars_old[i].r[1] = random()/(RAND_MAX+1.0)*5+5;
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122 stars_old[i].r[2] = random()/(RAND_MAX+1.0)*5+5;
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123 stars_new[i].weight = stars_old[i].weight;
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124 }
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125
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126 goto loop(0, screen, num);
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127 }
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128 __code starsInit(SDL_Surface *screen, int num)
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129 {
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130 int i;
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131 #if 0
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132 /* */
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133 stars_old[0].weight = 110;
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134 stars_old[0].v[0] = 0.0;
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135 stars_old[0].v[1] = -1.0;
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136 stars_old[0].v[2] = 0.0;
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137 stars_old[0].r[0] = 100.0;
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138 stars_old[0].r[1] = 0.0;
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139 stars_old[0].r[2] = 0.0;
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140 /* */
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141 stars_old[1].weight = 110;
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142 stars_old[1].v[0] = 0.0;
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143 stars_old[1].v[1] = -1.0;
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144 stars_old[1].v[2] = 0.0;
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145 stars_old[1].r[0] = -100.0;
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146 stars_old[1].r[1] = 0.0;
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147 stars_old[1].r[2] = 0.0;
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148 /* */
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149 stars_old[2].weight = 110;
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150 stars_old[2].v[0] = -1.0;
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151 stars_old[2].v[1] = 0.0;
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152 stars_old[2].v[2] = 0.0;
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153 stars_old[2].r[0] = 0.0;
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154 stars_old[2].r[1] = 0.0;
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155 stars_old[2].r[2] = -70.0;
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156 #else
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157 /* */
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158 stars_old[0].weight = 100;
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159 stars_old[0].v[0] = -1.0;
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160 stars_old[0].v[1] = 0.0;
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161 stars_old[0].v[2] = 0.5;
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162 stars_old[0].r[0] = 50.0;
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163 stars_old[0].r[1] = 0.0;
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164 stars_old[0].r[2] = 0.0;
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165 /* */
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166 stars_old[1].weight = 100;
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167 stars_old[1].v[0] = -0.5;
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168 stars_old[1].v[1] = 0.1;
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169 stars_old[1].v[2] = 1.732;
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170 stars_old[1].r[0] = -50.0;
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171 stars_old[1].r[1] = 0.0;
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172 stars_old[1].r[2] = 0.0;
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173 /* */
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174 stars_old[2].weight = 100;
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175 stars_old[2].v[0] = 0.5;
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176 stars_old[2].v[1] = -0.1;
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177 stars_old[2].v[2] = -1.732;
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178 stars_old[2].r[0] = 0.0;
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179 stars_old[2].r[1] = 0.0;
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180 stars_old[2].r[2] = 86.60;
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181 #endif
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182
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183 for( i=0; i<num; i++){
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184 stars_new[i].weight = stars_old[i].weight;
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185 stars_new[i].rect.h = 5, stars_new[i].rect.w = 5;
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186 stars_old[i].rect.h = 5, stars_old[i].rect.w = 5;
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187 }
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188
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189 goto loop(0, screen, num);
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190 }
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191
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192 __code starsInit1(SDL_Surface *screen, int num)
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193 {
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194 int i;
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195 /* Sun */
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196 stars_old[0].weight = 1.9891e30; // 1.9891*10^30
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197 stars_old[0].v[0] = 0.0;
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198 stars_old[0].v[1] = 0.0;
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199 stars_old[0].v[2] = 0.0;
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200 stars_old[0].r[0] = 0.0;
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201 stars_old[0].r[1] = 0.0;
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202 stars_old[0].r[2] = 0.0;
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203 /* Venus */
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204 stars_old[1].weight = 4.869e24; // 4.869*10^24
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205 stars_old[1].v[0] = 0.0;
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206 stars_old[1].v[1] = 3.50214e4; // 35.0214 km/s
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207 stars_old[1].v[2] = 0.0;
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208 stars_old[1].r[0] = 1.08e11; // 108,208,930 km
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209 stars_old[1].r[1] = 0.0;
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210 stars_old[1].r[2] = 0.0;
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211 /* Earth */
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212 stars_old[2].weight = 5.9742e24; // 5.9742*10^24
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213 stars_old[2].v[0] = 0.0;
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214 stars_old[2].v[1] = 2.97859e4; // 29.7859 km/s
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215 stars_old[2].v[2] = 0.0;
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216 stars_old[2].r[0] = 1.49e11; // 149,597,870km
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217 stars_old[2].r[1] = 0.0;
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218 stars_old[2].r[2] = 0.0;
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219
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220 for( i=0; i<num; i++){
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221 stars_new[i].weight = stars_old[i].weight;
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222 stars_new[i].rect.h = 5, stars_new[i].rect.w = 5;
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223 stars_old[i].rect.h = 5, stars_old[i].rect.w = 5;
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224 }
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225
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226 goto loop(0, screen, num);
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227 }
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228
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229 __code loop(int count, SDL_Surface *screen, int num)
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230 {
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231 SDL_Event event;
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232
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233 /* check SDL event. */
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234 while(SDL_PollEvent(&event)){ //Poll events
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235 switch(event.type){ //Check event type
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236 case SDL_QUIT: //User hit the X (or equivelent)
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237 goto finish(1);
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238 //case SDL_VIDEORESIZE: //User resized window
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239 //screen = SDL_SetVideoMode(event.resize.w, event.resize.h, 32,
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240 //SDL_HWSURFACE | SDL_RESIZABLE); // Create new window
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241 //break; //Event handled, fetch next :)
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242 case SDL_KEYDOWN:
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243 if (event.key.keysym.sym==SDLK_UP && event.key.state==SDL_PRESSED)
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244 FIELD *= 2.0;
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245 else if (event.key.keysym.sym==SDLK_DOWN && event.key.state==SDL_PRESSED)
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246 FIELD /= 2.0;
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247 else if (event.key.keysym.sym==SDLK_r && event.key.state==SDL_PRESSED)
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248 goto moveCenter(count, screen, num);
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249 else if (event.key.keysym.sym==SDLK_v && event.key.state==SDL_PRESSED)
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250 goto CenteringVelocity(count, screen, num);
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251 break;
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252 default:
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253 break;
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254 } //Finished with current event
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255 } //Done with all events for now
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256
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257 if ( count<num ){
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258 DEBUGlog("count %d, goto commpute().\n", count);
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259 goto compute(count, screen, num);
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260 }else{
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261 DEBUGlog("count %d, goto nextTurn()\n", count);
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262 goto nextTurn(count, screen, num);
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263 }
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264 }
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265
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266 __code CenteringVelocity(int count, SDL_Surface *screen, int num)
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267 {
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268 int i;
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269 float v0,v1,v2;
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270 v0=v1=v2=0.0;
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271
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272 for (i=0; i<num; i++){
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273 v0 += stars_old[i].v[0];
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274 v1 += stars_old[i].v[1];
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275 v2 += stars_old[i].v[2];
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276 }
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277 v0/=(float)num; v1/=(float)num; v2/=(float)num;
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278 for (i=0; i<num; i++){
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279 stars_old[i].v[0] -= v0;
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280 stars_old[i].v[1] -= v1;
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281 stars_old[i].v[2] -= v2;
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282 }
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283
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284 goto loop(0, screen, num);
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285 }
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286 __code moveCenter(int count, SDL_Surface *screen, int num)
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287 {
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288 int i;
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289 float m0,m1,m2;
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290 m0=m1=m2=0.0;
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291
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292 for (i=0; i<num; i++){
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293 m0 += stars_old[i].r[0];
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294 m1 += stars_old[i].r[1];
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295 m2 += stars_old[i].r[2];
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296 }
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297 m0/=(float)num; m1/=(float)num; m2/=(float)num;
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298 for (i=0; i<num; i++){
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299 stars_old[i].r[0] -= m0;
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300 stars_old[i].r[1] -= m1;
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301 stars_old[i].r[2] -= m2;
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302 }
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303
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304 goto loop(0, screen, num);
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305 }
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306
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307 /*
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308 * next x = x+dx
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309 * dx = v*dt => dx/dt = v
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310 * dv = a*dt => dv/dt = a
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311 * a = F/m;
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312 * F = F1 + F2 + ... + Fn
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313 * Fi = G m1m2/r^2
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314 *
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315 */
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316 __code compute(int count, SDL_Surface *screen, int num)
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317 {
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318 int i;
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319 /* a is accel this planet receive now. */
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320 stars_old[count].a[0]=stars_old[count].a[1]=stars_old[count].a[2]=0.0f;
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321 DEBUGlog("count=%d\n", count);
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322 for (i=0; i<num; i++){ // this loop should be split to few code segment..
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323 //float F;
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324 float d0, d1, d2, d;
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325 float a;
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326 //body *o, *m;
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327 //o = &stars_old[i]; m = &stars_old[count];
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328
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329 /* skip compute with itself. */
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330 if ( i==count ) continue;
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331 /* compute distance between two i-th planet and itself. */
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332 d0 = stars_old[i].r[0] - stars_old[count].r[0];
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333 d1 = stars_old[i].r[1] - stars_old[count].r[1];
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334 d2 = stars_old[i].r[2] - stars_old[count].r[2];
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335 d = ( d0*d0+d1*d1+d2*d2+eps*eps );
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336 /* compute force it receive from i-th planet. */
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337 //F = Gravitation * stars_old[i].weight * stars_old[count].weight / d;
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338 /* and accel. */
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339 //a = F/stars_old[count].weight;
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340 a = Gravitation/d * stars_old[i].weight ;
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341 stars_old[count].a[0] += a*d0/sqrt(d);
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342 stars_old[count].a[1] += a*d1/sqrt(d);
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343 stars_old[count].a[2] += a*d2/sqrt(d);
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344 DEBUGlog("a=%e, d=%e, d0=%e\n", a, d, d0);
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345 DEBUGlog("g*w=%e\n", Gravitation*stars_old[i].weight);
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346 }
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347
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348 stars_new[count].v[0] = stars_old[count].v[0]+stars_old[count].a[0]*delta;
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349 stars_new[count].v[1] = stars_old[count].v[1]+stars_old[count].a[1]*delta;
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350 stars_new[count].v[2] = stars_old[count].v[2]+stars_old[count].a[2]*delta;
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351 stars_new[count].r[0] = stars_old[count].r[0]+stars_new[count].v[0]*delta/*+stars_old[count].a[0]*delta*delta/2.0*/;
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352 stars_new[count].r[1] = stars_old[count].r[1]+stars_new[count].v[1]*delta/*+stars_old[count].a[1]*delta*delta/2.0*/;
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353 stars_new[count].r[2] = stars_old[count].r[2]+stars_new[count].v[2]*delta/*+stars_old[count].a[2]*delta*delta/2.0*/;
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354
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355 stars_new[count].rect.x = (stars_new[count].r[0]*(float)W_HEIGHT/FIELD/2)+(W_WIDTH/2);
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356 stars_new[count].rect.y = (stars_new[count].r[1]*(float)W_HEIGHT/FIELD/2)+(W_HEIGHT/2);
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357 DEBUGlog("x = %e, x=%d\n", stars_new[count].r[0], stars_new[count].rect.x);
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358 DEBUGlog("y = %e, y=%d\n", stars_new[count].r[1], stars_new[count].rect.y);
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359 DEBUGlog("z = %e\n", stars_new[count].r[2]);
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360 DEBUGlog("vx = %e\n", stars_new[count].v[0]);
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361 DEBUGlog("vy = %e\n", stars_new[count].v[1]);
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362 DEBUGlog("vz = %e\n", stars_new[count].v[2]);
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363 DEBUGlog("a0=%e,a1=%e,a2=%e\n", stars_new[count].a[0], stars_new[count].a[1], stars_new[count].a[2]);
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364 DEBUGlog("x=%d,y=%d,h=%d,w=%d\n",stars_old[count].rect.x,stars_old[count].rect.y,stars_old[count].rect.h,stars_old[count].rect.w);
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365 SDL_FillRect(screen, &stars_old[count].rect, SDL_MapRGB(screen->format, 0x00,0x00,0x00));
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366 SDL_FillRect(screen, &stars_new[count].rect, SDL_MapRGB(screen->format, 0xff,0x88,0x33));
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367 //SDL_BlitSurface(screen, &stars_old[count].rect, screen, &stars_new[count].rect);
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368
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369 goto loop(++count, screen, num);
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370 }
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371
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372 /* it is executed after all bodies parameter is computed. */
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373 __code nextTurn(int count, SDL_Surface *screen, int num)
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374 {
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375 body *tmp;
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376 tmp = stars_old;
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377 stars_old = stars_new;
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378 stars_new = tmp;
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379 SDL_UpdateRect(screen, 0, 0, 0, 0);
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380
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381 goto loop(0, screen, num);
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382 }
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383
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384
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385
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386 /*
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387 +--------+-----------+
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388 | v |
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389 | +-----------+ |
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390 | | loop | |
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391 | +-----+-----+ |
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392 | | |
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393 | +-----v-----+ |
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394 | + compute +-----+
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395 | +-----+-----+ count++
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396 | |
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397 | | count==num
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398 | +-----v-----+
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399 | | nextTurn |
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400 | +-----+-----+
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401 | | count=0
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402 +--------+
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403 */
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404
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405
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406
|
