82 lines
1.6 KiB
HolyC
82 lines
1.6 KiB
HolyC
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//Classic 2nd order nonlinear ordinary differential equation
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I64 mp_not_done_flags;
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#define OX 10
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#define OY GR_HEIGHT/2-FONT_HEIGHT
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#define MICRO_STEP 0.000001
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class State
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{
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F64 wabbits,hawks,
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d_wabbits,d_hawks; //Technically, these are not part of the state.
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};
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U0 Steps(State *s)
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{
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I64 i;
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for (i=0;i<10000;i++) {
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s->d_wabbits=s->wabbits*(1.0-0.10*s->hawks);
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s->d_hawks =-s->hawks *(1.0-0.01*s->wabbits);
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s->hawks +=s->d_hawks *MICRO_STEP;
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s->wabbits+=s->d_wabbits*MICRO_STEP;
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}
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}
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U0 PlotTrajectory(CTask *parent)
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{
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I64 i;
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CDC *dc=DCAlias(,parent);
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State s;
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MemSet(&s,0,sizeof(State));
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s.wabbits=RandU16%100 +10;
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s.hawks =RandU16%10 +1;
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for (i=0;i<1000;i++) {
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dc->color=LTGREEN;
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GrPlot(dc,s.wabbits+OX,OY-s.d_wabbits);
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dc->color=LTRED;
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GrPlot(dc,s.hawks +OX,OY-s.d_hawks);
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Steps(&s);
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}
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DCDel(dc);
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LBtr(&mp_not_done_flags,Gs->num);
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}
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U0 PredatorPrey()
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{
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I64 i;
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CDC *dc=DCAlias;
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PopUpOk("This will plot multiple predator-prey\n"
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"trajectories. It restarts many times\n"
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"with different, random, initial populations.\n");
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SettingsPush; //See $LK,"SettingsPush",A="MN:SettingsPush"$
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try {
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AutoComplete;
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WinBorder;
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WinMax;
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DocClear;
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Refresh;
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dc->color=BLACK;
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GrLine(dc,OX,0,OX,GR_HEIGHT-FONT_HEIGHT-1);
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GrLine(dc,0,OY,GR_WIDTH-1,OY);
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while (!ScanChar) {
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mp_not_done_flags=1<<mp_cnt-1;
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for (i=0;i<mp_cnt;i++)
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JobQue(&PlotTrajectory,Fs,i);
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do Yield;
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while (mp_not_done_flags);
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}
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} catch
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PutExcept;
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SettingsPop;
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DCFill(dc);
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DCDel(dc);
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}
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PredatorPrey;
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