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