[Bf-committers] Random IPO Generator

Reuben Martin reuben.m at gmail.com
Sat Jan 14 19:04:59 CET 2006

On 1/12/06, Reuben Martin <reuben.m at gmail.com> wrote:
> On 1/10/06, Yann Vernier <yann at donkey.dyndns.org> wrote:
> > On Tue, 10 Jan 2006 14:05:20 -0600
> > Reuben Martin <reuben.m at gmail.com> wrote:
> >
> > > I hope the following "sudo-code" will give an idea of what I'm talking
> > > about. (Yes, it's awful, but I haven't written serious code in almost
> > > 10 years)
> > <snip>
> > > Hope that gives the "general idea" of how the randomness would be
> > > controlled.
> >
> > That would be pseudo code.
> Ack. Too much use of "su" within my shell...
> >In this case, it's very nearly C99.. if you
> > just typedef int var; it basically works. But the algorithm in there is
> > a simple capped line, not at all random. I think you're looking more
> > for a randomly varying step size for a fairly smooth curve, or just
> > random values for a wilder one.
> Well the cap is just for setting limits.  If you'll take a closer look
> the use of a random bool function will control weather or not the
> curve moves up or down. The momentum determines how often the curve
> has the chance to change directions. I'm thinking there should also be
> a way to add jitter in there somewhere, but haven't quite figured out
> where that would fit in.

I realize now why you said this is just a caped line. I had implied
that this algorithm would be inside of a loop, but never explicitly
said so in the email. So maybe this would make more sense:

var max_ipo_value;      //sets upper limit for the IPO
var min_ipo_value;      //sets lower limit for the IPO
var ipo_value;          //the value that the random IPO key will have
var ipo_time;           //the time at which the random IPO key will be placed
var speed;              //the higher the value, the slower the IPO curves move
var momentum;           //the lower the value, the more erratic the
IPO curves are
var step_sze;           //the higher the value, the steeper the slope
of the IPO curves
var start_time          // where in the time line to start generating IPO values
var stop_time          //where in time line to stop generating IPO values

//start out between the min and max
ipo_value := min_ipo_value + ((max_ipo_value - min_ipo_value) / 2)
ipo_time := start_time
set_ipo_key (ipo_value, ipo_time)

//start the loop

while (ipo_time < stop_time) do {
       direction := generate_random_bool();

       if (direction = true) then {
              for (i = 0, i < momentum, i++) do {
                      ipo_value += step_size;
                      if (ipo_value > max_ipo_value) then ipo_value =
                      ipo_time += speed;
                      set_ipo_key (ipo_value, ipo_time);

       else {
              for (i = 0, i < momentum, i++) do {
                      ipo_value -= step_size;
                      if (ipo_value < min_ipo_value) then ipo_value =
                      ipo_time += speed;
                      set_ipo_key (ipo_value, ipo_time);

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