Re: fractional time values in an integer Schedule (sort of)

[cal]

hihi, all -

i would do something different from what alex suggested (which was to make an
integer time scale at a smaller unit)

the problem seems to me to be how to send out an integer number of packets
when the computed rate is not an integer (e.g., 2.43) -

first, i would take the integer part of the number (i.e., 2) and send out 2
packets in the usual way

then, i would take the fractional part of the number (0.43), and, with
probability 0.43, send out one more packet

in the long run, it makes the rates work exactly rather than approximately (so
if that doesn't matter very much, alex's method is much simpler)

finally, i would record the actual values for the number of packets sent, and
use it to backcompute F() for instrumentation purposes - if the resulting time
history or distribution of F() values is unreasonable, then there is a
sensitivity in the model that needs to be examined

more later,
cal


> Hi,
>
> In my simulation, I have some source nodes in a network (TCP-like) which
> send out discrete packets, and the sources also update their source rates
> x(t) (packets/timestep) according to an adaptive rule
>
> x(t+1) = x(t) +  k*F( )
>
> where k is a "gain" parameter and F( ) is a function which returns an
> integer.
>
> Since x(t) is the number of packets which a source emits in one simulation
> time step, then the this number must be an integer.
>
> However, I need to have a fractional gain parameter, k, which may also
> be interpreted as a "learning rate". Currently, I am constrained to having
> integer values of k, but even k=1 is way too large for my purposes
> (oscillations, etc.)
>
> If x(t) were to be defined as a FLOAT instead of an INT, then what
> scheduling mechanism could deal with say, 2.5 packets per time step,
> whilst still scheduling an integer (by necessity) number of dicrete
> packets per timestep in some reasonable fashion ?
>
> I have thought about defining say, 100 basic Swarm time steps to
> represent 1 simulated time unit, and thus obtaining fractional values
> which resolve to 1/100 of a simulated time unit, but some kind of binning
> would still be required and I wonder if anybody knows of a better
> system....
>
>
> thanks,
> Andre Costa


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