If you want to imitate electrical charges, the charge is a property of the particle, not the "link". The electrostatic force between two is given by the product of the two charges divided by the square of the distance between them. Your link construct is good for keeping track of the distances.

A real physical model would need to keep track of magnetic effects and radiation, too. For that, a construct called the vector potential will be useful.

You may also be missing the dynamical aspect of the problem. The inertia of the particles determines their response to a force (F=ma and its relativistic descendant).

An elementary physics text will explain how to use that, with examples and exercises.

After Compline,
Zaxo

Not to sound harsh, but since you pointed out to the one reply that offered actual Perl that "I know perl. I'm already past that stage", how is this a Perl programming issue? It seems more like a particle physics or electron dynamics problem. You might be better-suited to asking for help in those types of forums, and come to this forum when you need help on things more specific to Perl.

--rjray

Greetings again,
I have asked this question wrong - and indeed, was somewhat harsh to the first reply.
You are quite right - this is, technically, not a perl question per se - but since this code will be implemented in perl, I hoped it would be close enough that I would be able to arouse the brains of others into helping me with this conundrum

I felt that the question posed showed enough complexity that a very simple "How to use foreach" was clearly not what I wanted in an answer thus the short, sharp nature of my reply.
HOWEVER in saying that, the fact that jhanna gave me an explanation that quite possibly a number of monks would say 'What a moron, go read a book' is a good thing.
So, thanks jhanna, my apologies for being short - but that wasn't quite the answer I was looking for.

I'm going to restate my question like I should have in the first place. The possibly misleading manner I asked it in was how the simulation was explained to me:
I was playing around with making my own IP map. Nothing large, just my local network for a laugh and to show off. The nodes are the IP addresses, the links are the routes between them.
You do multiple traceroutes, from multiple locations to create an interlinked "map" (Which I have neatly stored in a MySQL DB). The "distance" between nodes is calculated from the average "distance", in milliseconds, from IP addresses in the traceroute.
The links are like springs, their repulsion charge is the given distance, and when set going in the simulation, the nodes will push each other apart in such a way that they place themselves roughly in space to equate the "distances" from other IP addresses...
I want all the co-ordinates, after the simulation has run and spaced them accordingly, to dump into POVray.

I hope this is more clear,
JP,
-- Alexander Widdlemouse undid his bellybutton and his bum dropped off --

Well, I'm no theoretical mathematician, but I think your problem is going to involve compromise on some level. In fact, for even three nodes, it's possible that the "link distance" is insolvable, if the ping times between A and B exceed the sum of the ping times from A to C and C to B. So whatever algorithm you choose, it's going to involve some sort of first order approximation, and a satisfaction threshold, rather than some rigid math. Maybe that will help decide how to do it.

-- Randal L. Schwartz, Perl hacker

Randomly (or equally for that matter) place them on the surface of a very very large sphere. The force between particles is the distance minus the ping. Scale it by a factor of 100 or so (mass of particle). That will be your acceleration (distance and acceleration are vectors remember) for that link. Calculate one for each link the particle has. Store the acceleration per link for later. Go to the next particle and repeat. Note acceleration(a->b) == -acceleration(b->a) if all particles have equal mass. Once you have all of the acceleration vectors for each particle-particle link visit each particle, sum it's acceleration vector (should point roughly towards 0,0,0) and move the particle acceleration times time (assume 1). Repeat. You will have to tune it a bit, what to use for mass, how far apart to start, maybe modify the acceleration calculation to push out harder when particles are too close than it would pull when the particles were too far apart. Over time/iterations it just might converge ;). The usual method would be to stop when the accelerations are all under a certain amount (should approach zero).

for $node (@nodes) {
 for $link ($node->{links}) {
  &updatePosition($link->node,$link);
 }
}
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Put two like charges in deep space and the distance between them will become very large.

Update: Since it's a non-Perl question anyway, here's the C++ subroutines for the important bit.

// double position[12][3] and double velocity[12][3] are global 
//  arrays of 3D vectors
// int edge[0] and int edge[1] are the indices in position[][3] and
//  velocity[][3] of the two nodes making up this edge, or link

// double friction is about 0.9999
// double natural is about 1 

void icosahedron::cord(const int *edge) {
    double s[3], rr;
    rr=0;
    for (int i=0; i<3; i++) {
        s[i]=position[edge[1]][i]-position[edge[0]][i];
        rr+=s[i]*s[i];
    }
    if (rr>0) {
        double strain=spring*(natural/sqrt(rr)-1);
        for (int i=0; i<3; i++) {
            rr=strain*s[i];
            velocity[edge[0]][i]-=rr;
            velocity[edge[1]][i]+=rr;
        }
    }
}
//-------------------------------------------------
void icosahedron::move() {
    double *pos,*vel;
    for (pos=*position, vel=*velocity; pos-*position<36; pos++, vel++)
        *pos+=*vel;
    for (vel=*velocity; vel-*velocity<36; vel+=3) 
        *vel*=friction;
}
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