# Does anyone else get email requests from strangers?

Mon, 6 May 96 10:18:00 PDT

This is bizarre.
1. This person has a PhD, why can't he figure it out himself?
2. He's offered me no monetary compensation whatsoever.
Does he think my time is worth nothing?
3. He gives me no reason why he's ASKING ME to do his work
for him. Hello? Why not ask someone in his organization?

Sometimes I hate the Internet for the very reason that it now
gives complete strangers a medium through which to waste my time.
I used to leave that job for my friends....

> From ao718@rgfn.epcc.edu Sun May 5 14:22:03 1996
>
> Dear Mr. Rifkin,
>
> I was working as a Senior Scientific Officer at Thin Film Laboratory,
> Physics Department, IIT(Indian Institute of Technology)-Delhi after
> obtaining Ph.D from the same Institute. I came to USA to present two
> Research papers in an International Conference on Thin Films and
> Metallurgical Coatings which was held at San Diego, CA, last year.
> Presently I am learning computer programming particularly I am
> interested in Data Communication. I am facing problem with one algorithm
> which is meant to find the shortest path in computer network and packet
> switching. I am basically from physics background, hence NOT a expert in
> Algorithms. I would appreciate if you kindly help me to write the
> algorithm in Bellman-Ford form.
>
> Problem is this:
>
> s = source node
> N = set of nodes in the network
> M = set of nodes so far incorporated in the algorithm
> dij = link cost from node i to nodej
> Dn = cost of the least-cost path from node s to node n that is currently
> known to the algorithm
>
> Dijkstra's algorithm can be expressed in the following program:
>
> for n: = 1 to N do
> begin
> D[n]: = infinity(symbol); final[n]: = false;{all nodes are
> temporarily labeled with infinity}
>
> pred[n]: = -1
> end;
> D[s]: = 0; final[s]: = true; {node s is permanently labeled with 0}
> recent: = s;
> path: = true;
> {initialization over}
>
> 1 for n: = 1 to N do {find new label}
> if (d[recent, n] < infinity) AND (NOT final[n]) then
> {for every immediate successor of recent that is not permanently
> labeled, do}
> begin{update temporary labels}
> newlabel: = D[recent] + d[recent,n];
> if newlabel < D[n] then
> begin D[n]: = newlabel; pred[n]: recent end
> {relabel n if there is a shorter path via node
> recent and make
> recent the predecessor of n on the shortest path
> from s}
> end;
> temp: = infinity;
> for d: = 1 to N do { find node with smallest
> temporary label}
> if (NOT final[x] AND (D[x] < temp) then
> begin y: = x; temp: D[x] emd;
> if temp<infinity then { there is a path}
>
> begin final[y]: = true; recent:=y end
> {y, the next closest node to s gets permanently labeled}
>
> In this program, each node is assigned a temporarly label initially. As a
> final path to a node is determined, it is assigned a permanent label
> equal to the cost of the path from s.
>
> Please WRITE a similar program for the Bellman-Ford algorithm. Hint: The
> Bellman-Ford algorithm is often called a label-correcting method, in
> contrast to Dijkstra's label-setting method.
>
> THE ABOVE PROBLEM IS GIVEN IN PAGE 338, OF WILLIAM STALLINGS, 4TH
> EDITION.
>