routing_distance.m

best routing protocol

function [pair_dist, pair_hops]=routing_distance(neighbor_dist, ...
		 routing_nexthop, test_pairs)
%neighbor_dist(i,j): distance between i & j if they are neighbor,
%or infinity
%routing_nexthop(i,j): the next hop from i when routing from i to j
%pair_dist(i,j): distance using the routing_nexthop
%pair_hops(i,j): how many hops it takes to route from i to j
N = length(neighbor_dist);

if nargin<3
  p = 0; % test all pairs
  pair_hops = zeros(N,N);
  pair_dist = zeros(N,N);
  fromloop = 1:N;
else
  [p, tmp] = size(test_pairs);
  pair_hops = zeros(p,1);
  pair_dist = zeros(p,1);
  fromloop = test_pairs(:,1)';
end
count = 0;
for from=fromloop
  if p==0
    toloop = 1:N;
  else
    toloop = test_pairs(count+1,2);
  end
  
  for to=toloop
    %current_nodes = [];
    count = count +1;
    n_hops = 0;
    next = from;
    tmp = 0;
    seen_nodes = zeros(N,1);
    while next~=to 
      previous = next;
      next = routing_nexthop(next, to);
      %if sum(ismember(current_nodes, next))>0
      if next<0
	%fprintf('DEAD loop\n');
	%print_route(routing_nexthop, from, to);
	tmp = Inf;
	n_hops=Inf;
	break
      end
      if seen_nodes(next)
	%fprintf('DEAD loop\n');
	%print_route(routing_nexthop, from, to);
	tmp = Inf;
	n_hops=Inf;
	break
      end
      n_hops = n_hops + 1;
      %current_nodes(n_hops) = next;
      seen_nodes(next) = 1;
      tmp = tmp + neighbor_dist(previous, next);
    end
    
    pair_dist(count)=tmp;
    pair_hops(count)=n_hops;
    
  end
end