small_world_iterator& operator++()
{
target = (target + 1) % n;
if (target == (source + k/2 + 1) % n) {
++source;
if (allow_self_loops) target = source;
else target = (source + 1) % n;
}
current.first = source;
uniform_01<RandomGenerator, double> rand01(*gen);
uniform_int<vertices_size_type> rand_vertex_gen(0, n-1);
double x = rand01();
*gen = rand01.base(); // GRRRR
if (x < prob) {
vertices_size_type lower = (source + n - k/2) % n;
vertices_size_type upper = (source + k/2) % n;
do {
current.second = rand_vertex_gen(*gen);
} while ((current.second >= lower && current.second <= upper)
|| (upper < lower
&& (current.second >= lower || current.second <= upper)));
} else {
current.second = target;
}
return *this;
}
small_world_iterator(RandomGenerator& gen, vertices_size_type n,
vertices_size_type k, double prob = 0.0,
bool allow_self_loops = false, bool allow_multiple_edges = true)
: gen(&gen), n(n), k(k+k%2), prob(prob), source(0),
target(allow_self_loops? 0 : 1),
allow_self_loops(allow_self_loops),
allow_multiple_edges(allow_multiple_edges),
current(0, allow_self_loops? 0 : 1),
#if !defined BOOST_NO_HASH
edges(allow_multiple_edges? 0 : (k + k%2)*n/2)
#else
edges()
#endif
{}
reference operator*() const { return current; }
pointer operator->() const { return ¤t; }
small_world_iterator& operator++()
{
current.first = source;
uniform_01<RandomGenerator, double> rand01(*gen);
uniform_int<vertices_size_type> rand_vertex_gen(0, n-1);
double x = rand01();
*gen = rand01.base(); // GRRRR
vertices_size_type larger_v = 0;
vertices_size_type smaller_v = 0;
if (x < prob) {
do {
current.second = rand_vertex_gen(*gen);
if (!allow_multiple_edges) {
larger_v = current.first;
smaller_v = current.second;
if (current.first < current.second) {
smaller_v = current.first;
larger_v = current.second;
}
}
// std::cout << "swg " << current.first << " " << current.second << " " << smaller_v*n + larger_v << std::endl;
} while ((!allow_self_loops && current.first == current.second)
||
(!allow_multiple_edges && (current.first < k/2 && current.second >= n - k/2 + current.first))
||
(!allow_multiple_edges && (edges.find(smaller_v*n + larger_v) != edges.end())));
} else {
current.second = target;
if (!allow_multiple_edges) {
larger_v = current.first;
smaller_v = current.second;
if (current.first < current.second) {
smaller_v = current.first;
larger_v = current.second;
}
}
}
if (!allow_multiple_edges) {
edges.insert(smaller_v*n + larger_v);
// std::cout << "added " << current.first << " " << current.second << " " << smaller_v*n + larger_v << std::endl;
}
target = (target + 1) % n;
if (target == (source + k/2 + 1) % n) {
++source;
if (allow_self_loops) target = source;
else target = (source + 1) % n;
}
return *this;
}
small_world_iterator operator++(int)
{
small_world_iterator temp(*this);
++(*this);
return temp;
}
