public IDMultisetItemList PotentialFriendsPLinq(SubscriberID id, int maxCandidates)
{
var candidates =
subscribers[id].Friends.AsParallel() // Map
.SelectMany(friend => subscribers[friend].Friends)
.Where(foaf => foaf != id && !(subscribers[id].Friends.Contains(foaf))) // remove self, own friends
.GroupBy(foaf => foaf) // Reduce
.Select(foafGroup => new IDMultisetItem(foafGroup.Key, foafGroup.Count()));
return(Multiset.MostNumerous(candidates, maxCandidates)); // postprocess results of Reduce
}
public IDMultisetItemList PotentialFriendsParallel(SubscriberID id, int maxCandidates)
{
object locker = new object();
IDMultiset candidates = new IDMultiset();
Parallel.ForEach(subscribers[id].Friends, // Map over friends
() => Multiset.Create(new HashSet <SubscriberID>()), // init thread-local state localFoafs with empty Multiset
(friend, loopState, localFoafs) =>
{
var foafs = subscribers[friend].FriendsCopy();
foafs.RemoveWhere(foaf => foaf == id || subscribers[id].Friends.Contains(foaf)); // remove self, own friends
return(Multiset.Union(localFoafs, Multiset.Create(foafs))); // Reduce, thread-local
},
localFoafs => { lock (locker) candidates = Multiset.Union(localFoafs, candidates); }); // Reduce, among threads
return(Multiset.MostNumerous(candidates, maxCandidates)); // postprocess results of Reduce
}
public IDMultisetItemList PotentialFriendsSequential(SubscriberID id, int maxCandidates)
{
// Map
var foafsList = new List <IDMultiset>();
foreach (SubscriberID friend in subscribers[id].Friends)
{
var foafs = subscribers[friend].FriendsCopy();
foafs.RemoveWhere(foaf => foaf == id || subscribers[id].Friends.Contains(foaf)); // remove self, own friends
foafsList.Add(Multiset.Create(foafs));
}
// Reduce
IDMultiset candidates = new IDMultiset();
foreach (IDMultiset foafs in foafsList)
{
candidates = Multiset.Union(foafs, candidates);
}
// Postprocess
return(Multiset.MostNumerous(candidates, maxCandidates));
}
/// <summary>
/// Usage: SocialNework subscriberCount maxFriends
/// Both arguments are optional, defaults are 1000 and 10.
/// </summary>
static void Main(string[] args)
{
Console.WriteLine("Social Network Sample\n");
#if DEBUG
Console.WriteLine("For most accurate timing results, use Release build.\n");
#endif
Random random = new Random(1); // seed for random but reproducible runs
// Defaults for data generation, may override some on command line
int subscriberCount = 10000;
int maxFriends = 2000;
// Defaults for printed table of results
const int maxRows = 16;
const int maxCols = 8;
const int maxCandidates = maxRows;
// Optionally override some defaults on command line
if (args.Length > 0)
{
subscriberCount = Int32.Parse(args[0], CultureInfo.CurrentCulture);
}
if (args.Length > 1)
{
maxFriends = Int32.Parse(args[1], CultureInfo.CurrentCulture);
}
Console.WriteLine("Creating data...");
// Allocate subscribers, assign friends for timing tests
SubscriberRepository subscribers = new SubscriberRepository(subscriberCount);
subscribers.AssignRandomFriends(maxFriends, random);
// Print a few subscribers and a summary
Console.WriteLine();
Console.WriteLine("Some subscribers and some of their friends");
subscribers.Print(maxRows, maxCols);
Console.WriteLine();
Console.WriteLine("{0} subscribers in all, with up to {1} friends or even more ", subscriberCount, maxFriends);
// Choose a subscriber seeking friends
const SubscriberID id = 0;
var subscriber = subscribers.GetSubscriber(id);
Console.WriteLine();
Console.WriteLine("Find potential friends for this subscriber, with these friends:");
Console.Write("{0,10:D}", id);
subscriber.Print(subscriber.Friends.Count);
Console.WriteLine();
// Sequential for
var candidates = new IDMultisetItemList(); // to sort, must use list of Multiset items not Multiset itself
SampleUtilities.TimedRun(() =>
{
candidates = subscribers.PotentialFriendsSequential(id, maxCandidates);
return(candidates.Count);
},
" Sequential for");
Console.WriteLine();
int rows = Math.Min(maxRows, candidates.Count);
Console.WriteLine("{0} potential friends for this subscriber, and the number of mutual friends", rows);
Multiset.Print(candidates);
Console.WriteLine();
// Parallel.ForEach
SampleUtilities.TimedRun(() =>
{
candidates = subscribers.PotentialFriendsParallel(id, maxCandidates);
return(candidates.Count);
},
"Parallel.ForEach");
Console.WriteLine();
rows = Math.Min(maxRows, candidates.Count);
Console.WriteLine("{0} potential friends for this subscriber, and the number of mutual friends", rows);
Multiset.Print(candidates);
Console.WriteLine();
// Sequential LINQ
SampleUtilities.TimedRun(() =>
{
candidates = subscribers.PotentialFriendsLinq(id, maxCandidates);
return(candidates.Count);
},
" Sequential LINQ");
Console.WriteLine();
rows = Math.Min(maxRows, candidates.Count);
Console.WriteLine("{0} potential friends for this subscriber, and the number of mutual friends", rows);
Multiset.Print(candidates);
Console.WriteLine();
// PLINQ
SampleUtilities.TimedRun(() =>
{
candidates = subscribers.PotentialFriendsPLinq(id, maxCandidates);
return(candidates.Count);
},
" PLINQ");
Console.WriteLine();
rows = Math.Min(maxRows, candidates.Count);
Console.WriteLine("{0} potential friends for this subscriber, and the number of mutual friends", rows);
Multiset.Print(candidates);
Console.WriteLine("\nRun complete... press enter to finish.");
Console.ReadLine();
}