/// <summary>
/// Sample code simulating a news recommendation scenario. In this simple example,
/// the rendering server has to pick 1 out of 4 news topics to show to users (e.g. as featured article).
/// </summary>
/// <remarks>
/// NOTE: For this sample to work, the proper settings must be set at deployment time:
/// Vowpal Wabbit Switches = --cb_explore_adf --epsilon 0.2 --cb_type dr
/// </remarks>
public static async Task NewsRecommendation()
{
if (String.IsNullOrWhiteSpace(SettingsBlobUri))
{
Console.WriteLine("Please specify a valid settings URL.");
return;
}
// Create configuration for the decision service
var serviceConfig = new DecisionServiceConfiguration(settingsBlobUri: SettingsBlobUri);
// Enable development mode to easily debug / diagnose data flow and system properties
// This should be turned off in production deployment
serviceConfig.DevelopmentMode = true;
using (var service = DecisionService.Create <UserContextADF>(serviceConfig))
{
var random = new Random();
int user = 0; // user id
int maxDecisionHistory = 100; // max number of past decisions to record
var correctDecisions = new Queue <int>(); // keeps track of past decisions
Console.WriteLine("Press Ctrl + C at any time to cancel the process.");
// Each topic has its own set of features
var topicFeatures = Enumerable.Range(1, 10)
.Select(_ => new TopicFeature
{
Features = Enumerable.Range(1, 10).Select(f => (float)random.NextDouble()).ToArray()
})
.ToArray();
while (true)
{
user++;
string uniqueKey = Guid.NewGuid().ToString();
var userContext = new UserContextADF
{
Gender = random.NextDouble() > 0.5 ? "male" : "female",
TopicFeatures = topicFeatures.Take(random.Next(5, topicFeatures.Length)).ToArray()
};
int[] topicRanking = await service.ChooseRankingAsync(uniqueKey, userContext);
int topicId = topicRanking[0];
// Display the news topic chosen by exploration process.
Console.WriteLine("Topic {0} was chosen for user {1}.", topicId, user + 1);
// Report {0,1} reward as a simple float.
// In a real scenario, one could associated a reward of 1 if user
// clicks on the article and 0 otherwise.
float reward = 0;
if (userContext.Gender == "male" && topicId == 3)
{
reward = 1;
}
else if (userContext.Gender == "female" && topicId == 8)
{
reward = 1;
}
service.ReportReward(reward, uniqueKey);
correctDecisions.Enqueue((int)reward);
if (correctDecisions.Count == maxDecisionHistory)
{
correctDecisions.Dequeue();
}
if (user % 50 == 0)
{
Console.WriteLine("Correct decisions out of last {0} interactions: {1}", maxDecisionHistory, correctDecisions.Sum());
}
System.Threading.Thread.Sleep(TimeSpan.FromMilliseconds(50));
}
}
}
public static IReadOnlyCollection <TopicFeature> GetFeaturesFromContext(UserContextADF context)
{
return(context.TopicFeatures);
}
