public TResult RecommendItem <TResult>(string itemId, IResultBuilderFactory <TResult> resultBuilderFactory)
{
if (itemId == null)
{
throw new ArgumentNullException(nameof(itemId));
}
if (!this.itemMap.ContainsKey(itemId))
{
return(resultBuilderFactory.CreateEmpty());
}
var yi = this.itemFactors.Row(this.itemMap[itemId]);
var yj = Vector <double> .Build.Dense(this.factors);
var resultBuilder = resultBuilderFactory.CreateBuilder(maximumCapacity: this.itemMap.Count);
foreach (var item in this.itemMap)
{
var j = item.Value;
this.itemFactors.Row(j, yj);
resultBuilder.Append(item.Key, yi.DotProduct(yj) / this.ItemNorms[j]);
}
return(resultBuilder.ToResult());
}
public TResult RankUsers <TResult>(UserFeatures user, List <KeyValuePair <string, UserFeatures> > users, IResultBuilderFactory <TResult> resultBuilderFactory)
{
if (user == null)
{
throw new ArgumentNullException(nameof(user));
}
if (users == null)
{
throw new ArgumentNullException(nameof(users));
}
var xu = user.Vector;
var resultBuilder = resultBuilderFactory.CreateBuilder(maximumCapacity: users.Count);
foreach (var pair in users)
{
var xv = pair.Value.Vector;
var norm = pair.Value.Norm;
var score = xu.DotProduct(xv) / norm;
resultBuilder.Append(pair.Key, score);
}
return(resultBuilder.ToResult());
}
public TResult RecommendUser <TResult>(UserFeatures user, IResultBuilderFactory <TResult> resultBuilderFactory)
{
if (user == null)
{
throw new ArgumentNullException(nameof(user));
}
var xu = user.Vector;
var yi = Vector <double> .Build.Dense(this.factors);
var resultBuilder = resultBuilderFactory.CreateBuilder(maximumCapacity: this.itemMap.Count);
foreach (var item in this.itemMap)
{
this.itemFactors.Row(item.Value, yi);
resultBuilder.Append(item.Key, xu.DotProduct(yi));
}
return(resultBuilder.ToResult());
}