Exemple #1
0
		private static int[] Calculeaza_vecini_LSH(int k, int id_user)
        {
            // Extragem din DB un Dictionary de toate id utilizator, lista de preparate
            // comandate.
            Dictionary<int, List<int>> toatePrep = DatabaseFunctions.
                preparateComandateDupaUtilizator();
            Dictionary<int, HashSet<int>> signatures = new Dictionary<int, HashSet<int>>();
            HashSet<int> single_signatures = new HashSet<int>();

            foreach (KeyValuePair<int, List<int>> entry in toatePrep)
            {
                signatures.Add(entry.Key, entry.Value.ToHashSet<int>());
                single_signatures.UnionWith(entry.Value);
            }

            int numSets = signatures.Count;
            int numHashFunctions = single_signatures.Count;

            MinHash<int> minHash = new MinHash<int>(numHashFunctions);
            int[][] minHashValues = minHash.initializeHashBuckets(numSets,
                numHashFunctions);

            int index = 0, index_cautat = 0;
            List<HashSet<int>> list_signatures = new List<HashSet<int>>();
            foreach(var entry in signatures)
            {
                minHash.computeMinHashForSet(entry.Value, index, minHashValues,
                    single_signatures);
                if(entry.Key == id_user)
                {
                    index_cautat = index;
                }
                index++;
                list_signatures.Add(entry.Value);
            }

            

            LSH<int> lsh = new LSH<int>(minHashValues, list_signatures);
            Dictionary<int, double> closeSimilarItems = lsh.closestSimilarItems(index_cautat, minHash);

            int poz = 0;
            int[] vecini = new int[k];
            Dictionary<int, double> results = new Dictionary<int,double>();
            int i = 0;

            foreach(var closeItem in closeSimilarItems)
            {
                poz = closeItem.Key;
                i = 0;
                foreach (var entry in signatures)
                {
                    if (i == poz)
                    {
                        results.Add(entry.Key, closeItem.Value);
                        break;
                    }
                    i++;

                }

            }
            if (results.Count() > 0)
            {
                for (int ind = 0; ind < k; ind++)
                {
                    vecini[ind] = results.MaxBy(x => x.Value).Key;
                    results.Remove(vecini[ind]);
                    if (results.Count == 0) break;
                }
            }

            return vecini;

        }