diff --git a/.travis.yml b/.travis.yml
index ec490b6..d75cf7d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -20,7 +20,10 @@ before_install:
 - |
   if [ "$TRAVIS_OS_NAME" = "linux" ]; then export CXX=g++-4.8 CC=gcc-4.8; fi
   if [ "$TRAVIS_OS_NAME" = "osx" ] && [ "${PYTHON:0:1}" = "3" ]; then
-      brew update; brew install python3; rvm get head || true 
+      brew update
+      brew install python3
+      command curl -sSL https://rvm.io/mpapis.asc | gpg --import -;
+      rvm get stable
   fi
   pip install --user --upgrade pip virtualenv
   virtualenv -p python$PYTHON venv
diff --git a/similarity_search/include/method/falconn.h b/similarity_search/include/method/falconn.h
index d600e98..0b90efd 100644
--- a/similarity_search/include/method/falconn.h
+++ b/similarity_search/include/method/falconn.h
@@ -84,7 +84,6 @@ class FALCONN : public Index<dist_t> {
   // createDenseDataPoint assumes that p was initialized using dim_ as the number of elements.
   void createDenseDataPoint(const Object* o, DenseFalconnPoint& p, bool normData) const;
 
-  const ObjectVector&     data_;
   Space<dist_t>&          space_;
   bool                    sparse_;
   size_t                  dim_; // only for dense vector spaces
diff --git a/similarity_search/include/method/lsh.h b/similarity_search/include/method/lsh.h
index 34d74ba..feb7254 100644
--- a/similarity_search/include/method/lsh.h
+++ b/similarity_search/include/method/lsh.h
@@ -143,7 +143,6 @@ class LSH : public Index<dist_t> {
  private:
   typedef lshkit::LshIndex<TailRepeatHash<lsh_t>, unsigned> LshIndexType;
 
-  const ObjectVector& data_;
   int p_;
   lshkit::FloatMatrix* matrix_;
   LshIndexType* index_;
diff --git a/similarity_search/include/method/lsh_multiprobe.h b/similarity_search/include/method/lsh_multiprobe.h
index 8531542..edbe0ae 100644
--- a/similarity_search/include/method/lsh_multiprobe.h
+++ b/similarity_search/include/method/lsh_multiprobe.h
@@ -52,7 +52,6 @@ class MultiProbeLSH : public Index<dist_t> {
  private:
   typedef lshkit::MultiProbeLshIndex<unsigned> LshIndexType;
 
-  const ObjectVector& data_;
   int dim_;
   lshkit::FloatMatrix* matrix_;
   LshIndexType* index_;
diff --git a/similarity_search/include/method/nndes.h b/similarity_search/include/method/nndes.h
index 385c09b..8dedbba 100644
--- a/similarity_search/include/method/nndes.h
+++ b/similarity_search/include/method/nndes.h
@@ -86,7 +86,6 @@ class NNDescentMethod : public Index<dist_t> {
 
 
   const Space<dist_t>&    space_;
-  const ObjectVector&     data_;
   bool                    PrintProgress_;
 
   size_t                  NN_; // K in the original Wei Dong's code nndes.cpp
diff --git a/similarity_search/src/method/falconn.cc b/similarity_search/src/method/falconn.cc
index 5639a3d..50882e0 100644
--- a/similarity_search/src/method/falconn.cc
+++ b/similarity_search/src/method/falconn.cc
@@ -107,7 +107,7 @@ void FALCONN<dist_t>::copyData(bool normData, bool centerData, size_t max_sparse
   SpaceSparseVectorInter<dist_t>* pSparseSpace = dynamic_cast<SpaceSparseVectorInter<dist_t>*>(&space_);
   VectorSpace<dist_t>*            pDenseSpace  = dynamic_cast<VectorSpace<dist_t>*>(&space_);
 
-  if (data_.empty()) return;
+  if (this->data_.empty()) return;
   if (pSparseSpace == nullptr && pDenseSpace == nullptr) {
     throw runtime_error("Only dense vector spaces and FAST sparse vector spaces are supported!");
   }
@@ -116,7 +116,7 @@ void FALCONN<dist_t>::copyData(bool normData, bool centerData, size_t max_sparse
     sparse_ = true;
     SparseFalconnPoint p;
     dim_ = 0;
-    for (const Object* o: data_) {
+    for (const Object* o: this->data_) {
       createSparseDataPoint(o, p, normData);
       falconn_data_sparse_.push_back(p);
       if (p.size())
@@ -137,9 +137,9 @@ void FALCONN<dist_t>::copyData(bool normData, bool centerData, size_t max_sparse
   }
   if (pDenseSpace != nullptr) {
     LOG(LIB_INFO) << "Copying a dense vector data set.";
-    dim_ = data_[0]->datalength() / sizeof(dist_t);
+    dim_ = this->data_[0]->datalength() / sizeof(dist_t);
     DenseFalconnPoint p(dim_);
-    for (const Object* o: data_) {
+    for (const Object* o: this->data_) {
       createDenseDataPoint(o, p, normData);
       falconn_data_dense_.emplace_back(p);
     }
@@ -171,7 +171,7 @@ void FALCONN<dist_t>::copyData(bool normData, bool centerData, size_t max_sparse
 
 template <typename dist_t>
 FALCONN<dist_t>::FALCONN(Space<dist_t>& space,
-                         const ObjectVector& data) : data_(data), space_(space), sparse_(false),
+                         const ObjectVector& data) : Index<dist_t>(data), space_(space), sparse_(false),
                                                      dim_(0), num_probes_(10) {
 }
 
@@ -242,7 +242,7 @@ void FALCONN<dist_t>::CreateIndex(const AnyParams& IndexParams)  {
    * The current formula mimics the Glove setup in ann_benchmarks,
    * where a roughly 2^20 entry data sets uses 16-bit tables.
    */
-  size_t num_hash_bits = max<size_t>(2, static_cast<size_t>(floor(log2(data_.size()>>4))));
+  size_t num_hash_bits = max<size_t>(2, static_cast<size_t>(floor(log2(this->data_.size()>>4))));
   pmgr.GetParamOptional(PARAM_NUM_HASH_BITS, num_hash_bits, num_hash_bits);
 
   /*
@@ -312,17 +312,17 @@ void FALCONN<dist_t>::Search(KNNQuery<dist_t>* query, IdType) const {
     }
     // Recomputing distances for k nearest neighbors should have a very small impact on overall performance
     for (IdType ii : ids) {
-      query->CheckAndAddToResult(data_[ii]);
+      query->CheckAndAddToResult(this->data_[ii]);
     }
   } else {
     if (sparse_) {
       SparseFalconnPoint sparseQ;
       createSparseDataPoint(query->QueryObject(), sparseQ, norm_data_);
-      falconn_table_sparse_->find_k_nearest_neighbors(sparseQ, center_point_.get(), query, &data_, query->GetK(), &ids);
+      falconn_table_sparse_->find_k_nearest_neighbors(sparseQ, center_point_.get(), query, &this->data_, query->GetK(), &ids);
     } else {
       DenseFalconnPoint denseQ(dim_);
       createDenseDataPoint(query->QueryObject(), denseQ, norm_data_);
-      falconn_table_dense_->find_k_nearest_neighbors(denseQ, center_point_.get(), query, &data_, query->GetK(), &ids);
+      falconn_table_dense_->find_k_nearest_neighbors(denseQ, center_point_.get(), query, &this->data_, query->GetK(), &ids);
     }
   }
 }
diff --git a/similarity_search/src/method/lsh.cc b/similarity_search/src/method/lsh.cc
index 8b0e2d4..0f657f5 100644
--- a/similarity_search/src/method/lsh.cc
+++ b/similarity_search/src/method/lsh.cc
@@ -27,7 +27,7 @@ namespace similarity {
 template <typename dist_t, typename lsh_t, typename paramcreator_t>
 LSH<dist_t, lsh_t, paramcreator_t>::LSH(const Space<dist_t>& space,
                                         const ObjectVector& data,
-                                        int P) : data_(data), p_(P) {
+                                        int P) : Index<dist_t>(data), p_(P) {
 
 }
 
@@ -43,15 +43,15 @@ void LSH<dist_t, lsh_t, paramcreator_t>::CreateIndex(const AnyParams& IndexParam
   pmgr.GetParamOptional("W",  LSH_W, 20);
   pmgr.GetParamOptional("M",  LSH_M, 20);
   pmgr.GetParamOptional("L",  LSH_L, 50);
-  pmgr.GetParamOptional("H",  LSH_H, data_.size() + 1);
+  pmgr.GetParamOptional("H",  LSH_H, this->data_.size() + 1);
 
   int is_float = std::is_same<float,dist_t>::value;
   CHECK_MSG(is_float, "LSH works only for single-precision numbers");
   CHECK_MSG(sizeof(dist_t) == sizeof(float), "LSH works only for single-precision numbers");
-  CHECK_MSG(!data_.empty(), "The data set shouldn't be empty");
+  CHECK_MSG(!this->data_.empty(), "The data set shouldn't be empty");
   CHECK_MSG(p_ == 1 || p_ == 2, "The value of the space selector should be either 1 or 2!");
 
-  const size_t datalength = data_[0]->datalength();
+  const size_t datalength = this->data_[0]->datalength();
 
   LOG(LIB_INFO) << "W (window size (used only for LSHCauchy and LSHGaussian)) : "  << LSH_W;
   LOG(LIB_INFO) << "M (# of hash functions) : "  << LSH_M;
@@ -59,11 +59,11 @@ void LSH<dist_t, lsh_t, paramcreator_t>::CreateIndex(const AnyParams& IndexParam
   LOG(LIB_INFO) << "H (# hash table size) :   "  << LSH_H;
 
   const int dim = static_cast<int>(datalength / sizeof(float));
-  matrix_ = new lshkit::FloatMatrix(dim, static_cast<int>(data_.size()));
+  matrix_ = new lshkit::FloatMatrix(dim, static_cast<int>(this->data_.size()));
 
-  for (size_t i = 0; i < data_.size(); ++i) {
-    CHECK(datalength == data_[i]->datalength());
-    const float* x = reinterpret_cast<const float*>(data_[i]->data());
+  for (size_t i = 0; i < this->data_.size(); ++i) {
+    CHECK(datalength == this->data_[i]->datalength());
+    const float* x = reinterpret_cast<const float*>(this->data_[i]->data());
     for (int j = 0; j < dim; ++j) {
       (*matrix_)[i][j] = x[j];
     }
@@ -115,7 +115,7 @@ void LSH<dist_t, lsh_t, paramcreator_t>::Search(KNNQuery<dist_t>* query, IdType)
   const lshkit::Topk<uint32_t>& knn = query_scanner.topk();
   for (size_t i = 0; i < knn.size(); ++i) {
     if (knn[i].key != std::numeric_limits<uint32_t>::max()) {
-      query->CheckAndAddToResult(knn[i].dist, data_[knn[i].key]);
+      query->CheckAndAddToResult(knn[i].dist, this->data_[knn[i].key]);
     }
   }
 }
diff --git a/similarity_search/src/method/lsh_multiprobe.cc b/similarity_search/src/method/lsh_multiprobe.cc
index 711b54d..8ef468b 100644
--- a/similarity_search/src/method/lsh_multiprobe.cc
+++ b/similarity_search/src/method/lsh_multiprobe.cc
@@ -26,7 +26,7 @@ namespace similarity {
 
 template <typename dist_t>
 MultiProbeLSH<dist_t>::MultiProbeLSH(const Space<dist_t>& space,
-                                     const ObjectVector& data) : data_(data) {
+                                     const ObjectVector& data) : Index<dist_t>(data) {
 }
 
 template <typename dist_t>
@@ -43,7 +43,7 @@ void MultiProbeLSH<dist_t>::CreateIndex(const AnyParams& IndexParams) {
 
     pmgr.GetParamOptional("M",  LSH_M,  20);
     pmgr.GetParamOptional("L",  LSH_L,  50);
-    pmgr.GetParamOptional("H",  LSH_H,  data_.size() + 1);
+    pmgr.GetParamOptional("H",  LSH_H,  this->data_.size() + 1);
     pmgr.GetParamOptional("W",  LSH_W,  20);
     pmgr.GetParamOptional("T",  LSH_T,  10);
     pmgr.GetParamOptional("tuneK",  LSH_TuneK, 1);
@@ -52,7 +52,7 @@ void MultiProbeLSH<dist_t>::CreateIndex(const AnyParams& IndexParams) {
 
     // For FitData():
     // number of points to use
-    unsigned N1 = data_.size();
+    unsigned N1 = this->data_.size();
     // number of pairs to sample
     unsigned P = 10000;
     // number of queries to sample
@@ -82,7 +82,7 @@ void MultiProbeLSH<dist_t>::CreateIndex(const AnyParams& IndexParams) {
     unsigned F = 10;
     // For MPLSHTune():
     // dataset size
-    unsigned N2 = data_.size();
+    unsigned N2 = this->data_.size();
     // desired recall
 
     CreateIndexInternal(
@@ -113,13 +113,13 @@ void MultiProbeLSH<dist_t>::CreateIndexInternal(
   int is_float = std::is_same<float,dist_t>::value;
   CHECK(is_float);
   CHECK(sizeof(dist_t) == sizeof(float));
-  CHECK(!data_.empty());
-  const size_t datalength = data_[0]->datalength();
+  CHECK(!this->data_.empty());
+  const size_t datalength = this->data_[0]->datalength();
   dim_ = static_cast<int>(datalength / sizeof(float));
-  matrix_ = new lshkit::FloatMatrix(dim_, static_cast<int>(data_.size()));
-  for (size_t i = 0; i < data_.size(); ++i) {
-    CHECK(datalength == data_[i]->datalength());
-    const float* x = reinterpret_cast<const float*>(data_[i]->data());
+  matrix_ = new lshkit::FloatMatrix(dim_, static_cast<int>(this->data_.size()));
+  for (size_t i = 0; i < this->data_.size(); ++i) {
+    CHECK(datalength == this->data_[i]->datalength());
+    const float* x = reinterpret_cast<const float*>(this->data_[i]->data());
     for (int j = 0; j < dim_; ++j) {
       (*matrix_)[i][j] = x[j];
     }
@@ -188,7 +188,7 @@ void MultiProbeLSH<dist_t>::Search(KNNQuery<dist_t>* query, IdType) const {
   const lshkit::Topk<uint32_t>& knn = query_scanner.topk();
   for (size_t i = 0; i < knn.size(); ++i) {
     if (knn[i].key != std::numeric_limits<uint32_t>::max()) {
-      query->CheckAndAddToResult(sqrt(knn[i].dist), data_[knn[i].key]);
+      query->CheckAndAddToResult(sqrt(knn[i].dist), this->data_[knn[i].key]);
     }
   }
 }
diff --git a/similarity_search/src/method/nndes.cc b/similarity_search/src/method/nndes.cc
index a8fc7f4..839348b 100644
--- a/similarity_search/src/method/nndes.cc
+++ b/similarity_search/src/method/nndes.cc
@@ -67,7 +67,8 @@ NNDescentMethod<dist_t>::NNDescentMethod(
     bool  PrintProgress,
     const Space<dist_t>& space,
     const ObjectVector& data) :
-      space_(space), data_(data), PrintProgress_(PrintProgress),
+      Index<dist_t>(data),
+      space_(space), PrintProgress_(PrintProgress),
       controlQty_(0), // default value from Wei Dong's code
       nndesOracle_(space, data)
 {}
@@ -92,17 +93,17 @@ void NNDescentMethod<dist_t>::CreateIndex(const AnyParams& IndexParams) {
 
   LOG(LIB_INFO) << "Starting NN-Descent...";
 
-  nndesObj_.reset(new NNDescent<SpaceOracle>(data_.size(), // N
+  nndesObj_.reset(new NNDescent<SpaceOracle>(this->data_.size(), // N
                                              NN_, //K 
                                              rho_, //S, 
                                              nndesOracle_, GRAPH_BOTH));
 
-    float total = float(data_.size()) * (data_.size() - 1) / 2;
+    float total = float(this->data_.size()) * (this->data_.size() - 1) / 2;
     cout.precision(5);
     cout.setf(ios::fixed);
     for (int it = 0; it < iterationQty_; ++it) {
         int t = nndesObj_->iterate(PrintProgress_);
-        float rate = float(t) / (NN_ * data_.size());
+        float rate = float(t) / (NN_ * this->data_.size());
 
 // TODO @leo computation of recall needs to be re-written, can't use original Wei Dong's code
 /*
@@ -140,7 +141,7 @@ void NNDescentMethod<dist_t>::SearchSmallWorld(KNNQuery<dist_t>* query) const {
   const vector<KNN> &nn = nndesObj_->getNN();
 
 #if USE_BITSET_FOR_SEARCHING
-  vector<bool>                      visitedBitset(data_.size());
+  vector<bool>                      visitedBitset(this->data_.size());
 #else
   unordered_set <IdType>            visitedNodes;
 #endif
@@ -149,12 +150,12 @@ void NNDescentMethod<dist_t>::SearchSmallWorld(KNNQuery<dist_t>* query) const {
   /**
    * Search of most k-closest elements to the query.
    */
-    IdType randPoint = RandomInt() % data_.size();
+    IdType randPoint = RandomInt() % this->data_.size();
 
     priority_queue <dist_t>             closestDistQueue; //The set of all elements which distance was calculated
     priority_queue <EvaluatedNode>      candidateSet; //the set of elements which we can use to evaluate
 
-    const Object* currObj = data_[randPoint];
+    const Object* currObj = this->data_[randPoint];
     dist_t         d = query->DistanceObjLeft(currObj);
     query->CheckAndAddToResult(d, currObj);
     
@@ -195,7 +196,7 @@ void NNDescentMethod<dist_t>::SearchSmallWorld(KNNQuery<dist_t>* query) const {
             visitedNodes.insert(currNew);
 #endif
 
-            currObj = data_[currNew];
+            currObj = this->data_[currNew];
             d = query->DistanceObjLeft(currObj);
             query->CheckAndAddToResult(d, currObj);
             EvaluatedNode  evE1(-d, currNew);
@@ -217,10 +218,10 @@ void NNDescentMethod<dist_t>::SearchGreedy(KNNQuery<dist_t>* query) const {
   const vector<KNN> &nn = nndesObj_->getNN();
 
   for (size_t i=0; i < initSearchAttempts_; i++) {
-    IdType curr = RandomInt() % data_.size();
+    IdType curr = RandomInt() % this->data_.size();
 
-    dist_t currDist = query->DistanceObjLeft(data_[curr]);
-    query->CheckAndAddToResult(currDist, data_[curr]);
+    dist_t currDist = query->DistanceObjLeft(this->data_[curr]);
+    query->CheckAndAddToResult(currDist, this->data_[curr]);
 
 
     IdType currOld;
@@ -231,8 +232,8 @@ void NNDescentMethod<dist_t>::SearchGreedy(KNNQuery<dist_t>* query) const {
       for (const KNNEntry&e: nn[currOld]) {
         IdType currNew = e.key;
         if (currNew != KNNEntry::BAD) {
-          dist_t currDistNew = query->DistanceObjLeft(data_[currNew]);
-          query->CheckAndAddToResult(currDistNew, data_[currNew]);
+          dist_t currDistNew = query->DistanceObjLeft(this->data_[currNew]);
+          query->CheckAndAddToResult(currDistNew, this->data_[currNew]);
           if (currDistNew < currDist) {
             curr = currNew;
             currDist = currDistNew;