a correct version

regrank/xgboost_regrank_data.h

@@ -57,7 +57,7 @@ namespace xgboost{
             DMatrix(void){}
             /*! \brief get the number of instances */
             inline size_t Size() const{
-                return info.labels.size();
+                return data.NumRow();
             }           
             /*!
              * \brief load from text file

regrank/xgboost_regrank_eval.h

@@ -110,6 +110,7 @@ namespace xgboost{
             virtual float Eval(const std::vector<float> &preds,
                                const DMatrix::Info &info) const {
                 const unsigned ndata = static_cast<unsigned>(preds.size());
+                utils::Assert( info.weights.size() == ndata, "we need weight to evaluate ams");
                 std::vector< std::pair<float, unsigned> > rec(ndata);
                 
                 #pragma omp parallel for schedule( static )