From 8234091368770126f997a1f8d147e1b855243b39 Mon Sep 17 00:00:00 2001
From: Jiaming Yuan <jm.yuan@outlook.com>
Date: Tue, 23 Jun 2020 14:27:46 +0800
Subject: [PATCH] Remove unweighted GK quantile. (#5816)

---
 src/common/quantile.h | 155 ------------------------------------------
 1 file changed, 155 deletions(-)

diff --git a/src/common/quantile.h b/src/common/quantile.h
index 067b041bc..c0079ff8e 100644
--- a/src/common/quantile.h
+++ b/src/common/quantile.h
@@ -445,152 +445,6 @@ struct WXQSummary : public WQSummary<DType, RType> {
     }
   }
 };
-/*!
- * \brief traditional GK summary
- */
-template<typename DType, typename RType>
-struct GKSummary {
-  /*! \brief an entry in the sketch summary */
-  struct Entry {
-    /*! \brief minimum rank */
-    RType rmin;
-    /*! \brief maximum rank */
-    RType rmax;
-    /*! \brief the value of data */
-    DType value;
-    // constructor
-    Entry() = default;
-    // constructor
-    Entry(RType rmin, RType rmax, DType value)
-        : rmin(rmin), rmax(rmax), value(value) {}
-  };
-  /*! \brief input data queue before entering the summary */
-  struct Queue {
-    // the input queue
-    std::vector<DType> queue;
-    // end of the queue
-    size_t qtail;
-    // push data to the queue
-    inline void Push(DType x, RType w) {
-      queue[qtail++] = x;
-    }
-    inline void MakeSummary(GKSummary *out) {
-      std::sort(queue.begin(), queue.begin() + qtail);
-      out->size = qtail;
-      for (size_t i = 0; i < qtail; ++i) {
-        out->data[i] = Entry(i + 1, i + 1, queue[i]);
-      }
-    }
-  };
-  /*! \brief data field */
-  Entry *data;
-  /*! \brief number of elements in the summary */
-  size_t size;
-  GKSummary(Entry *data, size_t size)
-      : data(data), size(size) {}
-  /*! \brief the maximum error of the summary */
-  inline RType MaxError() const {
-    RType res = 0;
-    for (size_t i = 1; i < size; ++i) {
-      res = std::max(data[i].rmax - data[i-1].rmin, res);
-    }
-    return res;
-  }
-  /*! \return maximum rank in the summary */
-  inline RType MaxRank() const {
-    return data[size - 1].rmax;
-  }
-  /*!
-   * \brief copy content from src
-   * \param src source sketch
-   */
-  inline void CopyFrom(const GKSummary &src) {
-    size = src.size;
-    std::memcpy(data, src.data, sizeof(Entry) * size);
-  }
-  inline void CheckValid(RType eps) const {
-    // assume always valid
-  }
-  /*! \brief used for debug purpose, print the summary */
-  inline void Print() const {
-    for (size_t i = 0; i < size; ++i) {
-      LOG(CONSOLE) << "x=" << data[i].value << "\t"
-                   << "[" << data[i].rmin << "," << data[i].rmax << "]";
-    }
-  }
-  /*!
-   * \brief set current summary to be pruned summary of src
-   *        assume data field is already allocated to be at least maxsize
-   * \param src source summary
-   * \param maxsize size we can afford in the pruned sketch
-   */
-  inline void SetPrune(const GKSummary &src, size_t maxsize) {
-    if (src.size <= maxsize) {
-      this->CopyFrom(src); return;
-    }
-    const RType max_rank = src.MaxRank();
-    this->size = maxsize;
-    data[0] = src.data[0];
-    size_t n = maxsize - 1;
-    RType top = 1;
-    for (size_t i = 1; i < n; ++i) {
-      RType k = (i * max_rank) / n;
-      while (k > src.data[top + 1].rmax) ++top;
-      // assert src.data[top].rmin <= k
-      // because k > src.data[top].rmax >= src.data[top].rmin
-      if ((k - src.data[top].rmin) < (src.data[top+1].rmax - k)) {
-        data[i] = src.data[top];
-      } else {
-        data[i] = src.data[top + 1];
-      }
-    }
-    data[n] = src.data[src.size - 1];
-  }
-  inline void SetCombine(const GKSummary &sa,
-                         const GKSummary &sb) {
-    if (sa.size == 0) {
-      this->CopyFrom(sb); return;
-    }
-    if (sb.size == 0) {
-      this->CopyFrom(sa); return;
-    }
-    CHECK(sa.size > 0 && sb.size > 0) << "invalid input for merge";
-    const Entry *a = sa.data, *a_end = sa.data + sa.size;
-    const Entry *b = sb.data, *b_end = sb.data + sb.size;
-    this->size = sa.size + sb.size;
-    RType aprev_rmin = 0, bprev_rmin = 0;
-    Entry *dst = this->data;
-    while (a != a_end && b != b_end) {
-      if (a->value < b->value) {
-        *dst = Entry(bprev_rmin + a->rmin,
-                     a->rmax + b->rmax - 1, a->value);
-        aprev_rmin = a->rmin;
-        ++dst; ++a;
-      } else {
-        *dst = Entry(aprev_rmin + b->rmin,
-                     b->rmax + a->rmax - 1, b->value);
-        bprev_rmin = b->rmin;
-        ++dst; ++b;
-      }
-    }
-    if (a != a_end) {
-      RType bprev_rmax = (b_end - 1)->rmax;
-      do {
-        *dst = Entry(bprev_rmin + a->rmin, bprev_rmax + a->rmax, a->value);
-        ++dst; ++a;
-      } while (a != a_end);
-    }
-    if (b != b_end) {
-      RType aprev_rmax = (a_end - 1)->rmax;
-      do {
-        *dst = Entry(aprev_rmin + b->rmin, aprev_rmax + b->rmax, b->value);
-        ++dst; ++b;
-      } while (b != b_end);
-    }
-    CHECK(dst == data + size) << "bug in combine";
-  }
-};
-
 /*!
  * \brief template for all quantile sketch algorithm
  *        that uses merge/prune scheme
@@ -841,15 +695,6 @@ template<typename DType, typename RType = unsigned>
 class WXQuantileSketch :
       public QuantileSketchTemplate<DType, RType, WXQSummary<DType, RType> > {
 };
-/*!
- * \brief Quantile sketch use WQSummary
- * \tparam DType type of data content
- * \tparam RType type of rank
- */
-template<typename DType, typename RType = unsigned>
-class GKQuantileSketch :
-      public QuantileSketchTemplate<DType, RType, GKSummary<DType, RType> > {
-};
 }  // namespace common
 }  // namespace xgboost
 #endif  // XGBOOST_COMMON_QUANTILE_H_