1 /*
   2  * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_UTILITIES_NUMBERSEQ_HPP
  26 #define SHARE_VM_UTILITIES_NUMBERSEQ_HPP
  27 
  28 /**
  29  **  This file contains a few classes that represent number sequence,
  30  **  x1, x2, x3, ..., xN, and can calculate their avg, max, and sd.
  31  **
  32  **  Here's a quick description of the classes:
  33  **
  34  **    AbsSeq: abstract superclass
  35  **    NumberSeq: the sequence is assumed to be very long and the
  36  **      maximum, avg, sd, davg, and dsd are calculated over all its elements
  37  **    TruncatedSeq: this class keeps track of the last L elements
  38  **      of the sequence and calculates avg, max, and sd only over them
  39  **/
  40 
  41 #define DEFAULT_ALPHA_VALUE 0.7
  42 
  43 class AbsSeq {
  44 private:
  45   void init(double alpha);
  46 
  47 protected:
  48   int    _num; // the number of elements in the sequence
  49   double _sum; // the sum of the elements in the sequence
  50   double _sum_of_squares; // the sum of squares of the elements in the sequence
  51 
  52   double _davg; // decaying average
  53   double _dvariance; // decaying variance
  54   double _alpha; // factor for the decaying average / variance
  55 
  56   // This is what we divide with to get the average. In a standard
  57   // number sequence, this should just be the number of elements in it.
  58   virtual double total() const { return (double) _num; };
  59 
  60 public:
  61   AbsSeq(double alpha = DEFAULT_ALPHA_VALUE);
  62 
  63   virtual void add(double val); // adds a new element to the sequence
  64   void add(unsigned val) { add((double) val); }
  65   virtual double maximum() const = 0; // maximum element in the sequence
  66   virtual double last() const = 0; // last element added in the sequence
  67 
  68   // the number of elements in the sequence
  69   int num() const { return _num; }
  70   // the sum of the elements in the sequence
  71   double sum() const { return _sum; }
  72 
  73   double avg() const; // the average of the sequence
  74   double variance() const; // the variance of the sequence
  75   double sd() const; // the standard deviation of the sequence
  76 
  77   double davg() const; // decaying average
  78   double dvariance() const; // decaying variance
  79   double dsd() const; // decaying "standard deviation"
  80 
  81   // Debugging/Printing
  82   virtual void dump();
  83   virtual void dump_on(outputStream* s);
  84 };
  85 
  86 class NumberSeq: public AbsSeq {
  87 private:
  88   bool check_nums(NumberSeq* total, int n, NumberSeq** parts);
  89 
  90 protected:
  91   double _last;
  92   double _maximum; // keep track of maximum value
  93 
  94 public:
  95   NumberSeq(double alpha = DEFAULT_ALPHA_VALUE);

  96 
  97   virtual void add(double val);
  98   virtual double maximum() const { return _maximum; }
  99   virtual double last() const { return _last; }
 100 
 101   // Debugging/Printing
 102   virtual void dump_on(outputStream* s);
 103 };
 104 
 105 class TruncatedSeq: public AbsSeq {
 106 private:
 107   enum PrivateConstants {
 108     DefaultSeqLength = 10
 109   };
 110   void init();
 111 protected:
 112   double *_sequence; // buffers the last L elements in the sequence
 113   int     _length; // this is L
 114   int     _next;   // oldest slot in the array, i.e. next to be overwritten
 115 
 116 public:
 117   // accepts a value for L
 118   TruncatedSeq(int length = DefaultSeqLength,
 119                double alpha = DEFAULT_ALPHA_VALUE);
 120   ~TruncatedSeq();
 121   virtual void add(double val);
 122   virtual double maximum() const;
 123   virtual double last() const; // the last value added to the sequence
 124 
 125   double oldest() const; // the oldest valid value in the sequence
 126   double predict_next() const; // prediction based on linear regression
 127 
 128   // Debugging/Printing
 129   virtual void dump_on(outputStream* s);
 130 };
 131 
 132 #endif // SHARE_VM_UTILITIES_NUMBERSEQ_HPP
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