1 /*
  2  * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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  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
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 24 
 25 #ifndef SHARE_UTILITIES_NUMBERSEQ_HPP
 26 #define SHARE_UTILITIES_NUMBERSEQ_HPP
 27 
 28 #include "memory/allocation.hpp"
 29 
 30 /**
 31  **  This file contains a few classes that represent number sequence,
 32  **  x1, x2, x3, ..., xN, and can calculate their avg, max, and sd.
 33  **
 34  **  Here's a quick description of the classes:
 35  **
 36  **    AbsSeq: abstract superclass
 37  **    NumberSeq: the sequence is assumed to be very long and the
 38  **      maximum, avg, sd, davg, and dsd are calculated over all its elements
 39  **    TruncatedSeq: this class keeps track of the last L elements
 40  **      of the sequence and calculates avg, max, and sd only over them
 41  **/
 42 
 43 #define DEFAULT_ALPHA_VALUE 0.3
 44 
 45 class AbsSeq: public CHeapObj<mtInternal> {
 46 private:
 47   void init(double alpha);
 48 
 49 protected:
 50   int    _num; // the number of elements in the sequence
 51   double _sum; // the sum of the elements in the sequence
 52   double _sum_of_squares; // the sum of squares of the elements in the sequence
 53 
 54   double _davg; // decaying average
 55   double _dvariance; // decaying variance
 56   double _alpha; // factor for the decaying average / variance
 57 
 58   // This is what we divide with to get the average. In a standard
 59   // number sequence, this should just be the number of elements in it.
 60   virtual double total() const { return (double) _num; };
 61 
 62 public:
 63   AbsSeq(double alpha = DEFAULT_ALPHA_VALUE);
 64 
 65   virtual void add(double val); // adds a new element to the sequence
 66   void add(unsigned val) { add((double) val); }
 67   virtual double maximum() const = 0; // maximum element in the sequence
 68   virtual double last() const = 0; // last element added in the sequence
 69 
 70   // the number of elements in the sequence
 71   int num() const { return _num; }
 72   // the sum of the elements in the sequence
 73   double sum() const { return _sum; }
 74 
 75   double avg() const; // the average of the sequence
 76   double variance() const; // the variance of the sequence
 77   double sd() const; // the standard deviation of the sequence
 78 
 79   double davg() const; // decaying average
 80   double dvariance() const; // decaying variance
 81   double dsd() const; // decaying "standard deviation"
 82 
 83   // Debugging/Printing
 84   virtual void dump();
 85   virtual void dump_on(outputStream* s);
 86 };
 87 
 88 class NumberSeq: public AbsSeq {
 89 private:
 90   bool check_nums(NumberSeq* total, int n, NumberSeq** parts);
 91 
 92 protected:
 93   double _last;
 94   double _maximum; // keep track of maximum value
 95 
 96 public:
 97   NumberSeq(double alpha = DEFAULT_ALPHA_VALUE);
 98 
 99   virtual void add(double val);
100   virtual double maximum() const { return _maximum; }
101   virtual double last() const { return _last; }
102 
103   // Debugging/Printing
104   virtual void dump_on(outputStream* s);
105 };
106 
107 class TruncatedSeq: public AbsSeq {
108 private:
109   enum PrivateConstants {
110     DefaultSeqLength = 10
111   };
112   void init();
113 protected:
114   double *_sequence; // buffers the last L elements in the sequence
115   int     _length; // this is L
116   int     _next;   // oldest slot in the array, i.e. next to be overwritten
117 
118 public:
119   // accepts a value for L
120   TruncatedSeq(int length = DefaultSeqLength,
121                double alpha = DEFAULT_ALPHA_VALUE);
122   ~TruncatedSeq();
123   virtual void add(double val);
124   virtual double maximum() const;
125   virtual double last() const; // the last value added to the sequence
126 
127   double oldest() const; // the oldest valid value in the sequence
128   double predict_next() const; // prediction based on linear regression
129 
130   // Debugging/Printing
131   virtual void dump_on(outputStream* s);
132 };
133 
134 #endif // SHARE_UTILITIES_NUMBERSEQ_HPP