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.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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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 *
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23 */
24
25 #ifndef SHARE_VM_UTILITIES_NUMBERSEQ_HPP
26 #define SHARE_VM_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 0.7
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 // HDR sequence stores the low-resolution high-dynamic-range values.
108 // It does so by maintaining the double array, where first array defines
109 // the magnitude of the value being stored, and the second array maintains
110 // the low resolution histogram within that magnitude. For example, storing
111 // 4.352819 * 10^3 increments the bucket _hdr[3][435]. This allows for
112 // memory efficient storage of huge amount of samples.
113 //
114 // Accepts positive numbers only.
115 class HdrSeq: public NumberSeq {
116 private:
117 enum PrivateConstants {
118 ValBuckets = 512,
119 MagBuckets = 24,
120 MagMinimum = -12,
121 };
122 int** _hdr;
123
124 public:
125 HdrSeq();
126 ~HdrSeq();
127
128 virtual void add(double val);
129 double percentile(double level) const;
130 };
131
132 // Binary magnitude sequence stores the power-of-two histogram.
133 // It has very low memory requirements, and is thread-safe. When accuracy
134 // is not needed, it is preferred over HdrSeq.
135 class BinaryMagnitudeSeq {
136 private:
137 jlong _sum;
138 jlong* _mags;
139
140 public:
141 BinaryMagnitudeSeq();
142 ~BinaryMagnitudeSeq();
143
144 void add(size_t val);
145 size_t num() const;
146 size_t level(int level) const;
147 size_t sum() const;
148 int min_level() const;
149 int max_level() const;
150 };
151
152 class TruncatedSeq: public AbsSeq {
153 private:
154 enum PrivateConstants {
155 DefaultSeqLength = 10
156 };
157 void init();
158 protected:
159 double *_sequence; // buffers the last L elements in the sequence
160 int _length; // this is L
161 int _next; // oldest slot in the array, i.e. next to be overwritten
162
163 public:
164 // accepts a value for L
165 TruncatedSeq(int length = DefaultSeqLength,
166 double alpha = DEFAULT_ALPHA_VALUE);
167 ~TruncatedSeq();
168 virtual void add(double val);
169 virtual double maximum() const;
170 virtual double last() const; // the last value added to the sequence
171
172 double oldest() const; // the oldest valid value in the sequence
173 double predict_next() const; // prediction based on linear regression
174
175 // Debugging/Printing
176 virtual void dump_on(outputStream* s);
177 };
178
179 #endif // SHARE_VM_UTILITIES_NUMBERSEQ_HPP