src/StatHist.h

   1 /*
   2  * AUTHOR: Francesco Chemolli
   3  *
   4  * SQUID Web Proxy Cache          http://www.squid-cache.org/
   5  * ----------------------------------------------------------
   6  *
   7  *  Squid is the result of efforts by numerous individuals from
   8  *  the Internet community; see the CONTRIBUTORS file for full
   9  *  details.   Many organizations have provided support for Squid's
  10  *  development; see the SPONSORS file for full details.  Squid is
  11  *  Copyrighted (C) 2001 by the Regents of the University of
  12  *  California; see the COPYRIGHT file for full details.  Squid
  13  *  incorporates software developed and/or copyrighted by other
  14  *  sources; see the CREDITS file for full details.
  15  *
  16  *  This program is free software; you can redistribute it and/or modify
  17  *  it under the terms of the GNU General Public License as published by
  18  *  the Free Software Foundation; either version 2 of the License, or
  19  *  (at your option) any later version.
  20  *
  21  *  This program is distributed in the hope that it will be useful,
  22  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  23  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  24  *  GNU General Public License for more details.
  25  *
  26  *  You should have received a copy of the GNU General Public License
  27  *  along with this program; if not, write to the Free Software
  28  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  29  */
  30
  31 #ifndef STATHIST_H_
  32 #define STATHIST_H_
  33
  34 /* for StoreEntry */
  35 #include "Store.h"
  36
  37
  38 /// function signature for in/out StatHist adaptation
  39 typedef double hbase_f(double);
  40
  41 /// function signature for StatHist dumping functions
  42 typedef void StatHistBinDumper(StoreEntry *, int idx, double val, double size, int count);
  43
  44 /** Generic histogram class
  45  *
  46  * see important comments on hbase_f restrictions in StatHist.cc
  47  */
  48 class StatHist {
  49 public:
  50     /**
  51      * \note the default constructor doesn't fully initialize.
  52      *       you have to call one of the *init functions to specialize the
  53      *       histogram
  54      * \todo merge functionality from the *init functions to the constructor and
  55      *       drop these
  56      * \todo specialize the class in a small hierarchy so that all
  57      *       relevant initializations are done at build-time
  58      */
  59     StatHist() : scale_(1.0) {};
  60     StatHist(const StatHist&);
  61     StatHist &operator=(const StatHist &);
  62     virtual ~StatHist();
  63     /** clear the contents of the histograms
  64      *
  65      * \todo remove: this function has been replaced in its purpose
  66      *       by the destructor
  67      */
  68     void clear();
  69
  70     /** Calculate the percentile for value pctile for the difference between
  71      *  this and the supplied histogram.
  72      */
  73     double deltaPctile(const StatHist &B, double pctile) const;
  74     /** obtain the output-transformed value from the specified bin
  75      *
  76      */
  77     double val(int bin) const;
  78     /** increment the counter for the histogram entry
  79      * associated to the supplied value
  80      */
  81     void count(double val);
  82     /** iterate the supplied bd function over the histogram values
  83      */
  84     void dump(StoreEntry *sentry, StatHistBinDumper * bd) const;
  85     /** Initialize the Histogram using a logarithmic values distribution
  86      *
  87      */
  88     void logInit(int capacity, double min, double max);
  89     /** initialize the histogram to count occurrences in an enum-represented set
  90      *
  91      */
  92     void enumInit(int last_enum);
  93 protected:
  94     /** low-level initialize function. called by *Init high-level functions
  95      * \note Important restrictions on val_in and val_out functions:
  96      *
  97      *   - val_in:  ascending, defined on [0, oo), val_in(0) == 0;
  98      *   - val_out: x == val_out(val_in(x)) where val_in(x) is defined
  99      *
 100      *  In practice, the requirements are less strict,
 101      *  but then it gets hard to define them without math notation.
 102      *  val_in is applied after offseting the value but before scaling
 103      *  See log and linear based histograms for examples
 104      */
 105     void init(int capacity, hbase_f * val_in, hbase_f * val_out, double min, double max);
 106     /// find what entry in the histogram corresponds to v, by applying
 107     /// the preset input transformation function
 108     int findBin(double v);
 109     /// the histogram counters
 110     int *bins;
 111     int capacity_;
 112     /// minimum value to be stored, corresponding to the first bin
 113     double min_;
 114     /// value of the maximum counter in the histogram
 115     double max_;
 116     /// scaling factor when looking for a bin
 117     double scale_;
 118     hbase_f *val_in;        /* e.g., log() for log-based histogram */
 119     hbase_f *val_out;       /* e.g., exp() for log based histogram */
 120 };
 121
 122 double statHistDeltaMedian(const StatHist & A, const StatHist & B);
 123 double statHistDeltaPctile(const StatHist & A, const StatHist & B, double pctile);
 124 StatHistBinDumper statHistEnumDumper;
 125 StatHistBinDumper statHistIntDumper;
 126
 127 #endif /* STATHIST_H_ */