src/base/sat_counter.hh

   1 /*
   2  * Copyright (c) 2001-2005 The Regents of The University of Michigan
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  *
  28  * Authors: Steve Raasch
  29  *          Steve Reinhardt
  30  */
  31
  32 #ifndef __SAT_COUNTER_HH__
  33 #define __SAT_COUNTER_HH__
  34
  35 #include <string>
  36
  37 #include "base/predictor.hh"
  38
  39 #include "base/statistics.hh"
  40 #include "sim/stats.hh"
  41
  42 //
  43 //
  44 //  A simple saturating counter predictor
  45 //
  46 //
  47 class SaturatingCounterPred : public GenericPredictor
  48 {
  49   private:
  50     std::string   pred_name;
  51     std::string   zero_name;
  52     std::string   one_name;
  53
  54     unsigned index_bits;
  55     unsigned counter_bits;
  56     unsigned zero_change;
  57     unsigned one_change;
  58     unsigned thresh;
  59     unsigned init_value;
  60
  61     unsigned max_value;       // maximum counter value
  62
  63     unsigned long max_index;  // also the index mask value
  64     unsigned *table;
  65
  66     //  Statistics
  67     Stats::Scalar predicted_one;      // Total predictions of one, preds_one
  68     Stats::Scalar predicted_zero;     // Total predictions of zero, preds_zero
  69     Stats::Scalar correct_pred_one;   // Total correct predictions of one, correct_one
  70     Stats::Scalar correct_pred_zero;  // Total correct predictions of zero, correct_zero
  71
  72     Stats::Scalar record_zero;        //updates_zero
  73     Stats::Scalar record_one;         //updates_one
  74
  75     Stats::Formula preds_total;
  76     Stats::Formula pred_frac_zero;
  77     Stats::Formula pred_frac_one;
  78     Stats::Formula correct_total;
  79     Stats::Formula updates_total;
  80     Stats::Formula pred_rate;
  81     Stats::Formula frac_correct_zero;
  82     Stats::Formula frac_correct_one;
  83     Stats::Formula coverage_zero;
  84     Stats::Formula coverage_one;
  85
  86   private:
  87     bool pred_one(unsigned &counter)  { return counter >  thresh; }
  88     bool pred_zero(unsigned &counter) { return counter <= thresh; }
  89
  90     void update_one(unsigned &counter) {
  91
  92         if (one_change)
  93             counter += one_change;
  94         else
  95             counter = 0;
  96
  97         // check for wrap
  98         if (counter > max_value)
  99             counter = max_value;
 100     }
 101
 102     void update_zero(unsigned &counter) {
 103         if (zero_change) {
 104             // check for wrap
 105             if (counter < zero_change)
 106                 counter = 0;
 107             else
 108                 counter -= zero_change;
 109         } else
 110             counter = 0;
 111     }
 112
 113
 114   public:
 115
 116     SaturatingCounterPred(std::string p_name,
 117                           std::string z_name, std::string o_name,
 118                           unsigned _index_bits, unsigned _counter_bits = 2,
 119                           unsigned _zero_change = 1, unsigned _one_change = 1,
 120                           unsigned _thresh = 1, unsigned _init_value = 0);
 121
 122     void clear() {
 123         for (int i = 0; i <= max_index; ++i)
 124             table[i] = init_value;
 125     }
 126
 127     //  Record the ACTUAL result... and indicate whether the prediction
 128     //  corresponding to this event was correct
 129     void record(unsigned long _index, unsigned _val, unsigned _predicted,
 130                 unsigned _pdata)
 131     {
 132         record(_index, _val, _predicted);
 133     }
 134
 135     void record(unsigned long _index, unsigned _val, unsigned _predicted) {
 136         unsigned long index = _index & max_index;
 137
 138         if (_val) {
 139             update_one(table[index]);
 140             ++record_one;
 141
 142             if (_predicted)
 143                 ++correct_pred_one;
 144         } else {
 145             update_zero(table[index]);
 146             ++record_zero;
 147
 148             if (!_predicted)
 149                 ++correct_pred_zero;
 150         }
 151     }
 152
 153     unsigned value(unsigned long _index) {
 154         unsigned long index = _index & max_index;
 155
 156         return table[index];
 157     }
 158
 159
 160     unsigned predict(unsigned long _index, unsigned &pdata) {
 161         return predict(_index);
 162     }
 163
 164     unsigned predict(unsigned long _index) {
 165         unsigned long index = _index & max_index;
 166
 167         if (pred_one(table[index])) {
 168             ++predicted_one;
 169             return 1;
 170         }
 171
 172         ++predicted_zero;
 173         return 0;
 174     }
 175
 176     //  No internal state is changed here
 177     unsigned peek(unsigned long _index) {
 178         unsigned long index = _index & max_index;
 179
 180         if (pred_one(table[index]))
 181             return 1;
 182
 183         return 0;
 184     }
 185
 186
 187     //=======================================================
 188     void regStats();
 189     void regFormulas();
 190 };
 191
 192
 193 #endif // __SAT_COUNTER_HH__