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
 123     clear()
 124     {
 125         for (unsigned long i = 0; i <= max_index; ++i)
 126             table[i] = init_value;
 127     }
 128
 129     //  Record the ACTUAL result... and indicate whether the prediction
 130     //  corresponding to this event was correct
 131     void record(unsigned long _index, unsigned _val, unsigned _predicted,
 132                 unsigned _pdata)
 133     {
 134         record(_index, _val, _predicted);
 135     }
 136
 137     void record(unsigned long _index, unsigned _val, unsigned _predicted) {
 138         unsigned long index = _index & max_index;
 139
 140         if (_val) {
 141             update_one(table[index]);
 142             ++record_one;
 143
 144             if (_predicted)
 145                 ++correct_pred_one;
 146         } else {
 147             update_zero(table[index]);
 148             ++record_zero;
 149
 150             if (!_predicted)
 151                 ++correct_pred_zero;
 152         }
 153     }
 154
 155     unsigned value(unsigned long _index) {
 156         unsigned long index = _index & max_index;
 157
 158         return table[index];
 159     }
 160
 161
 162     unsigned predict(unsigned long _index, unsigned &pdata) {
 163         return predict(_index);
 164     }
 165
 166     unsigned predict(unsigned long _index) {
 167         unsigned long index = _index & max_index;
 168
 169         if (pred_one(table[index])) {
 170             ++predicted_one;
 171             return 1;
 172         }
 173
 174         ++predicted_zero;
 175         return 0;
 176     }
 177
 178     //  No internal state is changed here
 179     unsigned peek(unsigned long _index) {
 180         unsigned long index = _index & max_index;
 181
 182         if (pred_one(table[index]))
 183             return 1;
 184
 185         return 0;
 186     }
 187
 188
 189     //=======================================================
 190     void regStats();
 191     void regFormulas();
 192 };
 193
 194
 195 #endif // __SAT_COUNTER_HH__