src/bench/bench.cpp

   1 // Copyright (c) 2015-2016 The Bitcoin Core developers
   2 // Distributed under the MIT software license, see the accompanying
   3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4
   5 #include "bench.h"
   6 #include "perf.h"
   7
   8 #include <assert.h>
   9 #include <iostream>
  10 #include <iomanip>
  11 #include <sys/time.h>
  12
  13 benchmark::BenchRunner::BenchmarkMap &benchmark::BenchRunner::benchmarks() {
  14     static std::map<std::string, benchmark::BenchFunction> benchmarks_map;
  15     return benchmarks_map;
  16 }
  17
  18 static double gettimedouble(void) {
  19     struct timeval tv;
  20     gettimeofday(&tv, nullptr);
  21     return tv.tv_usec * 0.000001 + tv.tv_sec;
  22 }
  23
  24 benchmark::BenchRunner::BenchRunner(std::string name, benchmark::BenchFunction func)
  25 {
  26     benchmarks().insert(std::make_pair(name, func));
  27 }
  28
  29 void
  30 benchmark::BenchRunner::RunAll(double elapsedTimeForOne)
  31 {
  32     perf_init();
  33     std::cout << "#Benchmark" << "," << "count" << "," << "min" << "," << "max" << "," << "average" << ","
  34               << "min_cycles" << "," << "max_cycles" << "," << "average_cycles" << "\n";
  35
  36     for (const auto &p: benchmarks()) {
  37         State state(p.first, elapsedTimeForOne);
  38         p.second(state);
  39     }
  40     perf_fini();
  41 }
  42
  43 bool benchmark::State::KeepRunning()
  44 {
  45     if (count & countMask) {
  46       ++count;
  47       return true;
  48     }
  49     double now;
  50     uint64_t nowCycles;
  51     if (count == 0) {
  52         lastTime = beginTime = now = gettimedouble();
  53         lastCycles = beginCycles = nowCycles = perf_cpucycles();
  54     }
  55     else {
  56         now = gettimedouble();
  57         double elapsed = now - lastTime;
  58         double elapsedOne = elapsed * countMaskInv;
  59         if (elapsedOne < minTime) minTime = elapsedOne;
  60         if (elapsedOne > maxTime) maxTime = elapsedOne;
  61
  62         // We only use relative values, so don't have to handle 64-bit wrap-around specially
  63         nowCycles = perf_cpucycles();
  64         uint64_t elapsedOneCycles = (nowCycles - lastCycles) * countMaskInv;
  65         if (elapsedOneCycles < minCycles) minCycles = elapsedOneCycles;
  66         if (elapsedOneCycles > maxCycles) maxCycles = elapsedOneCycles;
  67
  68         if (elapsed*128 < maxElapsed) {
  69           // If the execution was much too fast (1/128th of maxElapsed), increase the count mask by 8x and restart timing.
  70           // The restart avoids including the overhead of this code in the measurement.
  71           countMask = ((countMask<<3)|7) & ((1LL<<60)-1);
  72           countMaskInv = 1./(countMask+1);
  73           count = 0;
  74           minTime = std::numeric_limits<double>::max();
  75           maxTime = std::numeric_limits<double>::min();
  76           minCycles = std::numeric_limits<uint64_t>::max();
  77           maxCycles = std::numeric_limits<uint64_t>::min();
  78           return true;
  79         }
  80         if (elapsed*16 < maxElapsed) {
  81           uint64_t newCountMask = ((countMask<<1)|1) & ((1LL<<60)-1);
  82           if ((count & newCountMask)==0) {
  83               countMask = newCountMask;
  84               countMaskInv = 1./(countMask+1);
  85           }
  86         }
  87     }
  88     lastTime = now;
  89     lastCycles = nowCycles;
  90     ++count;
  91
  92     if (now - beginTime < maxElapsed) return true; // Keep going
  93
  94     --count;
  95
  96     assert(count != 0 && "count == 0 => (now == 0 && beginTime == 0) => return above");
  97
  98     // Output results
  99     double average = (now-beginTime)/count;
 100     int64_t averageCycles = (nowCycles-beginCycles)/count;
 101     std::cout << std::fixed << std::setprecision(15) << name << "," << count << "," << minTime << "," << maxTime << "," << average << ","
 102               << minCycles << "," << maxCycles << "," << averageCycles << "\n";
 103     std::cout.copyfmt(std::ios(nullptr));
 104
 105     return false;
 106 }