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
  12 benchmark::BenchRunner::BenchmarkMap &benchmark::BenchRunner::benchmarks() {
  13     static std::map<std::string, benchmark::BenchFunction> benchmarks_map;
  14     return benchmarks_map;
  15 }
  16
  17 benchmark::BenchRunner::BenchRunner(std::string name, benchmark::BenchFunction func)
  18 {
  19     benchmarks().insert(std::make_pair(name, func));
  20 }
  21
  22 void
  23 benchmark::BenchRunner::RunAll(benchmark::duration elapsedTimeForOne)
  24 {
  25     perf_init();
  26     std::cout << "#Benchmark" << "," << "count" << "," << "min(ns)" << "," << "max(ns)" << "," << "average(ns)" << ","
  27               << "min_cycles" << "," << "max_cycles" << "," << "average_cycles" << "\n";
  28
  29     for (const auto &p: benchmarks()) {
  30         State state(p.first, elapsedTimeForOne);
  31         p.second(state);
  32     }
  33     perf_fini();
  34 }
  35
  36 bool benchmark::State::KeepRunning()
  37 {
  38     if (count & countMask) {
  39       ++count;
  40       return true;
  41     }
  42     time_point now;
  43
  44     uint64_t nowCycles;
  45     if (count == 0) {
  46         lastTime = beginTime = now = clock::now();
  47         lastCycles = beginCycles = nowCycles = perf_cpucycles();
  48     }
  49     else {
  50         now = clock::now();
  51         auto elapsed = now - lastTime;
  52         auto elapsedOne = elapsed / (countMask + 1);
  53         if (elapsedOne < minTime) minTime = elapsedOne;
  54         if (elapsedOne > maxTime) maxTime = elapsedOne;
  55
  56         // We only use relative values, so don't have to handle 64-bit wrap-around specially
  57         nowCycles = perf_cpucycles();
  58         uint64_t elapsedOneCycles = (nowCycles - lastCycles) / (countMask + 1);
  59         if (elapsedOneCycles < minCycles) minCycles = elapsedOneCycles;
  60         if (elapsedOneCycles > maxCycles) maxCycles = elapsedOneCycles;
  61
  62         if (elapsed*128 < maxElapsed) {
  63           // If the execution was much too fast (1/128th of maxElapsed), increase the count mask by 8x and restart timing.
  64           // The restart avoids including the overhead of this code in the measurement.
  65           countMask = ((countMask<<3)|7) & ((1LL<<60)-1);
  66           count = 0;
  67           minTime = duration::max();
  68           maxTime = duration::zero();
  69           minCycles = std::numeric_limits<uint64_t>::max();
  70           maxCycles = std::numeric_limits<uint64_t>::min();
  71           return true;
  72         }
  73         if (elapsed*16 < maxElapsed) {
  74           uint64_t newCountMask = ((countMask<<1)|1) & ((1LL<<60)-1);
  75           if ((count & newCountMask)==0) {
  76               countMask = newCountMask;
  77           }
  78         }
  79     }
  80     lastTime = now;
  81     lastCycles = nowCycles;
  82     ++count;
  83
  84     if (now - beginTime < maxElapsed) return true; // Keep going
  85
  86     --count;
  87
  88     assert(count != 0 && "count == 0 => (now == 0 && beginTime == 0) => return above");
  89
  90     // Output results
  91     // Duration casts are only necessary here because hardware with sub-nanosecond clocks
  92     // will lose precision.
  93     int64_t min_elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(minTime).count();
  94     int64_t max_elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(maxTime).count();
  95     int64_t avg_elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>((now-beginTime)/count).count();
  96     int64_t averageCycles = (nowCycles-beginCycles)/count;
  97     std::cout << std::fixed << std::setprecision(15) << name << "," << count << "," << min_elapsed << "," << max_elapsed << "," << avg_elapsed << ","
  98               << minCycles << "," << maxCycles << "," << averageCycles << "\n";
  99     std::cout.copyfmt(std::ios(nullptr));
 100
 101     return false;
 102 }