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/*
* Copyright 2012 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// @author Andrei Alexandrescu (andrei.alexandrescu@fb.com)
#include "Benchmark.h"
#include "Foreach.h"
#include "json.h"
#include "String.h"
#include <algorithm>
#include <boost/regex.hpp>
#include <cmath>
#include <iostream>
#include <limits>
#include <utility>
#include <vector>
using namespace std;
DEFINE_bool(benchmark, false, "Run benchmarks.");
DEFINE_bool(json, false, "Output in JSON format.");
DEFINE_string(bm_regex, "",
"Only benchmarks whose names match this regex will be run.");
DEFINE_int64(bm_min_usec, 100,
"Minimum # of microseconds we'll accept for each benchmark.");
DEFINE_int32(bm_max_secs, 1,
"Maximum # of seconds we'll spend on each benchmark.");
namespace folly {
BenchmarkSuspender::NanosecondsSpent BenchmarkSuspender::nsSpent;
typedef function<uint64_t(unsigned int)> BenchmarkFun;
static vector<tuple<const char*, const char*, BenchmarkFun>> benchmarks;
// Add the global baseline
BENCHMARK(globalBenchmarkBaseline) {
asm volatile("");
}
void detail::addBenchmarkImpl(const char* file, const char* name,
BenchmarkFun fun) {
benchmarks.emplace_back(file, name, std::move(fun));
}
/**
* Given a point, gives density at that point as a number 0.0 < x <=
* 1.0. The result is 1.0 if all samples are equal to where, and
* decreases near 0 if all points are far away from it. The density is
* computed with the help of a radial basis function.
*/
static double density(const double * begin, const double *const end,
const double where, const double bandwidth) {
assert(begin < end);
assert(bandwidth > 0.0);
double sum = 0.0;
FOR_EACH_RANGE (i, begin, end) {
auto d = (*i - where) / bandwidth;
sum += exp(- d * d);
}
return sum / (end - begin);
}
/**
* Computes mean and variance for a bunch of data points. Note that
* mean is currently not being used.
*/
static pair<double, double>
meanVariance(const double * begin, const double *const end) {
assert(begin < end);
double sum = 0.0, sum2 = 0.0;
FOR_EACH_RANGE (i, begin, end) {
sum += *i;
sum2 += *i * *i;
}
auto const n = end - begin;
return make_pair(sum / n, sqrt((sum2 - sum * sum / n) / n));
}
/**
* Computes the mode of a sample set through brute force. Assumes
* input is sorted.
*/
static double mode(const double * begin, const double *const end) {
assert(begin < end);
// Lower bound and upper bound for result and their respective
// densities.
auto
result = 0.0,
bestDensity = 0.0;
// Get the variance so we pass it down to density()
auto const sigma = meanVariance(begin, end).second;
if (!sigma) {
// No variance means constant signal
return *begin;
}
FOR_EACH_RANGE (i, begin, end) {
assert(i == begin || *i >= i[-1]);
auto candidate = density(begin, end, *i, sigma * sqrt(2.0));
if (candidate > bestDensity) {
// Found a new best
bestDensity = candidate;
result = *i;
} else {
// Density is decreasing... we could break here if we definitely
// knew this is unimodal.
}
}
return result;
}
/**
* Given a bunch of benchmark samples, estimate the actual run time.
*/
static double estimateTime(double * begin, double * end) {
assert(begin < end);
// Current state of the art: get the minimum. After some
// experimentation, it seems taking the minimum is the best.
return *min_element(begin, end);
// What follows after estimates the time as the mode of the
// distribution.
// Select the awesomest (i.e. most frequent) result. We do this by
// sorting and then computing the longest run length.
sort(begin, end);
// Eliminate outliers. A time much larger than the minimum time is
// considered an outlier.
while (end[-1] > 2.0 * *begin) {
--end;
if (begin == end) {
LOG(INFO) << *begin;
}
assert(begin < end);
}
double result = 0;
/* Code used just for comparison purposes */ {
unsigned bestFrequency = 0;
unsigned candidateFrequency = 1;
double candidateValue = *begin;
for (auto current = begin + 1; ; ++current) {
if (current == end || *current != candidateValue) {
// Done with the current run, see if it was best
if (candidateFrequency > bestFrequency) {
bestFrequency = candidateFrequency;
result = candidateValue;
}
if (current == end) {
break;
}
// Start a new run
candidateValue = *current;
candidateFrequency = 1;
} else {
// Cool, inside a run, increase the frequency
++candidateFrequency;
}
}
}
result = mode(begin, end);
return result;
}
static double runBenchmarkGetNSPerIteration(const BenchmarkFun& fun,
const double globalBaseline) {
// They key here is accuracy; too low numbers means the accuracy was
// coarse. We up the ante until we get to at least minNanoseconds
// timings.
static uint64_t resolutionInNs = 0, coarseResolutionInNs = 0;
if (!resolutionInNs) {
timespec ts;
CHECK_EQ(0, clock_getres(detail::DEFAULT_CLOCK_ID, &ts));
CHECK_EQ(0, ts.tv_sec) << "Clock sucks.";
CHECK_LT(0, ts.tv_nsec) << "Clock too fast for its own good.";
CHECK_EQ(1, ts.tv_nsec) << "Clock too coarse, upgrade your kernel.";
resolutionInNs = ts.tv_nsec;
}
// We choose a minimum minimum (sic) of 100,000 nanoseconds, but if
// the clock resolution is worse than that, it will be larger. In
// essence we're aiming at making the quantization noise 0.01%.
static const auto minNanoseconds =
max(FLAGS_bm_min_usec * 1000UL, min(resolutionInNs * 100000, 1000000000UL));
// We do measurements in several epochs and take the minimum, to
// account for jitter.
static const unsigned int epochs = 1000;
// We establish a total time budget as we don't want a measurement
// to take too long. This will curtail the number of actual epochs.
const uint64_t timeBudgetInNs = FLAGS_bm_max_secs * 1000000000;
timespec global;
CHECK_EQ(0, clock_gettime(CLOCK_REALTIME, &global));
double epochResults[epochs] = { 0 };
size_t actualEpochs = 0;
for (; actualEpochs < epochs; ++actualEpochs) {
for (unsigned int n = 1; n < (1UL << 30); n *= 2) {
auto const nsecs = fun(n);
if (nsecs < minNanoseconds) {
continue;
}
// We got an accurate enough timing, done. But only save if
// smaller than the current result.
epochResults[actualEpochs] = max(0.0, double(nsecs) / n - globalBaseline);
// Done with the current epoch, we got a meaningful timing.
break;
}
timespec now;
CHECK_EQ(0, clock_gettime(CLOCK_REALTIME, &now));
if (detail::timespecDiff(now, global) >= timeBudgetInNs) {
// No more time budget available.
++actualEpochs;
break;
}
}
// If the benchmark was basically drowned in baseline noise, it's
// possible it became negative.
return max(0.0, estimateTime(epochResults, epochResults + actualEpochs));
}
struct ScaleInfo {
double boundary;
const char* suffix;
};
static const ScaleInfo kTimeSuffixes[] {
{ 365.25 * 24 * 3600, "years" },
{ 24 * 3600, "days" },
{ 3600, "hr" },
{ 60, "min" },
{ 1, "s" },
{ 1E-3, "ms" },
{ 1E-6, "us" },
{ 1E-9, "ns" },
{ 1E-12, "ps" },
{ 1E-15, "fs" },
{ 0, NULL },
};
static const ScaleInfo kMetricSuffixes[] {
{ 1E24, "Y" }, // yotta
{ 1E21, "Z" }, // zetta
{ 1E18, "X" }, // "exa" written with suffix 'X' so as to not create
// confusion with scientific notation
{ 1E15, "P" }, // peta
{ 1E12, "T" }, // terra
{ 1E9, "G" }, // giga
{ 1E6, "M" }, // mega
{ 1E3, "K" }, // kilo
{ 1, "" },
{ 1E-3, "m" }, // milli
{ 1E-6, "u" }, // micro
{ 1E-9, "n" }, // nano
{ 1E-12, "p" }, // pico
{ 1E-15, "f" }, // femto
{ 1E-18, "a" }, // atto
{ 1E-21, "z" }, // zepto
{ 1E-24, "y" }, // yocto
{ 0, NULL },
};
static string humanReadable(double n, unsigned int decimals,
const ScaleInfo* scales) {
if (std::isinf(n) || std::isnan(n)) {
return folly::to<string>(n);
}
const double absValue = fabs(n);
const ScaleInfo* scale = scales;
while (absValue < scale[0].boundary && scale[1].suffix != NULL) {
++scale;
}
const double scaledValue = n / scale->boundary;
return stringPrintf("%.*f%s", decimals, scaledValue, scale->suffix);
}
static string readableTime(double n, unsigned int decimals) {
return humanReadable(n, decimals, kTimeSuffixes);
}
static string metricReadable(double n, unsigned int decimals) {
return humanReadable(n, decimals, kMetricSuffixes);
}
static void printBenchmarkResultsAsTable(
const vector<tuple<const char*, const char*, double> >& data) {
// Width available
static const uint columns = 76;
// Compute the longest benchmark name
size_t longestName = 0;
FOR_EACH_RANGE (i, 1, benchmarks.size()) {
longestName = max(longestName, strlen(get<1>(benchmarks[i])));
}
// Print a horizontal rule
auto separator = [&](char pad) {
puts(string(columns, pad).c_str());
};
// Print header for a file
auto header = [&](const char* file) {
separator('=');
printf("%-*srelative time/iter iters/s\n",
columns - 28, file);
separator('=');
};
double baselineNsPerIter = numeric_limits<double>::max();
const char* lastFile = "";
for (auto& datum : data) {
auto file = get<0>(datum);
if (strcmp(file, lastFile)) {
// New file starting
header(file);
lastFile = file;
}
string s = get<1>(datum);
if (s == "-") {
separator('-');
continue;
}
bool useBaseline /* = void */;
if (s[0] == '%') {
s.erase(0, 1);
useBaseline = true;
} else {
baselineNsPerIter = get<2>(datum);
useBaseline = false;
}
s.resize(columns - 29, ' ');
auto nsPerIter = get<2>(datum);
auto secPerIter = nsPerIter / 1E9;
auto itersPerSec = 1 / secPerIter;
if (!useBaseline) {
// Print without baseline
printf("%*s %9s %7s\n",
static_cast<int>(s.size()), s.c_str(),
readableTime(secPerIter, 2).c_str(),
metricReadable(itersPerSec, 2).c_str());
} else {
// Print with baseline
auto rel = baselineNsPerIter / nsPerIter * 100.0;
printf("%*s %7.2f%% %9s %7s\n",
static_cast<int>(s.size()), s.c_str(),
rel,
readableTime(secPerIter, 2).c_str(),
metricReadable(itersPerSec, 2).c_str());
}
}
separator('=');
}
static void printBenchmarkResultsAsJson(
const vector<tuple<const char*, const char*, double> >& data) {
dynamic d = dynamic::object;
for (auto& datum: data) {
d[std::get<1>(datum)] = std::get<2>(datum) * 1000.;
}
printf("%s\n", toPrettyJson(d).c_str());
}
static void printBenchmarkResults(
const vector<tuple<const char*, const char*, double> >& data) {
if (FLAGS_json) {
printBenchmarkResultsAsJson(data);
} else {
printBenchmarkResultsAsTable(data);
}
}
void runBenchmarks() {
CHECK(!benchmarks.empty());
vector<tuple<const char*, const char*, double>> results;
results.reserve(benchmarks.size() - 1);
std::unique_ptr<boost::regex> bmRegex;
if (!FLAGS_bm_regex.empty()) {
bmRegex.reset(new boost::regex(FLAGS_bm_regex));
}
// PLEASE KEEP QUIET. MEASUREMENTS IN PROGRESS.
auto const globalBaseline = runBenchmarkGetNSPerIteration(
get<2>(benchmarks.front()), 0);
FOR_EACH_RANGE (i, 1, benchmarks.size()) {
double elapsed = 0.0;
if (!strcmp(get<1>(benchmarks[i]), "-") == 0) { // skip separators
if (bmRegex && !boost::regex_search(get<1>(benchmarks[i]), *bmRegex)) {
continue;
}
elapsed = runBenchmarkGetNSPerIteration(get<2>(benchmarks[i]),
globalBaseline);
}
results.emplace_back(get<0>(benchmarks[i]),
get<1>(benchmarks[i]), elapsed);
}
// PLEASE MAKE NOISE. MEASUREMENTS DONE.
printBenchmarkResults(results);
}
} // namespace folly
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