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//===-- LatencyBenchmarkRunner.cpp ------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "LatencyBenchmarkRunner.h"
#include "BenchmarkRunner.h"
#include "Target.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/Error.h"
#include <algorithm>
#include <cmath>
#define DEBUG_TYPE "exegesis-latency-benchmarkrunner"
namespace llvm {
namespace exegesis {
LatencyBenchmarkRunner::LatencyBenchmarkRunner(
const LLVMState &State, Benchmark::ModeE Mode,
BenchmarkPhaseSelectorE BenchmarkPhaseSelector,
Benchmark::ResultAggregationModeE ResultAgg, ExecutionModeE ExecutionMode,
ArrayRef<ValidationEvent> ValCounters, unsigned BenchmarkRepeatCount)
: BenchmarkRunner(State, Mode, BenchmarkPhaseSelector, ExecutionMode,
ValCounters) {
assert((Mode == Benchmark::Latency || Mode == Benchmark::InverseThroughput) &&
"invalid mode");
ResultAggMode = ResultAgg;
NumMeasurements = BenchmarkRepeatCount;
}
LatencyBenchmarkRunner::~LatencyBenchmarkRunner() = default;
static double computeVariance(const SmallVector<int64_t, 4> &Values) {
if (Values.empty())
return 0.0;
double Sum = std::accumulate(Values.begin(), Values.end(), 0.0);
const double Mean = Sum / Values.size();
double Ret = 0;
for (const auto &V : Values) {
double Delta = V - Mean;
Ret += Delta * Delta;
}
return Ret / Values.size();
}
static int64_t findMin(const SmallVector<int64_t, 4> &Values) {
if (Values.empty())
return 0;
return *llvm::min_element(Values);
}
static int64_t findMax(const SmallVector<int64_t, 4> &Values) {
if (Values.empty())
return 0;
return *llvm::max_element(Values);
}
static int64_t findMean(const SmallVector<int64_t, 4> &Values) {
if (Values.empty())
return 0;
return std::accumulate(Values.begin(), Values.end(), 0.0) /
static_cast<double>(Values.size());
}
Expected<std::vector<BenchmarkMeasure>> LatencyBenchmarkRunner::runMeasurements(
const FunctionExecutor &Executor) const {
// Cycle measurements include some overhead from the kernel. Repeat the
// measure several times and return the aggregated value, as specified by
// ResultAggMode.
SmallVector<int64_t, 4> AccumulatedValues;
double MinVariance = std::numeric_limits<double>::infinity();
const PfmCountersInfo &PCI = State.getPfmCounters();
const char *CounterName = PCI.CycleCounter;
SmallVector<const char *> ValCountersToRun;
Error ValCounterErr = getValidationCountersToRun(ValCountersToRun);
if (ValCounterErr)
return std::move(ValCounterErr);
SmallVector<int64_t> ValCounterValues(ValCountersToRun.size(), 0);
// Values count for each run.
int ValuesCount = 0;
for (size_t I = 0; I < NumMeasurements; ++I) {
SmallVector<int64_t> IterationValCounterValues(ValCountersToRun.size(), -1);
auto ExpectedCounterValues = Executor.runAndSample(
CounterName, ValCountersToRun, IterationValCounterValues);
if (!ExpectedCounterValues)
return ExpectedCounterValues.takeError();
ValuesCount = ExpectedCounterValues.get().size();
if (ValuesCount == 1) {
LLVM_DEBUG(dbgs() << "Latency value: " << ExpectedCounterValues.get()[0]
<< "\n");
AccumulatedValues.push_back(ExpectedCounterValues.get()[0]);
} else {
// We'll keep the reading with lowest variance (ie., most stable)
double Variance = computeVariance(*ExpectedCounterValues);
if (MinVariance > Variance) {
AccumulatedValues = std::move(ExpectedCounterValues.get());
MinVariance = Variance;
}
}
for (size_t I = 0; I < ValCounterValues.size(); ++I) {
LLVM_DEBUG(dbgs() << getValidationEventName(ValidationCounters[I]) << ": "
<< IterationValCounterValues[I] << "\n");
ValCounterValues[I] += IterationValCounterValues[I];
}
}
std::map<ValidationEvent, int64_t> ValidationInfo;
for (size_t I = 0; I < ValidationCounters.size(); ++I)
ValidationInfo[ValidationCounters[I]] = ValCounterValues[I];
std::string ModeName;
switch (Mode) {
case Benchmark::Latency:
ModeName = "latency";
break;
case Benchmark::InverseThroughput:
ModeName = "inverse_throughput";
break;
default:
break;
}
switch (ResultAggMode) {
case Benchmark::MinVariance: {
if (ValuesCount == 1)
errs() << "Each sample only has one value. result-aggregation-mode "
"of min-variance is probably non-sensical\n";
std::vector<BenchmarkMeasure> Result;
Result.reserve(AccumulatedValues.size());
for (const int64_t Value : AccumulatedValues)
Result.push_back(
BenchmarkMeasure::Create(ModeName, Value, ValidationInfo));
return std::move(Result);
}
case Benchmark::Min: {
std::vector<BenchmarkMeasure> Result;
Result.push_back(BenchmarkMeasure::Create(
ModeName, findMin(AccumulatedValues), ValidationInfo));
return std::move(Result);
}
case Benchmark::Max: {
std::vector<BenchmarkMeasure> Result;
Result.push_back(BenchmarkMeasure::Create(
ModeName, findMax(AccumulatedValues), ValidationInfo));
return std::move(Result);
}
case Benchmark::Mean: {
std::vector<BenchmarkMeasure> Result;
Result.push_back(BenchmarkMeasure::Create(
ModeName, findMean(AccumulatedValues), ValidationInfo));
return std::move(Result);
}
}
return make_error<Failure>(Twine("Unexpected benchmark mode(")
.concat(std::to_string(Mode))
.concat(" and unexpected ResultAggMode ")
.concat(std::to_string(ResultAggMode)));
}
} // namespace exegesis
} // namespace llvm
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