///////////////////////////////////////////////////////////////////////////////

// Copyright (c) Lewis Baker

// Licenced under MIT license. See LICENSE.txt for details.

///////////////////////////////////////////////////////////////////////////////

#include <cppcoro/multi_producer_sequencer.hpp>

#include <cppcoro/config.hpp>

#include <cppcoro/sequence_barrier.hpp>

#include <cppcoro/sequence_traits.hpp>

#include <cppcoro/on_scope_exit.hpp>

#include <cppcoro/sync_wait.hpp>

#include <cppcoro/when_all.hpp>

#include <cppcoro/task.hpp>

#include <cppcoro/static_thread_pool.hpp>

#include <thread>

#include <chrono>

#include <ostream>

#include "doctest/cppcoro_doctest.h"

DOCTEST_TEST_SUITE_BEGIN("multi_producer_sequencer");

using namespace cppcoro;

namespace

{

task<> one_at_a_time_producer(

static_thread_pool& tp,

multi_producer_sequencer<std::size_t>& sequencer,

std::uint64_t buffer[],

std::uint64_t iterationCount)

{

if (iterationCount == 0) co_return;

co_await tp.schedule();

const std::size_t bufferSize = sequencer.buffer_size();

const std::size_t mask = bufferSize - 1;

std::uint64_t i = 0;

while (i < iterationCount)

{

auto seq = co_await sequencer.claim_one(tp);

buffer[seq & mask] = ++i;

sequencer.publish(seq);

}

auto finalSeq = co_await sequencer.claim_one(tp);

buffer[finalSeq & mask] = 0;

sequencer.publish(finalSeq);

}

task<> batch_producer(

static_thread_pool& tp,

multi_producer_sequencer<std::size_t>& sequencer,

std::uint64_t buffer[],

std::uint64_t iterationCount,

std::size_t maxBatchSize)

{

const std::size_t bufferSize = sequencer.buffer_size();

std::uint64_t i = 0;

while (i < iterationCount)

{

const std::size_t batchSize = static_cast<std::size_t>(

std::min<std::uint64_t>(maxBatchSize, iterationCount - i));

auto sequences = co_await sequencer.claim_up_to(batchSize, tp);

for (auto seq : sequences)

{

buffer[seq % bufferSize] = ++i;

}

sequencer.publish(sequences);

}

auto finalSeq = co_await sequencer.claim_one(tp);

buffer[finalSeq % bufferSize] = 0;

sequencer.publish(finalSeq);

}

task<std::uint64_t> consumer(

static_thread_pool& tp,

const multi_producer_sequencer<std::size_t>& sequencer,

sequence_barrier<std::size_t>& readBarrier,

const std::uint64_t buffer[],

std::uint32_t producerCount)

{

co_await tp.schedule();

const std::size_t mask = sequencer.buffer_size() - 1;

std::uint64_t sum = 0;

std::uint32_t endCount = 0;

std::size_t nextToRead = 0;

do

{

std::size_t available = co_await sequencer.wait_until_published(nextToRead, nextToRead - 1, tp);

do

{

const auto& value = buffer[nextToRead & mask];

sum += value;

// Zero value is sentinel that indicates the end of one of the streams.

const bool isEndOfStream = value == 0;

endCount += isEndOfStream ? 1 : 0;

} while (nextToRead++ != available);

// Notify that we've finished processing up to 'available'.

readBarrier.publish(available);

} while (endCount < producerCount);

co_return sum;

}

}

DOCTEST_TEST_CASE("two producers (batch) / single consumer")

{

static_thread_pool tp{ 3 };

// Allow time for threads to start up.

using namespace std::chrono_literals;

std::this_thread::sleep_for(1ms);

constexpr std::size_t batchSize = 10;

constexpr std::size_t bufferSize = 16384;

sequence_barrier<std::size_t> readBarrier;

multi_producer_sequencer<std::size_t> sequencer(readBarrier, bufferSize);

constexpr std::uint64_t iterationCount = 1'000'000;

std::uint64_t buffer[bufferSize];

auto startTime = std::chrono::high_resolution_clock::now();

constexpr std::uint32_t producerCount = 2;

auto result = std::get<0>(sync_wait(when_all(

consumer(tp, sequencer, readBarrier, buffer, producerCount),

batch_producer(tp, sequencer, buffer, iterationCount, batchSize),

batch_producer(tp, sequencer, buffer, iterationCount, batchSize))));

auto endTime = std::chrono::high_resolution_clock::now();

auto totalTimeInNs = std::chrono::duration_cast<std::chrono::nanoseconds>(endTime - startTime).count();

MESSAGE(

"Producers = " << producerCount

<< ", BatchSize = " << batchSize

<< ", MessagesPerProducer = " << iterationCount

<< ", TotalTime = " << totalTimeInNs/1000 << "us"

<< ", TimePerMessage = " << totalTimeInNs/double(iterationCount * producerCount) << "ns"

<< ", MessagesPerSecond = " << 1'000'000'000 * (producerCount * iterationCount) / totalTimeInNs);

constexpr std::uint64_t expectedResult =

producerCount * std::uint64_t(iterationCount) * std::uint64_t(iterationCount + 1) / 2;

CHECK(result == expectedResult);

}

DOCTEST_TEST_CASE("two producers (single) / single consumer")

{

static_thread_pool tp{ 3 };

// Allow time for threads to start up.

using namespace std::chrono_literals;

std::this_thread::sleep_for(1ms);

constexpr std::size_t bufferSize = 16384;

sequence_barrier<std::size_t> readBarrier;

multi_producer_sequencer<std::size_t> sequencer(readBarrier, bufferSize);

constexpr std::uint64_t iterationCount = 1'000'000;

std::uint64_t buffer[bufferSize];

auto startTime = std::chrono::high_resolution_clock::now();

constexpr std::uint32_t producerCount = 2;

auto result = std::get<0>(sync_wait(when_all(

consumer(tp, sequencer, readBarrier, buffer, producerCount),

one_at_a_time_producer(tp, sequencer, buffer, iterationCount),

one_at_a_time_producer(tp, sequencer, buffer, iterationCount))));

auto endTime = std::chrono::high_resolution_clock::now();

auto totalTimeInNs = std::chrono::duration_cast<std::chrono::nanoseconds>(endTime - startTime).count();

MESSAGE(

"Producers = " << producerCount

<< ", NoBatch"

<< ", MessagesPerProducer = " << iterationCount

<< ", TotalTime = " << totalTimeInNs / 1000 << "us"

<< ", TimePerMessage = " << totalTimeInNs / double(iterationCount * producerCount) << "ns"

<< ", MessagesPerSecond = " << 1'000'000'000 * (producerCount * iterationCount) / totalTimeInNs);

constexpr std::uint64_t expectedResult =

producerCount * std::uint64_t(iterationCount) * std::uint64_t(iterationCount + 1) / 2;

CHECK(result == expectedResult);

}

DOCTEST_TEST_SUITE_END();