/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
- Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
#ifdef USE_MPI
#include <array>
+#include <map>
#include <cstddef>
#include <cstdlib>
#include <iostream>
#include "cluster.h"
#include "thread.h"
#include "tt.h"
+#include "timeman.h"
+namespace Stockfish {
namespace Cluster {
+// Total number of ranks and rank within the communicator
static int world_rank = MPI_PROC_NULL;
static int world_size = 0;
+// Signals between ranks exchange basic info using a dedicated communicator
+static MPI_Comm signalsComm = MPI_COMM_NULL;
static MPI_Request reqSignals = MPI_REQUEST_NULL;
static uint64_t signalsCallCounter = 0;
-enum Signals : int { SIG_NODES = 0, SIG_STOP = 1, SIG_TB = 2, SIG_NB = 3};
+// Signals are the number of nodes searched, stop, table base hits, transposition table saves
+enum Signals : int { SIG_NODES = 0, SIG_STOP = 1, SIG_TB = 2, SIG_TTS = 3, SIG_NB = 4};
static uint64_t signalsSend[SIG_NB] = {};
static uint64_t signalsRecv[SIG_NB] = {};
-
static uint64_t nodesSearchedOthers = 0;
static uint64_t tbHitsOthers = 0;
+static uint64_t TTsavesOthers = 0;
static uint64_t stopSignalsPosted = 0;
+// The UCI threads of each rank exchange use a dedicated communicator
static MPI_Comm InputComm = MPI_COMM_NULL;
-static MPI_Comm TTComm = MPI_COMM_NULL;
-static MPI_Comm MoveComm = MPI_COMM_NULL;
-static MPI_Comm signalsComm = MPI_COMM_NULL;
-
-static std::vector<KeyedTTEntry> TTBuff;
+// bestMove requires MoveInfo communicators and data types
+static MPI_Comm MoveComm = MPI_COMM_NULL;
static MPI_Datatype MIDatatype = MPI_DATATYPE_NULL;
+// TT entries are communicated with a dedicated communicator.
+// The receive buffer is used to gather information from all ranks.
+// THe TTCacheCounter tracks the number of local elements that are ready to be sent.
+static MPI_Comm TTComm = MPI_COMM_NULL;
+static std::array<std::vector<KeyedTTEntry>, 2> TTSendRecvBuffs;
+static std::array<MPI_Request, 2> reqsTTSendRecv = {MPI_REQUEST_NULL, MPI_REQUEST_NULL};
+static uint64_t sendRecvPosted = 0;
+static std::atomic<uint64_t> TTCacheCounter = {};
+
+/// Initialize MPI and associated data types. Note that the MPI library must be configured
+/// to support MPI_THREAD_MULTIPLE, since multiple threads access MPI simultaneously.
void init() {
int thread_support;
MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);
MPI_Comm_size(MPI_COMM_WORLD, &world_size);
- TTBuff.resize(TTSendBufferSize * world_size);
-
- const std::array<MPI_Aint, 4> MIdisps = {offsetof(MoveInfo, move),
+ const std::array<MPI_Aint, 5> MIdisps = {offsetof(MoveInfo, move),
+ offsetof(MoveInfo, ponder),
offsetof(MoveInfo, depth),
offsetof(MoveInfo, score),
offsetof(MoveInfo, rank)};
- MPI_Type_create_hindexed_block(4, 1, MIdisps.data(), MPI_INT, &MIDatatype);
+ MPI_Type_create_hindexed_block(5, 1, MIdisps.data(), MPI_INT, &MIDatatype);
MPI_Type_commit(&MIDatatype);
MPI_Comm_dup(MPI_COMM_WORLD, &InputComm);
MPI_Comm_dup(MPI_COMM_WORLD, &signalsComm);
}
+/// Finalize MPI and free the associated data types.
void finalize() {
-
- // free data tyes and communicators
MPI_Type_free(&MIDatatype);
MPI_Comm_free(&InputComm);
MPI_Finalize();
}
+/// Return the total number of ranks
int size() {
return world_size;
}
+/// Return the rank (index) of the process
int rank() {
return world_rank;
}
+/// The receive buffer depends on the number of MPI ranks and threads, resize as needed
+void ttSendRecvBuff_resize(size_t nThreads) {
+
+ for (int i : {0, 1})
+ {
+ TTSendRecvBuffs[i].resize(TTCacheSize * world_size * nThreads);
+ std::fill(TTSendRecvBuffs[i].begin(), TTSendRecvBuffs[i].end(), KeyedTTEntry());
+ }
+}
+/// As input is only received by the root (rank 0) of the cluster, this input must be relayed
+/// to the UCI threads of all ranks, in order to setup the position, etc. We do this with a
+/// dedicated getline implementation, where the root broadcasts to all other ranks the received
+/// information.
bool getline(std::istream& input, std::string& str) {
int size;
size = vec.size();
}
- // Some MPI implementations use busy-wait polling, while we need yielding
+ // Some MPI implementations use busy-wait polling, while we need yielding as otherwise
+ // the UCI thread on the non-root ranks would be consuming resources.
static MPI_Request reqInput = MPI_REQUEST_NULL;
MPI_Ibcast(&size, 1, MPI_INT, 0, InputComm, &reqInput);
if (is_root())
}
}
+ // Broadcast received string
if (!is_root())
vec.resize(size);
MPI_Bcast(vec.data(), size, MPI_CHAR, 0, InputComm);
return state;
}
+/// Sending part of the signal communication loop
void signals_send() {
signalsSend[SIG_NODES] = Threads.nodes_searched();
signalsSend[SIG_TB] = Threads.tb_hits();
+ signalsSend[SIG_TTS] = Threads.TT_saves();
signalsSend[SIG_STOP] = Threads.stop;
MPI_Iallreduce(signalsSend, signalsRecv, SIG_NB, MPI_UINT64_T,
MPI_SUM, signalsComm, &reqSignals);
++signalsCallCounter;
}
+/// Processing part of the signal communication loop.
+/// For some counters (e.g. nodes) we only keep their sum on the other nodes
+/// allowing to add local counters at any time for more fine grained process,
+/// which is useful to indicate progress during early iterations, and to have
+/// node counts that exactly match the non-MPI code in the single rank case.
+/// This call also propagates the stop signal between ranks.
void signals_process() {
nodesSearchedOthers = signalsRecv[SIG_NODES] - signalsSend[SIG_NODES];
tbHitsOthers = signalsRecv[SIG_TB] - signalsSend[SIG_TB];
+ TTsavesOthers = signalsRecv[SIG_TTS] - signalsSend[SIG_TTS];
stopSignalsPosted = signalsRecv[SIG_STOP];
if (signalsRecv[SIG_STOP] > 0)
Threads.stop = true;
}
+void sendrecv_post() {
+
+ ++sendRecvPosted;
+ MPI_Irecv(TTSendRecvBuffs[sendRecvPosted % 2].data(),
+ TTSendRecvBuffs[sendRecvPosted % 2].size() * sizeof(KeyedTTEntry), MPI_BYTE,
+ (rank() + size() - 1) % size(), 42, TTComm, &reqsTTSendRecv[0]);
+ MPI_Isend(TTSendRecvBuffs[(sendRecvPosted + 1) % 2].data(),
+ TTSendRecvBuffs[(sendRecvPosted + 1) % 2].size() * sizeof(KeyedTTEntry), MPI_BYTE,
+ (rank() + 1 ) % size(), 42, TTComm, &reqsTTSendRecv[1]);
+}
+
+/// During search, most message passing is asynchronous, but at the end of
+/// search it makes sense to bring them to a common, finalized state.
void signals_sync() {
while(stopSignalsPosted < uint64_t(size()))
signals_poll();
- // finalize outstanding messages of the signal loops. We might have issued one call less than needed on some ranks.
+ // Finalize outstanding messages of the signal loops.
+ // We might have issued one call less than needed on some ranks.
uint64_t globalCounter;
- MPI_Allreduce(&signalsCallCounter, &globalCounter, 1, MPI_UINT64_T, MPI_MAX, MoveComm); // MoveComm needed
+ MPI_Allreduce(&signalsCallCounter, &globalCounter, 1, MPI_UINT64_T, MPI_MAX, MoveComm);
if (signalsCallCounter < globalCounter)
+ {
+ MPI_Wait(&reqSignals, MPI_STATUS_IGNORE);
signals_send();
-
+ }
assert(signalsCallCounter == globalCounter);
-
MPI_Wait(&reqSignals, MPI_STATUS_IGNORE);
-
signals_process();
+ // Finalize outstanding messages in the sendRecv loop
+ MPI_Allreduce(&sendRecvPosted, &globalCounter, 1, MPI_UINT64_T, MPI_MAX, MoveComm);
+ while (sendRecvPosted < globalCounter)
+ {
+ MPI_Waitall(reqsTTSendRecv.size(), reqsTTSendRecv.data(), MPI_STATUSES_IGNORE);
+ sendrecv_post();
+ }
+ assert(sendRecvPosted == globalCounter);
+ MPI_Waitall(reqsTTSendRecv.size(), reqsTTSendRecv.data(), MPI_STATUSES_IGNORE);
+
}
+/// Initialize signal counters to zero.
void signals_init() {
- stopSignalsPosted = tbHitsOthers = nodesSearchedOthers = 0;
+ stopSignalsPosted = tbHitsOthers = TTsavesOthers = nodesSearchedOthers = 0;
signalsSend[SIG_NODES] = signalsRecv[SIG_NODES] = 0;
signalsSend[SIG_TB] = signalsRecv[SIG_TB] = 0;
+ signalsSend[SIG_TTS] = signalsRecv[SIG_TTS] = 0;
signalsSend[SIG_STOP] = signalsRecv[SIG_STOP] = 0;
}
+/// Poll the signal loop, and start next round as needed.
void signals_poll() {
int flag;
}
}
+/// Provide basic info related the cluster performance, in particular, the number of signals send,
+/// signals per sounds (sps), the number of gathers, the number of positions gathered (per node and per second, gpps)
+/// The number of TT saves and TT saves per second. If gpps equals approximately TTSavesps the gather loop has enough bandwidth.
+void cluster_info(Depth depth) {
+
+ TimePoint elapsed = Time.elapsed() + 1;
+ uint64_t TTSaves = TT_saves();
+
+ sync_cout << "info depth " << depth << " cluster "
+ << " signals " << signalsCallCounter << " sps " << signalsCallCounter * 1000 / elapsed
+ << " sendRecvs " << sendRecvPosted << " srpps " << TTSendRecvBuffs[0].size() * sendRecvPosted * 1000 / elapsed
+ << " TTSaves " << TTSaves << " TTSavesps " << TTSaves * 1000 / elapsed
+ << sync_endl;
+}
+
+/// When a TT entry is saved, additional steps are taken if the entry is of sufficient depth.
+/// If sufficient entries has been collected, a communication is initiated.
+/// If a communication has been completed, the received results are saved to the TT.
void save(Thread* thread, TTEntry* tte,
- Key k, Value v, Bound b, Depth d, Move m, Value ev) {
+ Key k, Value v, bool PvHit, Bound b, Depth d, Move m, Value ev) {
- tte->save(k, v, b, d, m, ev);
+ // Standard save to the TT
+ tte->save(k, v, PvHit, b, d, m, ev);
- if (d > 5 * ONE_PLY)
+ // If the entry is of sufficient depth to be worth communicating, take action.
+ if (d > 3)
{
- // Try to add to thread's send buffer
+ // count the TTsaves to information: this should be relatively similar
+ // to the number of entries we can send/recv.
+ thread->TTsaves.fetch_add(1, std::memory_order_relaxed);
+
+ // Add to thread's send buffer, the locking here avoids races when the master thread
+ // prepares the send buffer.
{
- std::lock_guard<Mutex> lk(thread->ttBuffer.mutex);
- thread->ttBuffer.buffer.replace(KeyedTTEntry(k,*tte));
- ++thread->ttBuffer.counter;
+ std::lock_guard<std::mutex> lk(thread->ttCache.mutex);
+ thread->ttCache.buffer.replace(KeyedTTEntry(k,*tte));
+ ++TTCacheCounter;
}
- // Communicate on main search thread
- if (thread == Threads.main() && thread->ttBuffer.counter * Threads.size() > TTSendBufferSize)
- {
- static MPI_Request req = MPI_REQUEST_NULL;
- static TTSendBuffer<TTSendBufferSize> send_buff = {};
- int flag;
+ size_t recvBuffPerRankSize = Threads.size() * TTCacheSize;
+ // Communicate on main search thread, as soon the threads combined have collected
+ // sufficient data to fill the send buffers.
+ if (thread == Threads.main() && TTCacheCounter > recvBuffPerRankSize)
+ {
// Test communication status
- MPI_Test(&req, &flag, MPI_STATUS_IGNORE);
+ int flag;
+ MPI_Testall(reqsTTSendRecv.size(), reqsTTSendRecv.data(), &flag, MPI_STATUSES_IGNORE);
// Current communication is complete
if (flag)
{
- // Save all received entries (except ours)
+ // Save all received entries to TT, and store our TTCaches, ready for the next round of communication
for (size_t irank = 0; irank < size_t(size()) ; ++irank)
{
- if (irank == size_t(rank()))
- continue;
-
- for (size_t i = irank * TTSendBufferSize ; i < (irank + 1) * TTSendBufferSize; ++i)
+ if (irank == size_t(rank())) // this is our part, fill the part of the buffer for sending
{
- auto&& e = TTBuff[i];
- bool found;
- TTEntry* replace_tte;
- replace_tte = TT.probe(e.first, found);
- replace_tte->save(e.first, e.second.value(), e.second.bound(), e.second.depth(),
- e.second.move(), e.second.eval());
- }
- }
+ // Copy from the thread caches to the right spot in the buffer
+ size_t i = irank * recvBuffPerRankSize;
+ for (auto&& th : Threads)
+ {
+ std::lock_guard<std::mutex> lk(th->ttCache.mutex);
- // Reset send buffer
- send_buff = {};
+ for (auto&& e : th->ttCache.buffer)
+ TTSendRecvBuffs[sendRecvPosted % 2][i++] = e;
- // Build up new send buffer: best 16 found across all threads
- for (auto&& th : Threads)
- {
- std::lock_guard<Mutex> lk(th->ttBuffer.mutex);
- for (auto&& e : th->ttBuffer.buffer)
- send_buff.replace(e);
- // Reset thread's send buffer
- th->ttBuffer.buffer = {};
- th->ttBuffer.counter = 0;
+ // Reset thread's send buffer
+ th->ttCache.buffer = {};
+ }
+
+ TTCacheCounter = 0;
+ }
+ else // process data received from the corresponding rank.
+ for (size_t i = irank * recvBuffPerRankSize; i < (irank + 1) * recvBuffPerRankSize; ++i)
+ {
+ auto&& e = TTSendRecvBuffs[sendRecvPosted % 2][i];
+ bool found;
+ TTEntry* replace_tte;
+ replace_tte = TT.probe(e.first, found);
+ replace_tte->save(e.first, e.second.value(), e.second.is_pv(), e.second.bound(), e.second.depth(),
+ e.second.move(), e.second.eval());
+ }
}
// Start next communication
- MPI_Iallgather(send_buff.data(), send_buff.size() * sizeof(KeyedTTEntry), MPI_BYTE,
- TTBuff.data(), TTSendBufferSize * sizeof(KeyedTTEntry), MPI_BYTE,
- TTComm, &req);
+ sendrecv_post();
+
+ // Force check of time on the next occasion, the above actions might have taken some time.
+ static_cast<MainThread*>(thread)->callsCnt = 0;
+
}
}
}
}
-
-// TODO update to the scheme in master.. can this use aggregation of votes?
-void pick_moves(MoveInfo& mi) {
+/// Picks the bestMove across ranks, and send the associated info and PV to the root of the cluster.
+/// Note that this bestMove and PV must be output by the root, the guarantee proper ordering of output.
+/// TODO update to the scheme in master.. can this use aggregation of votes?
+void pick_moves(MoveInfo& mi, std::string& PVLine) {
MoveInfo* pMoveInfo = NULL;
if (is_root())
}
free(pMoveInfo);
}
+
+ // Send around the final result
MPI_Bcast(&mi, 1, MIDatatype, 0, MoveComm);
+
+ // Send PV line to root as needed
+ if (mi.rank != 0 && mi.rank == rank()) {
+ int size;
+ std::vector<char> vec;
+ vec.assign(PVLine.begin(), PVLine.end());
+ size = vec.size();
+ MPI_Send(&size, 1, MPI_INT, 0, 42, MoveComm);
+ MPI_Send(vec.data(), size, MPI_CHAR, 0, 42, MoveComm);
+ }
+ if (mi.rank != 0 && is_root()) {
+ int size;
+ std::vector<char> vec;
+ MPI_Recv(&size, 1, MPI_INT, mi.rank, 42, MoveComm, MPI_STATUS_IGNORE);
+ vec.resize(size);
+ MPI_Recv(vec.data(), size, MPI_CHAR, mi.rank, 42, MoveComm, MPI_STATUS_IGNORE);
+ PVLine.assign(vec.begin(), vec.end());
+ }
+
}
+/// Return nodes searched (lazily updated cluster wide in the signal loop)
uint64_t nodes_searched() {
return nodesSearchedOthers + Threads.nodes_searched();
}
+/// Return table base hits (lazily updated cluster wide in the signal loop)
uint64_t tb_hits() {
return tbHitsOthers + Threads.tb_hits();
}
+/// Return the number of saves to the TT buffers, (lazily updated cluster wide in the signal loop)
+uint64_t TT_saves() {
+
+ return TTsavesOthers + Threads.TT_saves();
+}
+
+
+}
}
#else
#include "cluster.h"
#include "thread.h"
+namespace Stockfish {
namespace Cluster {
uint64_t nodes_searched() {
return Threads.tb_hits();
}
+uint64_t TT_saves() {
+
+ return Threads.TT_saves();
+}
+
+}
}
#endif // USE_MPI
projects / stockfish / blobdiff