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[cluster] keep track of node counts cluster-wide.

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This generalizes exchange of signals between the ranks using a non-blocking all-reduce. It is now used for the stop signal and the node count, but should be easily generalizable (TB hits, and ponder still missing). It avoids having long-lived outstanding non-blocking collectives (removes an early posted Ibarrier). A bit too short a test, but not worse than before:

Score of new-r4-1t vs old-r4-1t: 459 - 401 - 1505  [0.512] 2365
Elo difference: 8.52 +/- 8.43
This commit is contained in:
Joost VandeVondele
2018-12-29 15:34:57 +01:00
committed by Stéphane Nicolet
parent 2f882309d5
commit 87f0fa55a0
7 changed files with 123 additions and 65 deletions
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src/search.cpp
+13 -13
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@@ -234,14 +234,14 @@ void MainThread::search() {
Threads.stopOnPonderhit = true;
while (!Threads.stop && (Threads.ponder || Limits.infinite))
{ } // Busy wait for a stop or a ponder reset
{ Cluster::signals_poll(); } // Busy wait for a stop or a ponder reset
// Stop the threads if not already stopped (also raise the stop if
// "ponderhit" just reset Threads.ponder).
Threads.stop = true;
// Finish any outstanding barriers.
Cluster::sync_stop();
// Signal and synchronize all other ranks
Cluster::signals_sync();
// Wait until all threads have finished
for (Thread* th : Threads)
@@ -251,7 +251,7 @@ void MainThread::search() {
// When playing in 'nodes as time' mode, subtract the searched nodes from
// the available ones before exiting.
if (Limits.npmsec)
Time.availableNodes += Limits.inc[us] - Threads.nodes_searched();
Time.availableNodes += Limits.inc[us] - Cluster::nodes_searched();
// Check if there are threads with a better score than main thread
Thread* bestThread = this;
@@ -370,7 +370,7 @@ void Thread::search() {
// Iterative deepening loop until requested to stop or the target depth is reached
while ( (rootDepth += ONE_PLY) < DEPTH_MAX
&& !Threads.stop
&& !(Limits.depth && mainThread && rootDepth / ONE_PLY > Limits.depth))
&& !(Limits.depth && mainThread && Cluster::is_root() && rootDepth / ONE_PLY > Limits.depth))
{
// Distribute search depths across the helper threads
if (idx + Cluster::rank() > 0)
@@ -384,6 +384,7 @@ void Thread::search() {
if (mainThread)
mainThread->bestMoveChanges *= 0.517, failedLow = false;
// Save the last iteration's scores before first PV line is searched and
// all the move scores except the (new) PV are set to -VALUE_INFINITE.
for (RootMove& rm : rootMoves)
@@ -1609,16 +1610,16 @@ void MainThread::check_time() {
dbg_print();
}
// poll on MPI signals
Cluster::signals_poll();
// We should not stop pondering until told so by the GUI
if (Threads.ponder)
return;
// Check if root has reached a stop barrier
Cluster::sync_stop();
if ( (Limits.use_time_management() && elapsed > Time.maximum() - 10)
|| (Limits.movetime && elapsed >= Limits.movetime)
|| (Limits.nodes && Threads.nodes_searched() >= (uint64_t)Limits.nodes))
|| (Limits.nodes && Cluster::nodes_searched() >= (uint64_t)Limits.nodes))
Threads.stop = true;
}
@@ -1633,7 +1634,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
const RootMoves& rootMoves = pos.this_thread()->rootMoves;
size_t pvIdx = pos.this_thread()->pvIdx;
size_t multiPV = std::min((size_t)Options["MultiPV"], rootMoves.size());
uint64_t nodesSearched = Threads.nodes_searched();
uint64_t nodesSearched = Cluster::nodes_searched();
uint64_t tbHits = Threads.tb_hits() + (TB::RootInTB ? rootMoves.size() : 0);
for (size_t i = 0; i < multiPV; ++i)
@@ -1661,9 +1662,8 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
if (!tb && i == pvIdx)
ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : "");
// TODO fix approximate node calculation.
ss << " nodes " << nodesSearched * Cluster::size()
<< " nps " << nodesSearched * Cluster::size() * 1000 / elapsed;
ss << " nodes " << nodesSearched
<< " nps " << nodesSearched * 1000 / elapsed;
if (elapsed > 1000) // Earlier makes little sense
ss << " hashfull " << TT.hashfull();