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Threading: Moving connectivity search to std::async 

By decoupling from std::thread, we can avoid the wait/sleep cycle in
checking the std::atomic completion variable.  The std::future variables
are immediately returning without the additional atomic check cycle.
This commit is contained in:
Seth Hillbrand 2018-10-26 18:00:43 -07:00
parent 4f11dc54fa
commit 59fb6d8851
1 changed files with 20 additions and 14 deletions
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34
pcbnew/connectivity/connectivity_algo.cpp
View File

@ -28,6 +28,8 @@
#include <thread>
#include <mutex>
#include <algorithm>
#include <future>
#ifdef PROFILE
#include <profile.h>
@ -218,11 +220,14 @@ void CN_CONNECTIVITY_ALGO::searchConnections()
if( m_itemList.IsDirty() )
{
std::atomic<size_t> nextItem( 0 );
std::atomic<size_t> threadsFinished( 0 );
size_t parallelThreadCount = std::min<size_t>( std::thread::hardware_concurrency(),
( dirtyItems.size() + 7 ) / 8 );
auto conn_lambda = [&nextItem, &threadsFinished, &dirtyItems]
( CN_LIST* aItemList, PROGRESS_REPORTER* aReporter)
std::atomic<size_t> nextItem( 0 );
std::vector<std::future<size_t>> returns( parallelThreadCount );
auto conn_lambda = [&nextItem, &dirtyItems]
( CN_LIST* aItemList, PROGRESS_REPORTER* aReporter) -> size_t
{
for( size_t i = nextItem++; i < dirtyItems.size(); i = nextItem++ )
{
@ -233,26 +238,27 @@ void CN_CONNECTIVITY_ALGO::searchConnections()
aReporter->AdvanceProgress();
}
threadsFinished++;
return 1;
};
size_t parallelThreadCount = std::min<size_t>( std::thread::hardware_concurrency(),
( dirtyItems.size() + 7 ) / 8 );
if( parallelThreadCount <= 1 )
conn_lambda( &m_itemList, m_progressReporter );
else
{
for( size_t ii = 0; ii < parallelThreadCount; ++ii )
std::thread( conn_lambda, &m_itemList, m_progressReporter ).detach();
returns[ii] = std::async( conn_lambda, &m_itemList, m_progressReporter );
// Wait for connectivity threads to finish while updating the UI if set
while( threadsFinished < parallelThreadCount )
for( size_t ii = 0; ii < parallelThreadCount; ++ii )
{
if( m_progressReporter )
m_progressReporter->KeepRefreshing();
// Here we balance returns with a 10ms timeout to allow UI updating
std::future_status status;
do
{
if( m_progressReporter )
m_progressReporter->KeepRefreshing();
std::this_thread::sleep_for( std::chrono::milliseconds( 1 ) );
status = returns[ii].wait_for( std::chrono::milliseconds( 10 ) );
} while( status != std::future_status::ready );
}
}