priority_thread_pool_task.h

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/*
 * This program source code file is part of KiCad, a free EDA CAD application.
 *
 * Copyright The KiCad Developers, see AUTHORS.txt for contributors.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, you may find one here:
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 * or you may search the http://www.gnu.org website for the version 2 license,
 * or you may write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 */
 
#pragma once
 
#include <thread_pool.h>
 

template <typename ContainerT>
class PRIORITY_THREAD_POOL_TASK
{
public:
    using ItemT = typename ContainerT::value_type;
 
    PRIORITY_THREAD_POOL_TASK() :
            m_reporter( nullptr ),
            m_highestPriority( BS::pr::high ),
            m_reporterInterval( std::chrono::milliseconds( 250 ) )
    {
    }
 
    void SetReporter( PROGRESS_REPORTER* aReporter ) { m_reporter = aReporter; }

    void Execute( ContainerT& aItems )
    {
        thread_pool&                     tp = GetKiCadThreadPool();
        std::vector<std::future<size_t>> returns;
 
        // Compute priority keys paired to item indices
        using IndexedPriority = std::pair<size_t, int>;
        std::vector<IndexedPriority> indexedKeys( aItems.size() );
        for( size_t i = 0; i < aItems.size(); ++i )
        {
            indexedKeys[i] = { i, computePriorityKey( aItems[i] ) };
        }
 
        // Sort by descending priority key
        std::sort( indexedKeys.begin(), indexedKeys.end(),
                   []( const IndexedPriority& a, const IndexedPriority& b )
                   {
                       return a.second > b.second;
                   } );
 
        // Dispatch largest first
        const size_t numItems = aItems.size();
        for( size_t priorityRank = 0; priorityRank < numItems; ++priorityRank )
        {
            const size_t itemIndex = indexedKeys[priorityRank].first;
            ItemT&       item = aItems[itemIndex];
 
            // Earlier ranking -> higher key -> should be higher priority
            const size_t priority = ( ( numItems - priorityRank - 1 ) * m_highestPriority ) / numItems;
 
            returns.emplace_back( tp.submit_task(
                    [this, &item]
                    {
                        return task( item );
                    },
                    priority ) );
        }
 
        for( const std::future<size_t>& ret : returns )
        {
            std::future_status status = ret.wait_for( m_reporterInterval );
 
            while( status != std::future_status::ready )
            {
                if( m_reporter )
                    m_reporter->KeepRefreshing();
 
                status = ret.wait_for( m_reporterInterval );
            }
        }
    }
 
protected:
    PROGRESS_REPORTER* m_reporter;
 
private:
    virtual int computePriorityKey( const ItemT& aItem ) const = 0;

    virtual size_t task( ItemT& item ) = 0;
 
    BS::priority_t            m_highestPriority;
    std::chrono::milliseconds m_reporterInterval;
};