/***************************************************************************
                          MemoryOperationsHost.hpp  -  description
                             -------------------
    begin                : Jul 16, 2013
    copyright            : (C) 2013 by Tomas Oberhuber
    email                : tomas.oberhuber@fjfi.cvut.cz
 ***************************************************************************/

/* See Copyright Notice in tnl/Copyright */

#pragma once

#include <type_traits>
#include <stdexcept>
#include <algorithm>  // std::copy, std::equal

#include <TNL/Algorithms/MemoryOperations.h>
#include <TNL/Algorithms/ParallelFor.h>
#include <TNL/Algorithms/Reduction.h>

namespace TNL {
namespace Algorithms {

template< typename Element >
void
MemoryOperations< Devices::Host >::
setElement( Element* data,
            const Element& value )
{
   TNL_ASSERT_TRUE( data, "Attempted to set data through a nullptr." );
   *data = value;
}

template< typename Element >
Element
MemoryOperations< Devices::Host >::
getElement( const Element* data )
{
   TNL_ASSERT_TRUE( data, "Attempted to get data through a nullptr." );
   return *data;
}

template< typename Element, typename Index >
void
MemoryOperations< Devices::Host >::
set( Element* data,
     const Element& value,
     const Index size )
{
   if( size == 0 ) return;
   TNL_ASSERT_TRUE( data, "Attempted to set data through a nullptr." );
   auto kernel = [data, value]( Index i )
   {
      data[ i ] = value;
   };
   ParallelFor< Devices::Host >::exec( (Index) 0, size, kernel );
}

template< typename DestinationElement,
          typename SourceElement,
          typename Index >
void
MemoryOperations< Devices::Host >::
copy( DestinationElement* destination,
      const SourceElement* source,
      const Index size )
{
   if( size == 0 ) return;
   TNL_ASSERT_TRUE( destination, "Attempted to copy data to a nullptr." );
   TNL_ASSERT_TRUE( source, "Attempted to copy data from a nullptr." );

   // our ParallelFor version is faster than std::copy iff we use more than 1 thread
   if( Devices::Host::isOMPEnabled() && Devices::Host::getMaxThreadsCount() > 1 ) {
      auto kernel = [destination, source]( Index i )
      {
         destination[ i ] = source[ i ];
      };
      ParallelFor< Devices::Host >::exec( (Index) 0, size, kernel );
   }
   else {
      // std::copy usually uses std::memcpy for TriviallyCopyable types
      std::copy( source, source + size, destination );
   }
}

template< typename DestinationElement,
          typename Index,
          typename SourceIterator >
void
MemoryOperations< Devices::Host >::
copyFromIterator( DestinationElement* destination,
                  Index destinationSize,
                  SourceIterator first,
                  SourceIterator last )
{
   MemoryOperations< Devices::Sequential >::copyFromIterator( destination, destinationSize, first, last );
}

template< typename DestinationElement,
          typename SourceElement,
          typename Index >
bool
MemoryOperations< Devices::Host >::
compare( const DestinationElement* destination,
         const SourceElement* source,
         const Index size )
{
   if( size == 0 ) return true;
   TNL_ASSERT_TRUE( destination, "Attempted to compare data through a nullptr." );
   TNL_ASSERT_TRUE( source, "Attempted to compare data through a nullptr." );

   if( Devices::Host::isOMPEnabled() && Devices::Host::getMaxThreadsCount() > 1 ) {
      auto fetch = [destination, source] ( Index i ) -> bool { return destination[ i ] == source[ i ]; };
      return Reduction< Devices::Host >::reduce( size, std::logical_and<>{}, fetch, true );
   }
   else {
      // sequential algorithm can return as soon as it finds a mismatch
      return std::equal( source, source + size, destination );
   }
}

template< typename Element,
          typename Index >
bool
MemoryOperations< Devices::Host >::
containsValue( const Element* data,
               const Index size,
               const Element& value )
{
   if( size == 0 ) return false;
   TNL_ASSERT_TRUE( data, "Attempted to check data through a nullptr." );
   TNL_ASSERT_GE( size, 0, "" );

   if( Devices::Host::isOMPEnabled() && Devices::Host::getMaxThreadsCount() > 1 ) {
      auto fetch = [=] ( Index i ) -> bool { return data[ i ] == value; };
      return Reduction< Devices::Host >::reduce( size, std::logical_or<>{}, fetch, false );
   }
   else {
      // sequential algorithm can return as soon as it finds a match
      return MemoryOperations< Devices::Sequential >::containsValue( data, size, value );
   }
}

template< typename Element,
          typename Index >
bool
MemoryOperations< Devices::Host >::
containsOnlyValue( const Element* data,
                   const Index size,
                   const Element& value )
{
   if( size == 0 ) return false;
   TNL_ASSERT_TRUE( data, "Attempted to check data through a nullptr." );
   TNL_ASSERT_GE( size, 0, "" );

   if( Devices::Host::isOMPEnabled() && Devices::Host::getMaxThreadsCount() > 1 ) {
      auto fetch = [data, value] ( Index i ) -> bool { return data[ i ] == value; };
      return Reduction< Devices::Host >::reduce( size, std::logical_and<>{}, fetch, true );
   }
   else {
      // sequential algorithm can return as soon as it finds a mismatch
      return MemoryOperations< Devices::Sequential >::containsOnlyValue( data, size, value );
   }
}

} // namespace Algorithms
} // namespace TNL
