reverse.hpp

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/*
Copyright (c) 2015, Scott Zuyderduyn
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//----------------------------------------------------------------------------
// algo/reverse.hpp
//
// Extension of std::reverse that recognizes device memory and can be called
// from host or device code.
//
// Author: Scott D. Zuyderduyn, Ph.D. (scott.zuyderduyn@utoronto.ca)
//----------------------------------------------------------------------------
#pragma once
#ifndef ECUDA_ALGO_REVERSE_HPP
#define ECUDA_ALGO_REVERSE_HPP

#include <iterator>
#include <vector>

#include "../global.hpp"
#include "../iterator.hpp"
//#include "../utility.hpp"
#include "../algorithm.hpp"

namespace ecuda {

// forward declaration
template<class BidirectionalIterator> __HOST__ __DEVICE__ inline void reverse( BidirectionalIterator first, BidirectionalIterator last );

namespace impl {

template<class ForwardIterator>
__HOST__ __DEVICE__ inline void
reverse( ForwardIterator first, ForwardIterator last,
         ecuda::false_type // host memory
)
{
    #ifdef __CUDA_ARCH__
    // never called from device code
    #else
    std::reverse( first, last );
    #endif
}

template<class ForwardIterator>
__HOST__ __DEVICE__ inline void
reverse( ForwardIterator first, ForwardIterator last,
         ecuda::true_type // device memory
)
{
    #ifdef __CUDA_ARCH__
    while( (first!=last) and (first!=--last) ) {
        ecuda::swap( *first, *last );
        ++first;
    }
    #else
    {
        typedef typename ecuda::iterator_traits<ForwardIterator>::iterator_category iterator_category;
        typedef typename ecuda::iterator_traits<ForwardIterator>::is_contiguous iterator_contiguity;
        const bool isSomeKindOfContiguous =
            ecuda::is_same<iterator_contiguity,ecuda::true_type>::value ||
            ecuda::is_same<iterator_category,device_contiguous_block_iterator_tag>::value;
        ECUDA_STATIC_ASSERT(isSomeKindOfContiguous,CANNOT_REVERSE_RANGE_REPRESENTED_BY_NONCONTIGUOUS_DEVICE_MEMORY);
    }
    typedef typename ecuda::remove_const<typename ecuda::iterator_traits<ForwardIterator>::value_type>::type value_type;
    std::vector< value_type, host_allocator<value_type> > v( ::ecuda::distance( first, last ) );
    ::ecuda::copy( first, last, v.begin() );
    ::ecuda::reverse( v.begin(), v.end() );
    ::ecuda::copy( v.begin(), v.end(), first );
    #endif
}

} // namespace impl

ECUDA_SUPPRESS_HD_WARNINGS
template<class BidirectionalIterator>
__HOST__ __DEVICE__ inline void reverse( BidirectionalIterator first, BidirectionalIterator last ) {
    impl::reverse(
        first, last,
        typename ecuda::iterator_traits<BidirectionalIterator>::is_device_iterator()
    );
}

} // namespace ecuda

#endif