count_if.hpp

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/*
Copyright (c) 2015, Scott Zuyderduyn
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//----------------------------------------------------------------------------
// algo/count_if.hpp
//
// Extension of std::count_if 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_COUNT_IF_HPP
#define ECUDA_ALGO_COUNT_IF_HPP

#include <algorithm>
#include <vector>

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

namespace ecuda {

namespace impl {

template<class InputIterator,class UnaryPredicate>
inline __HOST__ __DEVICE__ typename ecuda::iterator_traits<InputIterator>::difference_type
count_if( InputIterator first, InputIterator last, UnaryPredicate p, ecuda::false_type ) // host memory
{
    #ifdef __CUDA_ARCH__
    return 0; // never called from device code
    #else
    // just defer to STL
    return std::count_if( first, last, p );
    #endif
}

template<class InputIterator,class UnaryPredicate>
__HOST__ __DEVICE__ typename ecuda::iterator_traits<InputIterator>::difference_type
count_if( InputIterator first, InputIterator last, UnaryPredicate p, ecuda::true_type ) // device memory
{
    #ifdef __CUDA_ARCH__
    typename ecuda::iterator_traits<InputIterator>::difference_type n = 0;
    while( first != last ) {
        if( p(*first) ) ++n;
        ++first;
    }
    return n;
    #else
    typedef typename ecuda::remove_const<typename ecuda::iterator_traits<InputIterator>::value_type>::type value_type;
    std::vector< value_type, host_allocator<value_type> > v( ecuda::distance(first,last) );
    ecuda::copy( first, last, v.begin() );
    return std::count_if( v.begin(), v.end(), p );
    #endif
}

} // namespace impl

ECUDA_SUPPRESS_HD_WARNINGS
template<class InputIterator,class UnaryPredicate>
inline __HOST__ __DEVICE__ typename ecuda::iterator_traits<InputIterator>::difference_type
count_if( InputIterator first, InputIterator last, UnaryPredicate p )
{
    return impl::count_if( first, last, p, typename ecuda::iterator_traits<InputIterator>::is_device_iterator() );
}

} // namespace ecuda

#endif