concurrent_vector.h

/*
    Copyright 2005-2016 Intel Corporation.  All Rights Reserved.

    This file is part of Threading Building Blocks. Threading Building Blocks is free software;
    you can redistribute it and/or modify it under the terms of the GNU General Public License
    version 2  as  published  by  the  Free Software Foundation.  Threading Building Blocks 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 Threading Building Blocks; if not, write to the
    Free Software Foundation, Inc.,  51 Franklin St,  Fifth Floor,  Boston,  MA 02110-1301 USA

    As a special exception,  you may use this file  as part of a free software library without
    restriction.  Specifically,  if other files instantiate templates  or use macros or inline
    functions from this file, or you compile this file and link it with other files to produce
    an executable,  this file does not by itself cause the resulting executable to be covered
    by the GNU General Public License. This exception does not however invalidate any other
    reasons why the executable file might be covered by the GNU General Public License.
*/

#ifndef __TBB_concurrent_vector_H
#define __TBB_concurrent_vector_H

#include "tbb_stddef.h"
#include "tbb_exception.h"
#include "atomic.h"
#include "cache_aligned_allocator.h"
#include "blocked_range.h"
#include "tbb_machine.h"
#include "tbb_profiling.h"
#include <new>
#include <cstring>   // for memset()

#if !TBB_USE_EXCEPTIONS && _MSC_VER
    // Suppress "C++ exception handler used, but unwind semantics are not enabled" warning in STL headers
    #pragma warning (push)
    #pragma warning (disable: 4530)
#endif

#include <algorithm>
#include <iterator>

#if !TBB_USE_EXCEPTIONS && _MSC_VER
    #pragma warning (pop)
#endif

#if _MSC_VER==1500 && !__INTEL_COMPILER
    // VS2008/VC9 seems to have an issue; limits pull in math.h
    #pragma warning( push )
    #pragma warning( disable: 4985 )
#endif
#include <limits> /* std::numeric_limits */
#if _MSC_VER==1500 && !__INTEL_COMPILER
    #pragma warning( pop )
#endif

#if __TBB_INITIALIZER_LISTS_PRESENT
    #include <initializer_list>
#endif

#if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
    // Workaround for overzealous compiler warnings in /Wp64 mode
    #pragma warning (push)
#if defined(_Wp64)
    #pragma warning (disable: 4267)
#endif
    #pragma warning (disable: 4127) //warning C4127: conditional expression is constant
#endif

namespace tbb {

template<typename T, class A = cache_aligned_allocator<T> >
class concurrent_vector;

namespace internal {

    template<typename Container, typename Value>
    class vector_iterator;

    static void *const vector_allocation_error_flag = reinterpret_cast<void*>(size_t(63));

    template<typename T>
    void handle_unconstructed_elements(T* array, size_t n_of_elements){
        std::memset( array, 0, n_of_elements * sizeof( T ) );
    }


    class concurrent_vector_base_v3 {
    protected:

        // Basic types declarations
        typedef size_t segment_index_t;
        typedef size_t size_type;

        // Using enumerations due to Mac linking problems of static const variables
        enum {
            // Size constants
            default_initial_segments = 1, // 2 initial items
            pointers_per_short_table = 3, // to fit into 8 words of entire structure
            pointers_per_long_table = sizeof(segment_index_t) * 8 // one segment per bit
        };

        struct segment_not_used {};
        struct segment_allocated {};
        struct segment_allocation_failed {};

        class segment_t;
        class segment_value_t {
            void* array;
        private:
            //TODO: More elegant way to grant access to selected functions _only_?
            friend class segment_t;
            explicit segment_value_t(void* an_array):array(an_array) {}
        public:
            friend bool operator==(segment_value_t const& lhs, segment_not_used ) { return lhs.array == 0;}
            friend bool operator==(segment_value_t const& lhs, segment_allocated) { return lhs.array > internal::vector_allocation_error_flag;}
            friend bool operator==(segment_value_t const& lhs, segment_allocation_failed) { return lhs.array == internal::vector_allocation_error_flag;}
            template<typename argument_type>
            friend bool operator!=(segment_value_t const& lhs, argument_type arg) { return ! (lhs == arg);}

            template<typename T>
            T* pointer() const {  return static_cast<T*>(const_cast<void*>(array)); }
        };

        friend void enforce_segment_allocated(segment_value_t const& s, internal::exception_id exception = eid_bad_last_alloc){
            if(s != segment_allocated()){
                internal::throw_exception(exception);
            }
        }

        // Segment pointer.
        class segment_t {
            atomic<void*> array;
        public:
            segment_t(){ store<relaxed>(segment_not_used());}
            //Copy ctor and assignment operator are defined to ease using of stl algorithms.
            //These algorithms usually not a synchronization point, so, semantic is
            //intentionally relaxed here.
            segment_t(segment_t const& rhs ){ array.store<relaxed>(rhs.array.load<relaxed>());}

            void swap(segment_t & rhs ){
                tbb::internal::swap<relaxed>(array, rhs.array);
            }

            segment_t& operator=(segment_t const& rhs ){
                array.store<relaxed>(rhs.array.load<relaxed>());
                return *this;
            }

            template<memory_semantics M>
            segment_value_t load() const { return segment_value_t(array.load<M>());}

            template<memory_semantics M>
            void store(segment_not_used) {
                array.store<M>(0);
            }

            template<memory_semantics M>
            void store(segment_allocation_failed) {
                __TBB_ASSERT(load<relaxed>() != segment_allocated(),"transition from \"allocated\" to \"allocation failed\" state looks non-logical");
                array.store<M>(internal::vector_allocation_error_flag);
            }

            template<memory_semantics M>
            void store(void* allocated_segment_pointer) __TBB_NOEXCEPT(true) {
                __TBB_ASSERT(segment_value_t(allocated_segment_pointer) == segment_allocated(),
                     "other overloads of store should be used for marking segment as not_used or allocation_failed" );
                array.store<M>(allocated_segment_pointer);
            }

#if TBB_USE_ASSERT
            ~segment_t() {
                __TBB_ASSERT(load<relaxed>() != segment_allocated(), "should have been freed by clear" );
            }
#endif /* TBB_USE_ASSERT */
        };
        friend void swap(segment_t & , segment_t & ) __TBB_NOEXCEPT(true);

        // Data fields

        void* (*vector_allocator_ptr)(concurrent_vector_base_v3 &, size_t);

        atomic<size_type> my_first_block;

        atomic<size_type> my_early_size;

        atomic<segment_t*> my_segment;

        segment_t my_storage[pointers_per_short_table];

        // Methods

        concurrent_vector_base_v3() {
            //Here the semantic is intentionally relaxed.
            //The reason this is next:
            //Object that is in middle of construction (i.e. its constructor is not yet finished)
            //cannot be used concurrently until the construction is finished.
            //Thus to flag other threads that construction is finished, some synchronization with
            //acquire-release semantic should be done by the (external) code that uses the vector.
            //So, no need to do the synchronization inside the vector.

            my_early_size.store<relaxed>(0);
            my_first_block.store<relaxed>(0); // here is not default_initial_segments
            my_segment.store<relaxed>(my_storage);
        }

        __TBB_EXPORTED_METHOD ~concurrent_vector_base_v3();

        //these helpers methods use the fact that segments are allocated so
        //that every segment size is a (increasing) power of 2.
        //with one exception 0 segment has size of 2 as well segment 1;
        //e.g. size of segment with index of 3 is 2^3=8;
        static segment_index_t segment_index_of( size_type index ) {
            return segment_index_t( __TBB_Log2( index|1 ) );
        }

        static segment_index_t segment_base( segment_index_t k ) {
            return (segment_index_t(1)<<k & ~segment_index_t(1));
        }

        static inline segment_index_t segment_base_index_of( segment_index_t &index ) {
            segment_index_t k = segment_index_of( index );
            index -= segment_base(k);
            return k;
        }

        static size_type segment_size( segment_index_t k ) {
            return segment_index_t(1)<<k; // fake value for k==0
        }


        static bool is_first_element_in_segment(size_type element_index){
            //check if element_index is a power of 2 that is at least 2.
            //The idea is to detect if the iterator crosses a segment boundary,
            //and 2 is the minimal index for which it's true
            __TBB_ASSERT(element_index, "there should be no need to call "
                                        "is_first_element_in_segment for 0th element" );
            return is_power_of_two_at_least( element_index, 2 );
        }

        typedef void (__TBB_EXPORTED_FUNC *internal_array_op1)(void* begin, size_type n );

        typedef void (__TBB_EXPORTED_FUNC *internal_array_op2)(void* dst, const void* src, size_type n );

        struct internal_segments_table {
            segment_index_t first_block;
            segment_t table[pointers_per_long_table];
        };

        void __TBB_EXPORTED_METHOD internal_reserve( size_type n, size_type element_size, size_type max_size );
        size_type __TBB_EXPORTED_METHOD internal_capacity() const;
        void internal_grow( size_type start, size_type finish, size_type element_size, internal_array_op2 init, const void *src );
        size_type __TBB_EXPORTED_METHOD internal_grow_by( size_type delta, size_type element_size, internal_array_op2 init, const void *src );
        void* __TBB_EXPORTED_METHOD internal_push_back( size_type element_size, size_type& index );
        segment_index_t __TBB_EXPORTED_METHOD internal_clear( internal_array_op1 destroy );
        void* __TBB_EXPORTED_METHOD internal_compact( size_type element_size, void *table, internal_array_op1 destroy, internal_array_op2 copy );
        void __TBB_EXPORTED_METHOD internal_copy( const concurrent_vector_base_v3& src, size_type element_size, internal_array_op2 copy );
        void __TBB_EXPORTED_METHOD internal_assign( const concurrent_vector_base_v3& src, size_type element_size,
                              internal_array_op1 destroy, internal_array_op2 assign, internal_array_op2 copy );
        void __TBB_EXPORTED_METHOD internal_throw_exception(size_type) const;
        void __TBB_EXPORTED_METHOD internal_swap(concurrent_vector_base_v3& v);

        void __TBB_EXPORTED_METHOD internal_resize( size_type n, size_type element_size, size_type max_size, const void *src,
                                                    internal_array_op1 destroy, internal_array_op2 init );
        size_type __TBB_EXPORTED_METHOD internal_grow_to_at_least_with_result( size_type new_size, size_type element_size, internal_array_op2 init, const void *src );

        void __TBB_EXPORTED_METHOD internal_grow_to_at_least( size_type new_size, size_type element_size, internal_array_op2 init, const void *src );
private:
        class helper;
        friend class helper;

        template<typename Container, typename Value>
        friend class vector_iterator;

    };

    inline void swap(concurrent_vector_base_v3::segment_t & lhs, concurrent_vector_base_v3::segment_t & rhs) __TBB_NOEXCEPT(true) {
        lhs.swap(rhs);
    }

    typedef concurrent_vector_base_v3 concurrent_vector_base;


    template<typename Container, typename Value>
    class vector_iterator
    {
        Container* my_vector;

        size_t my_index;


        mutable Value* my_item;

        template<typename C, typename T>
        friend vector_iterator<C,T> operator+( ptrdiff_t offset, const vector_iterator<C,T>& v );

        template<typename C, typename T, typename U>
        friend bool operator==( const vector_iterator<C,T>& i, const vector_iterator<C,U>& j );

        template<typename C, typename T, typename U>
        friend bool operator<( const vector_iterator<C,T>& i, const vector_iterator<C,U>& j );

        template<typename C, typename T, typename U>
        friend ptrdiff_t operator-( const vector_iterator<C,T>& i, const vector_iterator<C,U>& j );

        template<typename C, typename U>
        friend class internal::vector_iterator;

#if !__TBB_TEMPLATE_FRIENDS_BROKEN
        template<typename T, class A>
        friend class tbb::concurrent_vector;
#else
public:
#endif

        vector_iterator( const Container& vector, size_t index, void *ptr = 0 ) :
            my_vector(const_cast<Container*>(&vector)),
            my_index(index),
            my_item(static_cast<Value*>(ptr))
        {}

    public:
        vector_iterator() : my_vector(NULL), my_index(~size_t(0)), my_item(NULL) {}

        vector_iterator( const vector_iterator<Container,typename Container::value_type>& other ) :
            my_vector(other.my_vector),
            my_index(other.my_index),
            my_item(other.my_item)
        {}

        vector_iterator operator+( ptrdiff_t offset ) const {
            return vector_iterator( *my_vector, my_index+offset );
        }
        vector_iterator &operator+=( ptrdiff_t offset ) {
            my_index+=offset;
            my_item = NULL;
            return *this;
        }
        vector_iterator operator-( ptrdiff_t offset ) const {
            return vector_iterator( *my_vector, my_index-offset );
        }
        vector_iterator &operator-=( ptrdiff_t offset ) {
            my_index-=offset;
            my_item = NULL;
            return *this;
        }
        Value& operator*() const {
            Value* item = my_item;
            if( !item ) {
                item = my_item = &my_vector->internal_subscript(my_index);
            }
            __TBB_ASSERT( item==&my_vector->internal_subscript(my_index), "corrupt cache" );
            return *item;
        }
        Value& operator[]( ptrdiff_t k ) const {
            return my_vector->internal_subscript(my_index+k);
        }
        Value* operator->() const {return &operator*();}

        vector_iterator& operator++() {
            size_t element_index = ++my_index;
            if( my_item ) {
                //TODO: consider using of knowledge about "first_block optimization" here as well?
                if( concurrent_vector_base::is_first_element_in_segment(element_index)) {
                    //if the iterator crosses a segment boundary, the pointer become invalid
                    //as possibly next segment is in another memory location
                    my_item= NULL;
                } else {
                    ++my_item;
                }
            }
            return *this;
        }

        vector_iterator& operator--() {
            __TBB_ASSERT( my_index>0, "operator--() applied to iterator already at beginning of concurrent_vector" );
            size_t element_index = my_index--;
            if( my_item ) {
                if(concurrent_vector_base::is_first_element_in_segment(element_index)) {
                    //if the iterator crosses a segment boundary, the pointer become invalid
                    //as possibly next segment is in another memory location
                    my_item= NULL;
                } else {
                    --my_item;
                }
            }
            return *this;
        }

        vector_iterator operator++(int) {
            vector_iterator result = *this;
            operator++();
            return result;
        }

        vector_iterator operator--(int) {
            vector_iterator result = *this;
            operator--();
            return result;
        }

        // STL support

        typedef ptrdiff_t difference_type;
        typedef Value value_type;
        typedef Value* pointer;
        typedef Value& reference;
        typedef std::random_access_iterator_tag iterator_category;
    };

    template<typename Container, typename T>
    vector_iterator<Container,T> operator+( ptrdiff_t offset, const vector_iterator<Container,T>& v ) {
        return vector_iterator<Container,T>( *v.my_vector, v.my_index+offset );
    }

    template<typename Container, typename T, typename U>
    bool operator==( const vector_iterator<Container,T>& i, const vector_iterator<Container,U>& j ) {
        return i.my_index==j.my_index && i.my_vector == j.my_vector;
    }

    template<typename Container, typename T, typename U>
    bool operator!=( const vector_iterator<Container,T>& i, const vector_iterator<Container,U>& j ) {
        return !(i==j);
    }

    template<typename Container, typename T, typename U>
    bool operator<( const vector_iterator<Container,T>& i, const vector_iterator<Container,U>& j ) {
        return i.my_index<j.my_index;
    }

    template<typename Container, typename T, typename U>
    bool operator>( const vector_iterator<Container,T>& i, const vector_iterator<Container,U>& j ) {
        return j<i;
    }

    template<typename Container, typename T, typename U>
    bool operator>=( const vector_iterator<Container,T>& i, const vector_iterator<Container,U>& j ) {
        return !(i<j);
    }

    template<typename Container, typename T, typename U>
    bool operator<=( const vector_iterator<Container,T>& i, const vector_iterator<Container,U>& j ) {
        return !(j<i);
    }

    template<typename Container, typename T, typename U>
    ptrdiff_t operator-( const vector_iterator<Container,T>& i, const vector_iterator<Container,U>& j ) {
        return ptrdiff_t(i.my_index)-ptrdiff_t(j.my_index);
    }

    template<typename T, class A>
    class allocator_base {
    public:
        typedef typename A::template
            rebind<T>::other allocator_type;
        allocator_type my_allocator;

        allocator_base(const allocator_type &a = allocator_type() ) : my_allocator(a) {}

    };

} // namespace internal


template<typename T, class A>
class concurrent_vector: protected internal::allocator_base<T, A>,
                         private internal::concurrent_vector_base {
private:
    template<typename I>
    class generic_range_type: public blocked_range<I> {
    public:
        typedef T value_type;
        typedef T& reference;
        typedef const T& const_reference;
        typedef I iterator;
        typedef ptrdiff_t difference_type;
        generic_range_type( I begin_, I end_, size_t grainsize_ = 1) : blocked_range<I>(begin_,end_,grainsize_) {}
        template<typename U>
        generic_range_type( const generic_range_type<U>& r) : blocked_range<I>(r.begin(),r.end(),r.grainsize()) {}
        generic_range_type( generic_range_type& r, split ) : blocked_range<I>(r,split()) {}
    };

    template<typename C, typename U>
    friend class internal::vector_iterator;

public:
    //------------------------------------------------------------------------
    // STL compatible types
    //------------------------------------------------------------------------
    typedef internal::concurrent_vector_base_v3::size_type size_type;
    typedef typename internal::allocator_base<T, A>::allocator_type allocator_type;

    typedef T value_type;
    typedef ptrdiff_t difference_type;
    typedef T& reference;
    typedef const T& const_reference;
    typedef T *pointer;
    typedef const T *const_pointer;

    typedef internal::vector_iterator<concurrent_vector,T> iterator;
    typedef internal::vector_iterator<concurrent_vector,const T> const_iterator;

#if !defined(_MSC_VER) || _CPPLIB_VER>=300
    // Assume ISO standard definition of std::reverse_iterator
    typedef std::reverse_iterator<iterator> reverse_iterator;
    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
#else
    // Use non-standard std::reverse_iterator
    typedef std::reverse_iterator<iterator,T,T&,T*> reverse_iterator;
    typedef std::reverse_iterator<const_iterator,T,const T&,const T*> const_reverse_iterator;
#endif /* defined(_MSC_VER) && (_MSC_VER<1300) */

    //------------------------------------------------------------------------
    // Parallel algorithm support
    //------------------------------------------------------------------------
    typedef generic_range_type<iterator> range_type;
    typedef generic_range_type<const_iterator> const_range_type;

    //------------------------------------------------------------------------
    // STL compatible constructors & destructors
    //------------------------------------------------------------------------

    explicit concurrent_vector(const allocator_type &a = allocator_type())
        : internal::allocator_base<T, A>(a), internal::concurrent_vector_base()
    {
        vector_allocator_ptr = &internal_allocator;
    }

    //Constructors are not required to have synchronization
    //(for more details see comment in the concurrent_vector_base constructor).
#if __TBB_INITIALIZER_LISTS_PRESENT
    concurrent_vector(std::initializer_list<T> init_list, const allocator_type &a = allocator_type())
        : internal::allocator_base<T, A>(a), internal::concurrent_vector_base()
    {
        vector_allocator_ptr = &internal_allocator;
        __TBB_TRY {
            internal_assign_iterators(init_list.begin(), init_list.end());
        } __TBB_CATCH(...) {
            segment_t *table = my_segment.load<relaxed>();;
            internal_free_segments( table, internal_clear(&destroy_array), my_first_block.load<relaxed>());
            __TBB_RETHROW();
        }

    }
#endif //# __TBB_INITIALIZER_LISTS_PRESENT

    concurrent_vector( const concurrent_vector& vector, const allocator_type& a = allocator_type() )
        : internal::allocator_base<T, A>(a), internal::concurrent_vector_base()
    {
        vector_allocator_ptr = &internal_allocator;
        __TBB_TRY {
            internal_copy(vector, sizeof(T), &copy_array);
        } __TBB_CATCH(...) {
            segment_t *table = my_segment.load<relaxed>();
            internal_free_segments( table, internal_clear(&destroy_array), my_first_block.load<relaxed>());
            __TBB_RETHROW();
        }
    }

#if __TBB_CPP11_RVALUE_REF_PRESENT
    //TODO add __TBB_NOEXCEPT(true) and static_assert(std::has_nothrow_move_constructor<A>::value)
    concurrent_vector( concurrent_vector&& source)
        : internal::allocator_base<T, A>(std::move(source)), internal::concurrent_vector_base()
    {
        vector_allocator_ptr = &internal_allocator;
        concurrent_vector_base_v3::internal_swap(source);
    }

    concurrent_vector( concurrent_vector&& source, const allocator_type& a)
        : internal::allocator_base<T, A>(a), internal::concurrent_vector_base()
    {
        vector_allocator_ptr = &internal_allocator;
        //C++ standard requires instances of an allocator being compared for equality,
        //which means that memory allocated by one instance is possible to deallocate with the other one.
        if (a == source.my_allocator) {
            concurrent_vector_base_v3::internal_swap(source);
        } else {
            __TBB_TRY {
                internal_copy(source, sizeof(T), &move_array);
            } __TBB_CATCH(...) {
                segment_t *table = my_segment.load<relaxed>();
                internal_free_segments( table, internal_clear(&destroy_array), my_first_block.load<relaxed>());
                __TBB_RETHROW();
            }
        }
    }

#endif

    template<class M>
    concurrent_vector( const concurrent_vector<T, M>& vector, const allocator_type& a = allocator_type() )
        : internal::allocator_base<T, A>(a), internal::concurrent_vector_base()
    {
        vector_allocator_ptr = &internal_allocator;
        __TBB_TRY {
            internal_copy(vector.internal_vector_base(), sizeof(T), &copy_array);
        } __TBB_CATCH(...) {
            segment_t *table = my_segment.load<relaxed>();
            internal_free_segments( table, internal_clear(&destroy_array), my_first_block.load<relaxed>() );
            __TBB_RETHROW();
        }
    }

    explicit concurrent_vector(size_type n)
    {
        vector_allocator_ptr = &internal_allocator;
        __TBB_TRY {
            internal_resize( n, sizeof(T), max_size(), NULL, &destroy_array, &initialize_array );
        } __TBB_CATCH(...) {
            segment_t *table = my_segment.load<relaxed>();
            internal_free_segments( table, internal_clear(&destroy_array), my_first_block.load<relaxed>() );
            __TBB_RETHROW();
        }
    }

    concurrent_vector(size_type n, const_reference t, const allocator_type& a = allocator_type())
        : internal::allocator_base<T, A>(a)
    {
        vector_allocator_ptr = &internal_allocator;
        __TBB_TRY {
            internal_resize( n, sizeof(T), max_size(), static_cast<const void*>(&t), &destroy_array, &initialize_array_by );
        } __TBB_CATCH(...) {
            segment_t *table = my_segment.load<relaxed>();
            internal_free_segments( table, internal_clear(&destroy_array), my_first_block.load<relaxed>() );
            __TBB_RETHROW();
        }
    }

    template<class I>
    concurrent_vector(I first, I last, const allocator_type &a = allocator_type())
        : internal::allocator_base<T, A>(a)
    {
        vector_allocator_ptr = &internal_allocator;
        __TBB_TRY {
            internal_assign_range(first, last, static_cast<is_integer_tag<std::numeric_limits<I>::is_integer> *>(0) );
        } __TBB_CATCH(...) {
            segment_t *table = my_segment.load<relaxed>();
            internal_free_segments( table, internal_clear(&destroy_array), my_first_block.load<relaxed>() );
            __TBB_RETHROW();
        }
    }

    concurrent_vector& operator=( const concurrent_vector& vector ) {
        if( this != &vector )
            internal_assign(vector, sizeof(T), &destroy_array, &assign_array, &copy_array);
        return *this;
    }

#if __TBB_CPP11_RVALUE_REF_PRESENT
    //TODO: add __TBB_NOEXCEPT()
    concurrent_vector& operator=( concurrent_vector&& other ) {
        __TBB_ASSERT(this != &other, "Move assignment to itself is prohibited ");
        typedef typename tbb::internal::allocator_traits<A>::propagate_on_container_move_assignment pocma_t;
        if(pocma_t::value || this->my_allocator == other.my_allocator) {
            concurrent_vector trash (std::move(*this));
            internal_swap(other);
            if (pocma_t::value) {
                this->my_allocator = std::move(other.my_allocator);
            }
        } else {
            internal_assign(other, sizeof(T), &destroy_array, &move_assign_array, &move_array);
        }
        return *this;
    }
#endif
    //TODO: add an template assignment operator? (i.e. with different element type)

    template<class M>
    concurrent_vector& operator=( const concurrent_vector<T, M>& vector ) {
        if( static_cast<void*>( this ) != static_cast<const void*>( &vector ) )
            internal_assign(vector.internal_vector_base(),
                sizeof(T), &destroy_array, &assign_array, &copy_array);
        return *this;
    }

#if __TBB_INITIALIZER_LISTS_PRESENT
    concurrent_vector& operator=( std::initializer_list<T> init_list ) {
        internal_clear(&destroy_array);
        internal_assign_iterators(init_list.begin(), init_list.end());
        return *this;
    }
#endif //#if __TBB_INITIALIZER_LISTS_PRESENT

    //------------------------------------------------------------------------
    // Concurrent operations
    //------------------------------------------------------------------------

    iterator grow_by( size_type delta ) {
        return iterator(*this, delta ? internal_grow_by( delta, sizeof(T), &initialize_array, NULL ) : my_early_size.load());
    }


    iterator grow_by( size_type delta, const_reference t ) {
        return iterator(*this, delta ? internal_grow_by( delta, sizeof(T), &initialize_array_by, static_cast<const void*>(&t) ) : my_early_size.load());
    }

    template<typename I>
    iterator grow_by( I first, I last ) {
        typename std::iterator_traits<I>::difference_type delta = std::distance(first, last);
        __TBB_ASSERT( delta >= 0, NULL);

        return iterator(*this, delta ? internal_grow_by(delta, sizeof(T), &copy_range<I>, static_cast<const void*>(&first)) : my_early_size.load());
    }

#if __TBB_INITIALIZER_LISTS_PRESENT

    iterator grow_by( std::initializer_list<T> init_list ) {
        return grow_by( init_list.begin(), init_list.end() );
    }
#endif //#if __TBB_INITIALIZER_LISTS_PRESENT


    iterator grow_to_at_least( size_type n ) {
        size_type m=0;
        if( n ) {
            m = internal_grow_to_at_least_with_result( n, sizeof(T), &initialize_array, NULL );
            if( m>n ) m=n;
        }
        return iterator(*this, m);
    };

    iterator grow_to_at_least( size_type n, const_reference t ) {
        size_type m=0;
        if( n ) {
            m = internal_grow_to_at_least_with_result( n, sizeof(T), &initialize_array_by, &t);
            if( m>n ) m=n;
        }
        return iterator(*this, m);
    };


    iterator push_back( const_reference item )
    {
        push_back_helper prolog(*this);
        new(prolog.internal_push_back_result()) T(item);
        return prolog.return_iterator_and_dismiss();
    }

#if    __TBB_CPP11_RVALUE_REF_PRESENT

    iterator push_back(  T&& item )
    {
        push_back_helper prolog(*this);
        new(prolog.internal_push_back_result()) T(std::move(item));
        return prolog.return_iterator_and_dismiss();
    }
#if __TBB_CPP11_VARIADIC_TEMPLATES_PRESENT

    template<typename... Args>
    iterator emplace_back(  Args&&... args )
    {
        push_back_helper prolog(*this);
        new(prolog.internal_push_back_result()) T(std::forward<Args>(args)...);
        return prolog.return_iterator_and_dismiss();
    }
#endif //__TBB_CPP11_VARIADIC_TEMPLATES_PRESENT
#endif //__TBB_CPP11_RVALUE_REF_PRESENT

    reference operator[]( size_type index ) {
        return internal_subscript(index);
    }

    const_reference operator[]( size_type index ) const {
        return internal_subscript(index);
    }

    reference at( size_type index ) {
        return internal_subscript_with_exceptions(index);
    }

    const_reference at( size_type index ) const {
        return internal_subscript_with_exceptions(index);
    }

    range_type range( size_t grainsize = 1 ) {
        return range_type( begin(), end(), grainsize );
    }

    const_range_type range( size_t grainsize = 1 ) const {
        return const_range_type( begin(), end(), grainsize );
    }

    //------------------------------------------------------------------------
    // Capacity
    //------------------------------------------------------------------------
    size_type size() const {
        size_type sz = my_early_size, cp = internal_capacity();
        return cp < sz ? cp : sz;
    }

    bool empty() const {return !my_early_size;}

    size_type capacity() const {return internal_capacity();}


    void reserve( size_type n ) {
        if( n )
            internal_reserve(n, sizeof(T), max_size());
    }

    void resize( size_type n ) {
        internal_resize( n, sizeof(T), max_size(), NULL, &destroy_array, &initialize_array );
    }

    void resize( size_type n, const_reference t ) {
        internal_resize( n, sizeof(T), max_size(), static_cast<const void*>(&t), &destroy_array, &initialize_array_by );
    }

    void shrink_to_fit();

    size_type max_size() const {return (~size_type(0))/sizeof(T);}

    //------------------------------------------------------------------------
    // STL support
    //------------------------------------------------------------------------

    iterator begin() {return iterator(*this,0);}
    iterator end() {return iterator(*this,size());}
    const_iterator begin() const {return const_iterator(*this,0);}
    const_iterator end() const {return const_iterator(*this,size());}
    const_iterator cbegin() const {return const_iterator(*this,0);}
    const_iterator cend() const {return const_iterator(*this,size());}
    reverse_iterator rbegin() {return reverse_iterator(end());}
    reverse_iterator rend() {return reverse_iterator(begin());}
    const_reverse_iterator rbegin() const {return const_reverse_iterator(end());}
    const_reverse_iterator rend() const {return const_reverse_iterator(begin());}
    const_reverse_iterator crbegin() const {return const_reverse_iterator(end());}
    const_reverse_iterator crend() const {return const_reverse_iterator(begin());}
    reference front() {
        __TBB_ASSERT( size()>0, NULL);
        const segment_value_t& segment_value = my_segment[0].template load<relaxed>();
        return (segment_value.template pointer<T>())[0];
    }
    const_reference front() const {
        __TBB_ASSERT( size()>0, NULL);
        const segment_value_t& segment_value = my_segment[0].template load<relaxed>();
        return (segment_value.template pointer<const T>())[0];
    }
    reference back() {
        __TBB_ASSERT( size()>0, NULL);
        return internal_subscript( size()-1 );
    }
    const_reference back() const {
        __TBB_ASSERT( size()>0, NULL);
        return internal_subscript( size()-1 );
    }
    allocator_type get_allocator() const { return this->my_allocator; }

    void assign(size_type n, const_reference t) {
        clear();
        internal_resize( n, sizeof(T), max_size(), static_cast<const void*>(&t), &destroy_array, &initialize_array_by );
    }

    template<class I>
    void assign(I first, I last) {
        clear(); internal_assign_range( first, last, static_cast<is_integer_tag<std::numeric_limits<I>::is_integer> *>(0) );
    }

#if __TBB_INITIALIZER_LISTS_PRESENT
    void assign(std::initializer_list<T> init_list) {
        clear(); internal_assign_iterators( init_list.begin(), init_list.end());
    }
#endif //# __TBB_INITIALIZER_LISTS_PRESENT

    void swap(concurrent_vector &vector) {
        using std::swap;
        if( this != &vector ) {
            concurrent_vector_base_v3::internal_swap(static_cast<concurrent_vector_base_v3&>(vector));
            swap(this->my_allocator, vector.my_allocator);
        }
    }


    void clear() {
        internal_clear(&destroy_array);
    }

    ~concurrent_vector() {
        segment_t *table = my_segment.load<relaxed>();
        internal_free_segments( table, internal_clear(&destroy_array), my_first_block.load<relaxed>() );
        // base class destructor call should be then
    }

    const internal::concurrent_vector_base_v3 &internal_vector_base() const { return *this; }
private:
    static void *internal_allocator(internal::concurrent_vector_base_v3 &vb, size_t k) {
        return static_cast<concurrent_vector<T, A>&>(vb).my_allocator.allocate(k);
    }
    void internal_free_segments(segment_t table[], segment_index_t k, segment_index_t first_block);

    T& internal_subscript( size_type index ) const;

    T& internal_subscript_with_exceptions( size_type index ) const;

    void internal_assign_n(size_type n, const_pointer p) {
        internal_resize( n, sizeof(T), max_size(), static_cast<const void*>(p), &destroy_array, p? &initialize_array_by : &initialize_array );
    }

    template<bool B> class is_integer_tag;

    template<class I>
    void internal_assign_range(I first, I last, is_integer_tag<true> *) {
        internal_assign_n(static_cast<size_type>(first), &static_cast<T&>(last));
    }
    template<class I>
    void internal_assign_range(I first, I last, is_integer_tag<false> *) {
        internal_assign_iterators(first, last);
    }
    template<class I>
    void internal_assign_iterators(I first, I last);

    //these functions are marked __TBB_EXPORTED_FUNC as they are called from within the library

    static void __TBB_EXPORTED_FUNC initialize_array( void* begin, const void*, size_type n );

    static void __TBB_EXPORTED_FUNC initialize_array_by( void* begin, const void* src, size_type n );

    static void __TBB_EXPORTED_FUNC copy_array( void* dst, const void* src, size_type n );

#if __TBB_MOVE_IF_NOEXCEPT_PRESENT
    static void __TBB_EXPORTED_FUNC move_array_if_noexcept( void* dst, const void* src, size_type n );
#endif //__TBB_MOVE_IF_NO_EXCEPT_PRESENT

#if __TBB_CPP11_RVALUE_REF_PRESENT
    static void __TBB_EXPORTED_FUNC move_array( void* dst, const void* src, size_type n );

    static void __TBB_EXPORTED_FUNC move_assign_array( void* dst, const void* src, size_type n );
#endif
    template<typename Iterator>
    static void __TBB_EXPORTED_FUNC copy_range( void* dst, const void* p_type_erased_iterator, size_type n );

    static void __TBB_EXPORTED_FUNC assign_array( void* dst, const void* src, size_type n );

    static void __TBB_EXPORTED_FUNC destroy_array( void* begin, size_type n );

    class internal_loop_guide : internal::no_copy {
    public:
        const pointer array;
        const size_type n;
        size_type i;

        static const T* as_const_pointer(const void *ptr) { return static_cast<const T *>(ptr); }
        static T* as_pointer(const void *src) { return static_cast<T*>(const_cast<void *>(src)); }

        internal_loop_guide(size_type ntrials, void *ptr)
            : array(as_pointer(ptr)), n(ntrials), i(0) {}
        void init() {   for(; i < n; ++i) new( &array[i] ) T(); }
        void init(const void *src) { for(; i < n; ++i) new( &array[i] ) T(*as_const_pointer(src)); }
        void copy(const void *src) { for(; i < n; ++i) new( &array[i] ) T(as_const_pointer(src)[i]); }
        void assign(const void *src) { for(; i < n; ++i) array[i] = as_const_pointer(src)[i]; }
#if __TBB_CPP11_RVALUE_REF_PRESENT
        void move_assign(const void *src)       { for(; i < n; ++i) array[i]         =  std::move(as_pointer(src)[i]);   }
        void move_construct(const void *src)    { for(; i < n; ++i) new( &array[i] ) T( std::move(as_pointer(src)[i]) ); }
#endif
#if __TBB_MOVE_IF_NOEXCEPT_PRESENT
        void move_construct_if_noexcept(const void *src)    { for(; i < n; ++i) new( &array[i] ) T( std::move_if_noexcept(as_pointer(src)[i]) ); }
#endif //__TBB_MOVE_IF_NOEXCEPT_PRESENT

        //TODO: rename to construct_range
        template<class I> void iterate(I &src) { for(; i < n; ++i, ++src) new( &array[i] ) T( *src ); }
        ~internal_loop_guide() {
            if(i < n) {// if an exception was raised, fill the rest of items with zeros
                internal::handle_unconstructed_elements(array+i, n-i);
            }
        }
    };

    struct push_back_helper : internal::no_copy{
        struct element_construction_guard : internal::no_copy{
            pointer element;

            element_construction_guard(pointer an_element) : element (an_element){}
            void dismiss(){ element = NULL; }
            ~element_construction_guard(){
                if (element){
                    internal::handle_unconstructed_elements(element, 1);
                }
            }
        };

        concurrent_vector & v;
        size_type k;
        element_construction_guard g;

        push_back_helper(concurrent_vector & vector) :
            v(vector),
            g (static_cast<T*>(v.internal_push_back(sizeof(T),k)))
        {}

        pointer internal_push_back_result(){ return g.element;}
        iterator return_iterator_and_dismiss(){
            pointer ptr = g.element;
            g.dismiss();
            return iterator(v, k, ptr);
        }
    };
};

#if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
#pragma warning (push)
#pragma warning (disable: 4701) // potentially uninitialized local variable "old"
#endif
template<typename T, class A>
void concurrent_vector<T, A>::shrink_to_fit() {
    internal_segments_table old;
    __TBB_TRY {
        internal_array_op2 copy_or_move_array =
#if __TBB_MOVE_IF_NOEXCEPT_PRESENT
                &move_array_if_noexcept
#else
                &copy_array
#endif
        ;
        if( internal_compact( sizeof(T), &old, &destroy_array, copy_or_move_array ) )
            internal_free_segments( old.table, pointers_per_long_table, old.first_block ); // free joined and unnecessary segments
    } __TBB_CATCH(...) {
        if( old.first_block ) // free segment allocated for compacting. Only for support of exceptions in ctor of user T[ype]
            internal_free_segments( old.table, 1, old.first_block );
        __TBB_RETHROW();
    }
}
#if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
#pragma warning (pop)
#endif // warning 4701 is back

template<typename T, class A>
void concurrent_vector<T, A>::internal_free_segments(segment_t table[], segment_index_t k, segment_index_t first_block) {
    // Free the arrays
    while( k > first_block ) {
        --k;
        segment_value_t segment_value = table[k].load<relaxed>();
        table[k].store<relaxed>(segment_not_used());
        if( segment_value == segment_allocated() ) // check for correct segment pointer
            this->my_allocator.deallocate( (segment_value.pointer<T>()), segment_size(k) );
    }
    segment_value_t segment_value = table[0].load<relaxed>();
    if( segment_value == segment_allocated() ) {
        __TBB_ASSERT( first_block > 0, NULL );
        while(k > 0) table[--k].store<relaxed>(segment_not_used());
        this->my_allocator.deallocate( (segment_value.pointer<T>()), segment_size(first_block) );
    }
}

template<typename T, class A>
T& concurrent_vector<T, A>::internal_subscript( size_type index ) const {
    //TODO: unify both versions of internal_subscript
    __TBB_ASSERT( index < my_early_size, "index out of bounds" );
    size_type j = index;
    segment_index_t k = segment_base_index_of( j );
    __TBB_ASSERT( my_segment.load<acquire>() != my_storage || k < pointers_per_short_table, "index is being allocated" );
    //no need in load with acquire (load<acquire>) since thread works in own space or gets
    //the information about added elements via some form of external synchronization
    //TODO: why not make a load of my_segment relaxed as well ?
    //TODO: add an assertion that my_segment[k] is properly aligned to please ITT
    segment_value_t segment_value =  my_segment[k].template load<relaxed>();
    __TBB_ASSERT( segment_value != segment_allocation_failed(), "the instance is broken by bad allocation. Use at() instead" );
    __TBB_ASSERT( segment_value != segment_not_used(), "index is being allocated" );
    return (( segment_value.pointer<T>()))[j];
}

template<typename T, class A>
T& concurrent_vector<T, A>::internal_subscript_with_exceptions( size_type index ) const {
    if( index >= my_early_size )
        internal::throw_exception(internal::eid_out_of_range); // throw std::out_of_range
    size_type j = index;
    segment_index_t k = segment_base_index_of( j );
    //TODO: refactor this condition into separate helper function, e.g. fits_into_small_table
    if( my_segment.load<acquire>() == my_storage && k >= pointers_per_short_table )
        internal::throw_exception(internal::eid_segment_range_error); // throw std::range_error
    // no need in load with acquire (load<acquire>) since thread works in own space or gets
    //the information about added elements via some form of external synchronization
    //TODO: why not make a load of my_segment relaxed as well ?
    //TODO: add an assertion that my_segment[k] is properly aligned to please ITT
    segment_value_t segment_value =  my_segment[k].template load<relaxed>();
    enforce_segment_allocated(segment_value, internal::eid_index_range_error);
    return (segment_value.pointer<T>())[j];
}

template<typename T, class A> template<class I>
void concurrent_vector<T, A>::internal_assign_iterators(I first, I last) {
    __TBB_ASSERT(my_early_size == 0, NULL);
    size_type n = std::distance(first, last);
    if( !n ) return;
    internal_reserve(n, sizeof(T), max_size());
    my_early_size = n;
    segment_index_t k = 0;
    //TODO: unify segment iteration code with concurrent_base_v3::helper
    size_type sz = segment_size( my_first_block );
    while( sz < n ) {
        internal_loop_guide loop(sz, my_segment[k].template load<relaxed>().template pointer<void>());
        loop.iterate(first);
        n -= sz;
        if( !k ) k = my_first_block;
        else { ++k; sz <<= 1; }
    }
    internal_loop_guide loop(n, my_segment[k].template load<relaxed>().template pointer<void>());
    loop.iterate(first);
}

template<typename T, class A>
void concurrent_vector<T, A>::initialize_array( void* begin, const void *, size_type n ) {
    internal_loop_guide loop(n, begin); loop.init();
}

template<typename T, class A>
void concurrent_vector<T, A>::initialize_array_by( void* begin, const void *src, size_type n ) {
    internal_loop_guide loop(n, begin); loop.init(src);
}

template<typename T, class A>
void concurrent_vector<T, A>::copy_array( void* dst, const void* src, size_type n ) {
    internal_loop_guide loop(n, dst); loop.copy(src);
}

#if __TBB_CPP11_RVALUE_REF_PRESENT
template<typename T, class A>
void concurrent_vector<T, A>::move_array( void* dst, const void* src, size_type n ) {
    internal_loop_guide loop(n, dst); loop.move_construct(src);
}
template<typename T, class A>
void concurrent_vector<T, A>::move_assign_array( void* dst, const void* src, size_type n ) {
    internal_loop_guide loop(n, dst); loop.move_assign(src);
}
#endif

#if __TBB_MOVE_IF_NOEXCEPT_PRESENT
template<typename T, class A>
void concurrent_vector<T, A>::move_array_if_noexcept( void* dst, const void* src, size_type n ) {
    internal_loop_guide loop(n, dst); loop.move_construct_if_noexcept(src);
}
#endif //__TBB_MOVE_IF_NOEXCEPT_PRESENT

template<typename T, class A>
template<typename I>
void concurrent_vector<T, A>::copy_range( void* dst, const void* p_type_erased_iterator, size_type n ){
    I & iterator ((*const_cast<I*>(static_cast<const I*>(p_type_erased_iterator))));
    internal_loop_guide loop(n, dst); loop.iterate(iterator);
}

template<typename T, class A>
void concurrent_vector<T, A>::assign_array( void* dst, const void* src, size_type n ) {
    internal_loop_guide loop(n, dst); loop.assign(src);
}

#if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
    // Workaround for overzealous compiler warning
    #pragma warning (push)
    #pragma warning (disable: 4189)
#endif
template<typename T, class A>
void concurrent_vector<T, A>::destroy_array( void* begin, size_type n ) {
    T* array = static_cast<T*>(begin);
    for( size_type j=n; j>0; --j )
        array[j-1].~T(); // destructors are supposed to not throw any exceptions
}
#if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
    #pragma warning (pop)
#endif // warning 4189 is back

// concurrent_vector's template functions
template<typename T, class A1, class A2>
inline bool operator==(const concurrent_vector<T, A1> &a, const concurrent_vector<T, A2> &b) {
    //TODO: call size() only once per vector (in operator==)
    // Simply:    return a.size() == b.size() && std::equal(a.begin(), a.end(), b.begin());
    if(a.size() != b.size()) return false;
    typename concurrent_vector<T, A1>::const_iterator i(a.begin());
    typename concurrent_vector<T, A2>::const_iterator j(b.begin());
    for(; i != a.end(); ++i, ++j)
        if( !(*i == *j) ) return false;
    return true;
}

template<typename T, class A1, class A2>
inline bool operator!=(const concurrent_vector<T, A1> &a, const concurrent_vector<T, A2> &b)
{    return !(a == b); }

template<typename T, class A1, class A2>
inline bool operator<(const concurrent_vector<T, A1> &a, const concurrent_vector<T, A2> &b)
{    return (std::lexicographical_compare(a.begin(), a.end(), b.begin(), b.end())); }

template<typename T, class A1, class A2>
inline bool operator>(const concurrent_vector<T, A1> &a, const concurrent_vector<T, A2> &b)
{    return b < a; }

template<typename T, class A1, class A2>
inline bool operator<=(const concurrent_vector<T, A1> &a, const concurrent_vector<T, A2> &b)
{    return !(b < a); }

template<typename T, class A1, class A2>
inline bool operator>=(const concurrent_vector<T, A1> &a, const concurrent_vector<T, A2> &b)
{    return !(a < b); }

template<typename T, class A>
inline void swap(concurrent_vector<T, A> &a, concurrent_vector<T, A> &b)
{    a.swap( b ); }

} // namespace tbb

#if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
    #pragma warning (pop)
#endif // warning 4267,4127 are back

#endif /* __TBB_concurrent_vector_H */