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JohanMabilleJohanMabille
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Merge pull request #2768 from BioDataAnalysis/option_to_disable_temporary_object_in_assignment
Adding the ability to enable memory overlap check in assignment to avoid unneeded temporary memory allocation
2 parents a17f3de + 4507f14 commit d9c3782

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6 files changed

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‎CMakeLists.txt‎

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@@ -199,6 +199,7 @@ target_link_libraries(xtensor INTERFACE xtl)
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OPTION(XTENSOR_ENABLE_ASSERT "xtensor bound check" OFF)
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OPTION(XTENSOR_CHECK_DIMENSION "xtensor dimension check" OFF)
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OPTION(XTENSOR_FORCE_TEMPORARY_MEMORY_IN_ASSIGNMENTS "xtensor force the use of temporary memory when assigning instead of an automatic overlap check" ON)
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OPTION(BUILD_TESTS "xtensor test suite" OFF)
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OPTION(BUILD_BENCHMARK "xtensor benchmark" OFF)
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OPTION(DOWNLOAD_GTEST "build gtest from downloaded sources" OFF)
@@ -219,6 +220,10 @@ if(XTENSOR_CHECK_DIMENSION)
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add_definitions(-DXTENSOR_ENABLE_CHECK_DIMENSION)
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endif()
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if(XTENSOR_FORCE_TEMPORARY_MEMORY_IN_ASSIGNMENTS)
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add_definitions(-DXTENSOR_FORCE_TEMPORARY_MEMORY_IN_ASSIGNMENTS)
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endif()
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if(DEFAULT_COLUMN_MAJOR)
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add_definitions(-DXTENSOR_DEFAULT_LAYOUT=layout_type::column_major)
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endif()

‎include/xtensor/xbroadcast.hpp‎

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@@ -118,6 +118,29 @@ namespace xt
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return linear_end(c.expression());
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}
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/*************************************
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* overlapping_memory_checker_traits *
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*************************************/
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template <class E>
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struct overlapping_memory_checker_traits<
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E,
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std::enable_if_t<!has_memory_address<E>::value && is_specialization_of<xbroadcast, E>::value>>
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{
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static bool check_overlap(const E& expr, const memory_range& dst_range)
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{
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if (expr.size() == 0)
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{
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return false;
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}
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else
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{
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using ChildE = std::decay_t<decltype(expr.expression())>;
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return overlapping_memory_checker_traits<ChildE>::check_overlap(expr.expression(), dst_range);
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}
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}
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};
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/**
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* @class xbroadcast
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* @brief Broadcasted xexpression to a specified shape.

‎include/xtensor/xfunction.hpp‎

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@@ -162,6 +162,42 @@ namespace xt
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{
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};
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/*************************************
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* overlapping_memory_checker_traits *
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*************************************/
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template <class E>
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struct overlapping_memory_checker_traits<
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E,
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std::enable_if_t<!has_memory_address<E>::value && is_specialization_of<xfunction, E>::value>>
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{
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template <std::size_t I = 0, class... T, std::enable_if_t<(I == sizeof...(T)), int> = 0>
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static bool check_tuple(const std::tuple<T...>&, const memory_range&)
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{
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return false;
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}
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template <std::size_t I = 0, class... T, std::enable_if_t<(I < sizeof...(T)), int> = 0>
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static bool check_tuple(const std::tuple<T...>& t, const memory_range& dst_range)
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{
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using ChildE = std::decay_t<decltype(std::get<I>(t))>;
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return overlapping_memory_checker_traits<ChildE>::check_overlap(std::get<I>(t), dst_range)
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|| check_tuple<I + 1>(t, dst_range);
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}
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static bool check_overlap(const E& expr, const memory_range& dst_range)
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{
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if (expr.size() == 0)
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{
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return false;
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}
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else
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{
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return check_tuple(expr.arguments(), dst_range);
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}
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}
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};
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/*************
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* xfunction *
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*************/

‎include/xtensor/xgenerator.hpp‎

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@@ -76,6 +76,21 @@ namespace xt
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using size_type = std::size_t;
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};
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/*************************************
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* overlapping_memory_checker_traits *
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*************************************/
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template <class E>
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struct overlapping_memory_checker_traits<
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E,
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std::enable_if_t<!has_memory_address<E>::value && is_specialization_of<xgenerator, E>::value>>
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{
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static bool check_overlap(const E&, const memory_range&)
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{
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return false;
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}
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};
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/**
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* @class xgenerator
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* @brief Multidimensional function operating on indices.

‎include/xtensor/xsemantic.hpp‎

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@@ -217,6 +217,29 @@ namespace xt
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template <class E, class R = void>
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using disable_xcontainer_semantics = typename std::enable_if<!has_container_semantics<E>::value, R>::type;
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template <class D>
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class xview_semantic;
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template <class E>
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struct overlapping_memory_checker_traits<
226+
E,
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std::enable_if_t<!has_memory_address<E>::value && is_crtp_base_of<xview_semantic, E>::value>>
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{
229+
static bool check_overlap(const E& expr, const memory_range& dst_range)
230+
{
231+
if (expr.size() == 0)
232+
{
233+
return false;
234+
}
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else
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{
237+
using ChildE = std::decay_t<decltype(expr.expression())>;
238+
return overlapping_memory_checker_traits<ChildE>::check_overlap(expr.expression(), dst_range);
239+
}
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}
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};
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/**
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* @class xview_semantic
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* @brief Implementation of the xsemantic_base interface for
@@ -598,8 +621,22 @@ namespace xt
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template <class E>
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inline auto xsemantic_base<D>::operator=(const xexpression<E>& e) -> derived_type&
600623
{
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#ifdef XTENSOR_FORCE_TEMPORARY_MEMORY_IN_ASSIGNMENTS
601625
temporary_type tmp(e);
602626
return this->derived_cast().assign_temporary(std::move(tmp));
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#else
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auto&& this_derived = this->derived_cast();
629+
auto memory_checker = make_overlapping_memory_checker(this_derived);
630+
if (memory_checker.check_overlap(e.derived_cast()))
631+
{
632+
temporary_type tmp(e);
633+
return this_derived.assign_temporary(std::move(tmp));
634+
}
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else
636+
{
637+
return this->assign(e);
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}
639+
#endif
603640
}
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/**************************************

‎include/xtensor/xutils.hpp‎

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@@ -119,6 +119,20 @@ namespace xt
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using type = T;
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};
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/***************************************
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* is_specialization_of implementation *
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***************************************/
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126+
template <template <class...> class TT, class T>
127+
struct is_specialization_of : std::false_type
128+
{
129+
};
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131+
template <template <class...> class TT, class... Ts>
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struct is_specialization_of<TT, TT<Ts...>> : std::true_type
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{
134+
};
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/*******************************
123137
* remove_class implementation *
124138
*******************************/
@@ -860,6 +874,139 @@ namespace xt
860874
{
861875
};
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/*************************************
878+
* overlapping_memory_checker_traits *
879+
*************************************/
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881+
template <class T, class Enable = void>
882+
struct has_memory_address : std::false_type
883+
{
884+
};
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template <class T>
887+
struct has_memory_address<T, void_t<decltype(std::addressof(*std::declval<T>().begin()))>> : std::true_type
888+
{
889+
};
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891+
struct memory_range
892+
{
893+
// Checking pointer overlap is more correct in integer values,
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// for more explanation check https://devblogs.microsoft.com/oldnewthing/20170927-00/?p=97095
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const uintptr_t m_first = 0;
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const uintptr_t m_last = 0;
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explicit memory_range() = default;
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template <class T>
901+
explicit memory_range(T* first, T* last)
902+
: m_first(reinterpret_cast<uintptr_t>(last < first ? last : first))
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, m_last(reinterpret_cast<uintptr_t>(last < first ? first : last))
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{
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}
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template <class T>
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bool overlaps(T* first, T* last) const
909+
{
910+
if (first <= last)
911+
{
912+
return reinterpret_cast<uintptr_t>(first) <= m_last
913+
&& reinterpret_cast<uintptr_t>(last) >= m_first;
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}
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else
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{
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return reinterpret_cast<uintptr_t>(last) <= m_last
918+
&& reinterpret_cast<uintptr_t>(first) >= m_first;
919+
}
920+
}
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};
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923+
template <class E, class Enable = void>
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struct overlapping_memory_checker_traits
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{
926+
static bool check_overlap(const E&, const memory_range&)
927+
{
928+
return true;
929+
}
930+
};
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932+
template <class E>
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struct overlapping_memory_checker_traits<E, std::enable_if_t<has_memory_address<E>::value>>
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{
935+
static bool check_overlap(const E& expr, const memory_range& dst_range)
936+
{
937+
if (expr.size() == 0)
938+
{
939+
return false;
940+
}
941+
else
942+
{
943+
return dst_range.overlaps(std::addressof(*expr.begin()), std::addressof(*expr.rbegin()));
944+
}
945+
}
946+
};
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948+
struct overlapping_memory_checker_base
949+
{
950+
memory_range m_dst_range;
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952+
explicit overlapping_memory_checker_base() = default;
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explicit overlapping_memory_checker_base(memory_range dst_memory_range)
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: m_dst_range(std::move(dst_memory_range))
956+
{
957+
}
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959+
template <class E>
960+
bool check_overlap(const E& expr) const
961+
{
962+
if (!m_dst_range.m_first || !m_dst_range.m_last)
963+
{
964+
return false;
965+
}
966+
else
967+
{
968+
return overlapping_memory_checker_traits<E>::check_overlap(expr, m_dst_range);
969+
}
970+
}
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};
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973+
template <class Dst, class Enable = void>
974+
struct overlapping_memory_checker : overlapping_memory_checker_base
975+
{
976+
explicit overlapping_memory_checker(const Dst&)
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: overlapping_memory_checker_base()
978+
{
979+
}
980+
};
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982+
template <class Dst>
983+
struct overlapping_memory_checker<Dst, std::enable_if_t<has_memory_address<Dst>::value>>
984+
: overlapping_memory_checker_base
985+
{
986+
explicit overlapping_memory_checker(const Dst& aDst)
987+
: overlapping_memory_checker_base(
988+
[&]()
989+
{
990+
if (aDst.size() == 0)
991+
{
992+
return memory_range();
993+
}
994+
else
995+
{
996+
return memory_range(std::addressof(*aDst.begin()), std::addressof(*aDst.rbegin()));
997+
}
998+
}()
999+
)
1000+
{
1001+
}
1002+
};
1003+
1004+
template <class Dst>
1005+
auto make_overlapping_memory_checker(const Dst& a_dst)
1006+
{
1007+
return overlapping_memory_checker<Dst>(a_dst);
1008+
}
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8631010
/********************
8641011
* rebind_container *
8651012
********************/

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