Skip to content

Commit

Permalink
[SYCL] Add reduction overloads accepting span (#6019)
Browse files Browse the repository at this point in the history 
A new static member function "num_elements" is added to all reduction
specializations to distinguish between scalar reductions and array reductions.
A scalar reduction (all existing implementations of reduction) always
has (num_elements == 1); an array reduction (this new specialization) has
(num_elements == Extent), where Extent is the extent of the span.

If (num_elements > 1), the implementation currently reduces each element
separately. This allows array reductions to use the same amount of work-group
local memory as a scalar reduction using the same T, but at the expense of
additional synchronization calls.

The notion of a reducer's "dimensionality" is now tied to the dimensionality of
the reduction being performed (i.e. 0 for scalars, 1 for spans) and not to the
dimensionality of the input accessor/buffer. This will simplify extending
reductions to true multi-dimensional array reductions (i.e. with md_span).

In future, the code handling the reduction packs could be generalized to
handle more reduction/reducer types while making fewer assumptions about
the reduction algorithm.

Signed-off-by: John Pennycook john.pennycook@intel.com
  • Loading branch information
@Pennycook
Pennycook authored May 2, 2022
1 parent da017f8 commit 863383b
Show file tree
Hide file tree
Showing 4 changed files with 1,283 additions and 631 deletions.
16 changes: 8 additions & 8 deletions sycl/include/CL/sycl/handler.hpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -240,9 +240,9 @@ class RoundedRangeKernelWithKH {
namespace ext {
namespace oneapi {
namespace detail {
template <typename T, class BinaryOperation, int Dims, bool IsUSM,
access::placeholder IsPlaceholder>
class reduction_impl;
template <typename T, class BinaryOperation, int Dims, size_t Extent,
class Algorithm>
class reduction_impl_algo;

using cl::sycl::detail::enable_if_t;
using cl::sycl::detail::queue_impl;
Expand Down Expand Up @@ -2682,11 +2682,11 @@ class __SYCL_EXPORT handler {
// Make stream class friend to be able to keep the list of associated streams
friend class stream;
friend class detail::stream_impl;
// Make reduction_impl friend to store buffers and arrays created for it
// in handler from reduction_impl methods.
template <typename T, class BinaryOperation, int Dims, bool IsUSM,
access::placeholder IsPlaceholder>
friend class ext::oneapi::detail::reduction_impl;
// Make reduction friends to store buffers and arrays created for it
// in handler from reduction methods.
template <typename T, class BinaryOperation, int Dims, size_t Extent,
class Algorithm>
friend class ext::oneapi::detail::reduction_impl_algo;

// This method needs to call the method finalize().
template <typename Reduction, typename... RestT>
Expand Down
91 changes: 80 additions & 11 deletions sycl/include/CL/sycl/reduction.hpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,9 @@ namespace sycl {
template <typename T, typename AllocatorT, typename BinaryOperation>
std::enable_if_t<has_known_identity<BinaryOperation, T>::value,
ext::oneapi::detail::reduction_impl<
T, BinaryOperation, 1, false, access::placeholder::true_t>>
T, BinaryOperation, 0, 1,
ext::oneapi::detail::default_reduction_algorithm<
false, access::placeholder::true_t, 1>>>
reduction(buffer<T, 1, AllocatorT> Var, handler &CGH, BinaryOperation,
const property_list &PropList = {}) {
bool InitializeToIdentity =
Expand All @@ -35,7 +37,9 @@ reduction(buffer<T, 1, AllocatorT> Var, handler &CGH, BinaryOperation,
template <typename T, typename AllocatorT, typename BinaryOperation>
std::enable_if_t<!has_known_identity<BinaryOperation, T>::value,
ext::oneapi::detail::reduction_impl<
T, BinaryOperation, 1, false, access::placeholder::true_t>>
T, BinaryOperation, 0, 1,
ext::oneapi::detail::default_reduction_algorithm<
false, access::placeholder::true_t, 1>>>
reduction(buffer<T, 1, AllocatorT>, handler &, BinaryOperation,
const property_list &PropList = {}) {
// TODO: implement reduction that works even when identity is not known.
Expand All @@ -49,9 +53,11 @@ reduction(buffer<T, 1, AllocatorT>, handler &, BinaryOperation,
/// the given USM pointer \p Var, handler \p CGH, reduction operation
/// \p Combiner, and optional reduction properties.
template <typename T, typename BinaryOperation>
std::enable_if_t<
has_known_identity<BinaryOperation, T>::value,
ext::oneapi::detail::reduction_impl<T, BinaryOperation, 1, true>>
std::enable_if_t<has_known_identity<BinaryOperation, T>::value,
ext::oneapi::detail::reduction_impl<
T, BinaryOperation, 0, 1,
ext::oneapi::detail::default_reduction_algorithm<
true, access::placeholder::false_t, 1>>>
reduction(T *Var, BinaryOperation, const property_list &PropList = {}) {
bool InitializeToIdentity =
PropList.has_property<property::reduction::initialize_to_identity>();
Expand All @@ -64,9 +70,11 @@ reduction(T *Var, BinaryOperation, const property_list &PropList = {}) {
/// The reduction algorithm may be less efficient for this variant as the
/// reduction identity is not known statically and it is not provided by user.
template <typename T, typename BinaryOperation>
std::enable_if_t<
!has_known_identity<BinaryOperation, T>::value,
ext::oneapi::detail::reduction_impl<T, BinaryOperation, 1, true>>
std::enable_if_t<!has_known_identity<BinaryOperation, T>::value,
ext::oneapi::detail::reduction_impl<
T, BinaryOperation, 0, 1,
ext::oneapi::detail::default_reduction_algorithm<
true, access::placeholder::false_t, 1>>>
reduction(T *, BinaryOperation, const property_list &PropList = {}) {
// TODO: implement reduction that works even when identity is not known.
(void)PropList;
Expand All @@ -79,8 +87,10 @@ reduction(T *, BinaryOperation, const property_list &PropList = {}) {
/// reduction identity value \p Identity, reduction operation \p Combiner,
/// and optional reduction properties.
template <typename T, typename AllocatorT, typename BinaryOperation>
ext::oneapi::detail::reduction_impl<T, BinaryOperation, 1, false,
access::placeholder::true_t>
ext::oneapi::detail::reduction_impl<
T, BinaryOperation, 0, 1,
ext::oneapi::detail::default_reduction_algorithm<
false, access::placeholder::true_t, 1>>
reduction(buffer<T, 1, AllocatorT> Var, handler &CGH, const T &Identity,
BinaryOperation Combiner, const property_list &PropList = {}) {
bool InitializeToIdentity =
Expand All @@ -92,13 +102,72 @@ reduction(buffer<T, 1, AllocatorT> Var, handler &CGH, const T &Identity,
/// the given USM pointer \p Var, reduction identity value \p Identity,
/// binary operation \p Combiner, and optional reduction properties.
template <typename T, typename BinaryOperation>
ext::oneapi::detail::reduction_impl<T, BinaryOperation, 1, true>
ext::oneapi::detail::reduction_impl<
T, BinaryOperation, 0, 1,
ext::oneapi::detail::default_reduction_algorithm<
true, access::placeholder::false_t, 1>>
reduction(T *Var, const T &Identity, BinaryOperation Combiner,
const property_list &PropList = {}) {
bool InitializeToIdentity =
PropList.has_property<property::reduction::initialize_to_identity>();
return {Var, Identity, Combiner, InitializeToIdentity};
}

#if __cplusplus >= 201703L
/// Constructs a reduction object using the reduction variable referenced by
/// the given sycl::span \p Span, reduction operation \p Combiner, and
/// optional reduction properties.
template <typename T, size_t Extent, typename BinaryOperation>
std::enable_if_t<Extent != dynamic_extent &&
has_known_identity<BinaryOperation, T>::value,
ext::oneapi::detail::reduction_impl<
T, BinaryOperation, 1, Extent,
ext::oneapi::detail::default_reduction_algorithm<
true, access::placeholder::false_t, 1>>>
reduction(span<T, Extent> Span, BinaryOperation,
const property_list &PropList = {}) {
bool InitializeToIdentity =
PropList.has_property<property::reduction::initialize_to_identity>();
return {Span, InitializeToIdentity};
}

/// Constructs a reduction object using the reduction variable referenced by
/// the given sycl::span \p Span, reduction operation \p Combiner, and
/// optional reduction properties.
/// The reduction algorithm may be less efficient for this variant as the
/// reduction identity is not known statically and it is not provided by user.
template <typename T, size_t Extent, typename BinaryOperation>
std::enable_if_t<Extent != dynamic_extent &&
!has_known_identity<BinaryOperation, T>::value,
ext::oneapi::detail::reduction_impl<
T, BinaryOperation, 1, Extent,
ext::oneapi::detail::default_reduction_algorithm<
true, access::placeholder::false_t, 1>>>
reduction(span<T, Extent> Span, BinaryOperation,
const property_list &PropList = {}) {
// TODO: implement reduction that works even when identity is not known.
(void)PropList;
throw runtime_error("Identity-less reductions with unknown identity are not "
"supported yet.",
PI_INVALID_VALUE);
}

/// Constructs a reduction object using the reduction variable referenced by
/// the given sycl::span \p Span, reduction identity value \p Identity,
/// reduction operation \p Combiner, and optional reduction properties.
template <typename T, size_t Extent, typename BinaryOperation>
std::enable_if_t<Extent != dynamic_extent,
ext::oneapi::detail::reduction_impl<
T, BinaryOperation, 1, Extent,
ext::oneapi::detail::default_reduction_algorithm<
true, access::placeholder::false_t, 1>>>
reduction(span<T, Extent> Span, const T &Identity, BinaryOperation Combiner,
const property_list &PropList = {}) {
bool InitializeToIdentity =
PropList.has_property<property::reduction::initialize_to_identity>();
return {Span, Identity, Combiner, InitializeToIdentity};
}
#endif

} // namespace sycl
} // __SYCL_INLINE_NAMESPACE(cl)
Loading

0 comments on commit 863383b

Please sign in to comment.