Avoid extra loops on sorted data in the __subgroup_bubble_sorter::sort
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….h - fix corner case performance issue in the __subgroup_bubble_sorter::sort Signed-off-by: Sergey Kopienko <[email protected]>
….h - avoid loops and condition checks for small data sizes in __subgroup_bubble_sorter::sort Signed-off-by: Sergey Kopienko <[email protected]>
SergeyKopienko
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Sep 24, 2024
include/oneapi/dpl/pstl/hetero/dpcpp/parallel_backend_sycl_merge_sort.h
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| _IndexType __n = __end - __start; | ||
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| switch (__n) |
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There are no other occurrences of switch in the library. What about using if-else? I guess switch is not necessary here due to having only 4 options.
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I believe switch / case should works faster.
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For large number of elements switch should perform better although I do not know in device code. However, with just 4 cases there's probably no difference.
In my opinion, unless there is a measurable performance difference between switch and if-else, then we should use if-else.
include/oneapi/dpl/pstl/hetero/dpcpp/parallel_backend_sycl_merge_sort.h
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include/oneapi/dpl/pstl/hetero/dpcpp/parallel_backend_sycl_merge_sort.h
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mmichel11
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Sep 24, 2024
….h - fix review comment: allow ADL as it was originally Signed-off-by: Sergey Kopienko <[email protected]>
….h - fix review comment: the overflow is handled in the caller side, so it does not make sense to make a signed type. Signed-off-by: Sergey Kopienko <[email protected]>
….h - fix review comment: additional comments Signed-off-by: Sergey Kopienko <[email protected]>
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SergeyKopienko
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Sep 25, 2024
| if (__comp(__second_item, __first_item)) | ||
| { | ||
| using std::swap; | ||
| swap(__first_item, __second_item); | ||
| } | ||
| } | ||
| break; | ||
| default: // The case when __end > __start + 2 three or more source data items require full bubble sort | ||
| do |
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Implementation from https://en.wikipedia.org/wiki/Bubble_sort
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In this PR we avoid extra loops on sorted data in the
__subgroup_bubble_sorter::sort,which calls in sort algorithms on the device for every work item.
This is beneficial when the data is already sorted, which according to https://en.wikipedia.org/wiki/Sorting_algorithm is a common real-world case.