Avoid extra loops on sorted data in the __subgroup_bubble_sorter::sort
#1874
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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
commented
Sep 24, 2024
| case 0: | ||
| case 1: | ||
| break; | ||
| case 2: |
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I propose to ignore clang format at this place.
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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.
| if (__comp(__second_item, __first_item)) | ||
| std::swap(__first_item, __second_item); |
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Could you allow ADL as it was originally?
using std::swap;
swap(__first_item, __second_item);
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| using _IndexType = std::make_signed_t<decltype(__end)>; | ||
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| _IndexType __n = __end - __start; |
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The overflow is handled in the caller side, so it does not make sense to make a signed type. Also, it makes the positive range of data smaller, which may result in warnings (I do not expect it overflow, though).
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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.