Skip to content

[CUB] Fix DeviceAdjacentDifference for cuda::device_buffer iterators #9861

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
Noperi0r wants to merge 4 commits into
base: main
Choose a base branch
from
+18 −1
Open

[CUB] Fix DeviceAdjacentDifference for cuda::device_buffer iterators #9861

Show file tree
Hide file tree
Changes from 3 commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
1b058db
Fix DeviceAdjacentDifference for device_buffer iterators [skip-docs]
Noperi0r Jul 14, 2026
facc0d5
Move DeviceAdjacentDifference device_buffer test [skip-docs]
Noperi0r Jul 15, 2026
7aed3a4
Make AdjacentDifference output pointer binding const [skip-docs]
Noperi0r Jul 15, 2026
8c1fa4f
Use launch wrapper in device_buffer regression test [skip-docs]
Noperi0r Jul 15, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion cub/cub/agent/agent_adjacent_difference.cuh
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -105,7 +105,7 @@ struct AgentDifference
OffsetT num_items)
: temp_storage(temp_storage.Alias())
, input_it(input_it)
, load_it(LoadIt(input_it))
, load_it(try_make_cache_modified_iterator<Policy::LOAD_MODIFIER>(input_it))
, first_tile_previous(first_tile_previous)
, result(result)
, difference_op(difference_op)
Expand Down
30 changes: 30 additions & 0 deletions cub/test/catch2_test_device_adjacent_difference_substract_left.cu
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@

#include <cub/device/device_adjacent_difference.cuh>

#include <cuda/buffer>
#include <cuda/devices>
#include <cuda/iterator>
#include <cuda/std/execution>
Expand Down Expand Up @@ -258,6 +259,35 @@ C2H_TEST("DeviceAdjacentDifference::SubtractLeftCopy works with user provided me
test_subtract_left_copy(policy);
}
}

C2H_TEST("DeviceAdjacentDifference::SubtractLeftCopy accepts cuda::device_buffer input",
"[adjacent_difference][device]")
{
using type = std::int32_t;

cuda::stream stream{cuda::devices[0]};
auto input = cuda::make_device_buffer<type>(stream, cuda::devices[0], {2, 5, 9, 14, 20});
c2h::device_vector<type> output(input.size(), thrust::no_init);
const auto output_it = thrust::raw_pointer_cast(output.data());

void* temporary_storage = nullptr;
std::size_t temporary_bytes = 0;
REQUIRE(
cudaSuccess
== cub::DeviceAdjacentDifference::SubtractLeftCopy(
temporary_storage, temporary_bytes, input.begin(), output_it, input.size(), cuda::std::minus<>{}, stream.get()));

c2h::device_vector<std::uint8_t> temporary_buffer(temporary_bytes, thrust::no_init);
temporary_storage = thrust::raw_pointer_cast(temporary_buffer.data());
REQUIRE(
cudaSuccess
== cub::DeviceAdjacentDifference::SubtractLeftCopy(
temporary_storage, temporary_bytes, input.begin(), output_it, input.size(), cuda::std::minus<>{}, stream.get()));

@bernhardmgruber bernhardmgruber Jul 15, 2026

Copy link
Copy Markdown
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Important: Just use the launch wrapper adjacent_difference_subtract_left instead of handling the temporary storage allocation yourself.

@Noperi0r Noperi0r Jul 15, 2026

Copy link
Copy Markdown
Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Updated the regression test to use adjacent_difference_subtract_left_copy, since this test covers SubtractLeftCopy. The launch wrapper now handles the temporary storage internally.

The focused target build, regression test, and targeted pre-commit checks pass locally.

stream.sync();

const c2h::host_vector<type> expected{2, 3, 4, 5, 6};
REQUIRE(output == expected);
Comment on lines +274 to +276

@bernhardmgruber bernhardmgruber Jul 15, 2026

Copy link
Copy Markdown
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Important: I think we do not to sync when we use a custom stream:

Suggested change
const c2h::host_vector<type> expected{2, 3, 4, 5, 6};
REQUIRE(output == expected);
stream.sync();
const c2h::host_vector<type> expected{2, 3, 4, 5, 6};
REQUIRE(output == expected);

}
#endif // TEST_LAUNCH == 0

C2H_TEST("DeviceAdjacentDifference::SubtractLeftCopy works with iterators", "[device][adjacent_difference]", types)
Expand Down