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CUDA: Limit DeviceSegmentedSort to immediate mode #21718

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ORippler merged 2 commits into from
Apr 13, 2026
+57 −23
Merged

CUDA: Limit DeviceSegmentedSort to immediate mode #21718

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51a86d5
CUDA: Limit DeviceSegmentedSort to immediate mode
ORippler Apr 10, 2026
c8f82b0
Add test case for dispatch to DeviceSegmentedRadixSort
ORippler Apr 10, 2026
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79 changes: 56 additions & 23 deletions ggml/src/ggml-cuda/argsort.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -58,26 +58,48 @@ void argsort_f32_i32_cuda_cub(ggml_cuda_pool & pool,

size_t temp_storage_bytes = 0;

bool is_capturing = false;
#ifdef USE_CUDA_GRAPH
// Currently (confirmed for CCCL <= 3.2) DeviceSegmentedSort does not support stream capture, while DeviceSegmentedRadixSort does.
// See https://github.com/NVIDIA/cccl/issues/5661#issuecomment-3229037149
// TODO: constrain this to the CCCL versions that have this issue once it's resolved in a future CCCL release.
cudaStreamCaptureStatus capture_status;
CUDA_CHECK(cudaStreamIsCapturing(stream, &capture_status));
is_capturing = (capture_status != cudaStreamCaptureStatusNone);
#endif // USE_CUDA_GRAPH

if (order == GGML_SORT_ORDER_ASC) {
if (nrows == 1) {
CUDA_CHECK(DeviceRadixSort::SortPairs(nullptr, temp_storage_bytes, temp_keys, temp_keys, // keys (in-place)
temp_indices, dst, // values (indices)
ncols, 0, sizeof(float) * 8, stream));
temp_indices, dst, // values (indices)
ncols, 0, sizeof(float) * 8, stream));
} else if (is_capturing) {
CUDA_CHECK(DeviceSegmentedRadixSort::SortPairs(
nullptr, temp_storage_bytes, temp_keys, temp_keys, // keys (in-place)
temp_indices, dst, // values (indices)
ncols * nrows, nrows, // num items, num segments
offset_iterator, offset_iterator + 1, 0, sizeof(float) * 8, stream));
} else {
CUDA_CHECK(DeviceSegmentedSort::SortPairs(nullptr, temp_storage_bytes, temp_keys, temp_keys, // keys (in-place)
temp_indices, dst, // values (indices)
ncols * nrows, nrows, // num items, num segments
offset_iterator, offset_iterator + 1, stream));
CUDA_CHECK(DeviceSegmentedSort::SortPairs(nullptr, temp_storage_bytes, temp_keys,
temp_keys, // keys (in-place)
temp_indices, dst, // values (indices)
ncols * nrows, nrows, // num items, num segments
offset_iterator, offset_iterator + 1, stream));
}
} else {
if (nrows == 1) {
CUDA_CHECK(DeviceRadixSort::SortPairsDescending(nullptr, temp_storage_bytes, temp_keys, temp_keys, // keys (in-place)
temp_indices, dst, // values (indices)
ncols, 0, sizeof(float) * 8, stream));
CUDA_CHECK(DeviceRadixSort::SortPairsDescending(nullptr, temp_storage_bytes, temp_keys,
temp_keys, // keys (in-place)
temp_indices, dst, // values (indices)
ncols, 0, sizeof(float) * 8, stream));
} else if (is_capturing) {
CUDA_CHECK(DeviceSegmentedRadixSort::SortPairsDescending(
nullptr, temp_storage_bytes, temp_keys, temp_keys, temp_indices, dst, ncols * nrows, nrows,
offset_iterator, offset_iterator + 1, 0, sizeof(float) * 8, stream));
} else {
CUDA_CHECK(DeviceSegmentedSort::SortPairsDescending(nullptr, temp_storage_bytes, temp_keys, temp_keys, temp_indices,
dst, ncols * nrows, nrows, offset_iterator, offset_iterator + 1,
stream));
CUDA_CHECK(DeviceSegmentedSort::SortPairsDescending(nullptr, temp_storage_bytes, temp_keys, temp_keys,
temp_indices, dst, ncols * nrows, nrows,
offset_iterator, offset_iterator + 1, stream));
}
}

Expand All @@ -86,22 +108,33 @@ void argsort_f32_i32_cuda_cub(ggml_cuda_pool & pool,

if (order == GGML_SORT_ORDER_ASC) {
if (nrows == 1) {
CUDA_CHECK(DeviceRadixSort::SortPairs(d_temp_storage, temp_storage_bytes, temp_keys, temp_keys, // keys (in-place)
temp_indices, dst, // values (indices)
ncols, 0, sizeof(float) * 8, stream));
CUDA_CHECK(DeviceRadixSort::SortPairs(d_temp_storage, temp_storage_bytes, temp_keys,
temp_keys, // keys (in-place)
temp_indices, dst, // values (indices)
ncols, 0, sizeof(float) * 8, stream));
} else if (is_capturing) {
CUDA_CHECK(DeviceSegmentedRadixSort::SortPairs(d_temp_storage, temp_storage_bytes, temp_keys, temp_keys,
temp_indices, dst, ncols * nrows, nrows, offset_iterator,
offset_iterator + 1, 0, sizeof(float) * 8, stream));
} else {
CUDA_CHECK(DeviceSegmentedSort::SortPairs(d_temp_storage, temp_storage_bytes, temp_keys, temp_keys, temp_indices, dst,
ncols * nrows, nrows, offset_iterator, offset_iterator + 1, stream));
CUDA_CHECK(DeviceSegmentedSort::SortPairs(d_temp_storage, temp_storage_bytes, temp_keys, temp_keys,
temp_indices, dst, ncols * nrows, nrows, offset_iterator,
offset_iterator + 1, stream));
}
} else {
if (nrows == 1) {
CUDA_CHECK(DeviceRadixSort::SortPairsDescending(d_temp_storage, temp_storage_bytes, temp_keys, temp_keys, // keys (in-place)
temp_indices, dst, // values (indices)
ncols, 0, sizeof(float) * 8, stream));
CUDA_CHECK(DeviceRadixSort::SortPairsDescending(d_temp_storage, temp_storage_bytes, temp_keys,
temp_keys, // keys (in-place)
temp_indices, dst, // values (indices)
ncols, 0, sizeof(float) * 8, stream));
} else if (is_capturing) {
CUDA_CHECK(DeviceSegmentedRadixSort::SortPairsDescending(
d_temp_storage, temp_storage_bytes, temp_keys, temp_keys, temp_indices, dst, ncols * nrows, nrows,
offset_iterator, offset_iterator + 1, 0, sizeof(float) * 8, stream));
} else {
CUDA_CHECK(DeviceSegmentedSort::SortPairsDescending(d_temp_storage, temp_storage_bytes, temp_keys, temp_keys,
temp_indices, dst, ncols * nrows, nrows, offset_iterator,
offset_iterator + 1, stream));
CUDA_CHECK(DeviceSegmentedSort::SortPairsDescending(d_temp_storage, temp_storage_bytes, temp_keys,
temp_keys, temp_indices, dst, ncols * nrows, nrows,
offset_iterator, offset_iterator + 1, stream));
}
}
}
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1 change: 1 addition & 0 deletions tests/test-backend-ops.cpp
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Expand Up @@ -8397,6 +8397,7 @@ static std::vector<std::unique_ptr<test_case>> make_test_cases_eval() {
test_cases.emplace_back(new test_argsort(GGML_TYPE_F32, {2048, 2, 1, 3}, order));
test_cases.emplace_back(new test_argsort(GGML_TYPE_F32, {2049, 2, 1, 3}, order));
test_cases.emplace_back(new test_argsort(GGML_TYPE_F32, {2, 8, 8192, 1}, order)); // bailingmoe2 (group selection)
test_cases.emplace_back(new test_argsort(GGML_TYPE_F32, {2048, 512, 1, 1}, order)); // test CUDA dispatching to radix sort for nrows > = 1 in graph mode
}

for (int n = 1; n < 5; ++n) {
Expand Down
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