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[CUB] Make ReduceByKey run-to-run deterministic #11032
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| Original file line number | Diff line number | Diff line change |
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@@ -112,6 +112,14 @@ struct streaming_context | |
| } | ||
| }; | ||
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| // Bind the stability flag while selecting the default and fallback agent policies. | ||
| template <bool StableReductionOrder, typename Policy, typename... Args> | ||
| using vsmem_helper_t = | ||
| vsmem_helper_with_fallback_impl<Policy, | ||
| AgentReduceByKey<Policy, StableReductionOrder, Args...>, | ||
| policy_wrapper_t<Policy, 64, 1>, | ||
| AgentReduceByKey<policy_wrapper_t<Policy, 64, 1>, StableReductionOrder, Args...>>; | ||
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| /** | ||
| * @brief Multi-block reduce-by-key sweep kernel entry point | ||
| * | ||
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@@ -145,6 +153,9 @@ struct streaming_context | |
| * @tparam OffsetT | ||
| * Signed integer type for global offsets | ||
| * | ||
| * @tparam StableReductionOrder | ||
| * Whether to use a stable reduction order across tiles | ||
| * | ||
| * @param d_keys_in | ||
| * Pointer to the input sequence of keys | ||
| * | ||
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@@ -187,7 +198,8 @@ template <typename PolicySelector, | |
| typename ReductionOpT, | ||
| typename OffsetT, | ||
| typename AccumT, | ||
| typename StreamingContextT, | ||
| bool StableReductionOrder> | ||
| #if _CCCL_HAS_CONCEPTS() | ||
| requires reduce_by_key_policy_selector<PolicySelector> | ||
| #endif | ||
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@@ -217,9 +229,9 @@ __launch_bounds__(int(current_policy<PolicySelector>().lookback.threads_per_bloc | |
| policy.lookback.lookback_delay.delay, | ||
| policy.lookback.lookback_delay.l2_write_latency>>; | ||
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| using vsmem_helper_t = reduce_by_key::vsmem_helper_t< | ||
| StableReductionOrder, | ||
| AgentReduceByKeyPolicyT, | ||
| KeysInputIteratorT, | ||
| UniqueOutputIteratorT, | ||
| ValuesInputIteratorT, | ||
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@@ -374,9 +386,9 @@ struct CCCL_DEPRECATED_BECAUSE("Use the tuning API for DeviceReduce::ReduceByKey | |
| CUB_RUNTIME_FUNCTION _CCCL_VISIBILITY_HIDDEN _CCCL_FORCEINLINE cudaError_t | ||
| Invoke(ScanInitKernelT init_kernel, ReduceByKeyKernelT reduce_by_key_kernel) | ||
| { | ||
| using vsmem_helper_t = detail::reduce_by_key::vsmem_helper_t< | ||
| false, | ||
|
Contributor
There was a problem hiding this comment. Q: why are we passing
Contributor
Author
There was a problem hiding this comment. this is the deprecated dispatcher, which has no
Contributor
There was a problem hiding this comment. @ahmedtaha100 please use an inline comment to indicate the name of the template parameter |
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| typename ActivePolicyT::ReduceByKeyPolicyT, | ||
| KeysInputIteratorT, | ||
| UniqueOutputIteratorT, | ||
| ValuesInputIteratorT, | ||
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@@ -555,7 +567,8 @@ struct CCCL_DEPRECATED_BECAUSE("Use the tuning API for DeviceReduce::ReduceByKey | |
| ReductionOpT, | ||
| OffsetT, | ||
| AccumT, | ||
| streaming_context_t, | ||
| false>); | ||
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| } | ||
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| /** | ||
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@@ -650,7 +663,7 @@ struct CCCL_DEPRECATED_BECAUSE("Use the tuning API for DeviceReduce::ReduceByKey | |
| namespace detail::reduce_by_key | ||
| { | ||
| // we move the conversion of the policy to the agent policy and its use out of the lambda below, so MSVC does not ICE | ||
| template <bool StableReductionOrder, typename PolicyGetter, typename... Args> | ||
| _CCCL_HOST_DEVICE_API auto determine_threads_items_vsmem(PolicyGetter policy_getter) | ||
| { | ||
| // TODO(bgruber): refactor this in the future | ||
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@@ -664,13 +677,14 @@ _CCCL_HOST_DEVICE_API auto determine_threads_items_vsmem(PolicyGetter policy_get | |
| delay_constructor_t<policy.lookback.lookback_delay.kind, | ||
| policy.lookback.lookback_delay.delay, | ||
| policy.lookback.lookback_delay.l2_write_latency>>; | ||
| using vsmem_helper_t = reduce_by_key::vsmem_helper_t<StableReductionOrder, Policy, Args...>; | ||
| return ::cuda::std::tuple{vsmem_helper_t::agent_policy_t::BLOCK_THREADS, | ||
| vsmem_helper_t::agent_policy_t::ITEMS_PER_THREAD, | ||
| vsmem_helper_t::vsmem_per_block}; | ||
| } | ||
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| template <bool StableReductionOrder, | ||
| typename KeysInputIteratorT, | ||
| typename UniqueOutputIteratorT, | ||
| typename ValuesInputIteratorT, | ||
| typename AggregatesOutputIteratorT, | ||
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@@ -721,6 +735,7 @@ CUB_RUNTIME_FUNCTION _CCCL_FORCEINLINE static cudaError_t dispatch( | |
| #endif // _CCCL_HOSTED() && defined(CUB_DEBUG_LOG) | ||
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| const auto [threads_per_block, items_per_thread, vsmem_per_block] = determine_threads_items_vsmem< | ||
| StableReductionOrder, | ||
| decltype(policy_getter), | ||
| KeysInputIteratorT, | ||
| UniqueOutputIteratorT, | ||
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@@ -799,7 +814,8 @@ CUB_RUNTIME_FUNCTION _CCCL_FORCEINLINE static cudaError_t dispatch( | |
| ReductionOpT, | ||
| OffsetT, | ||
| AccumT, | ||
| streaming_context_t, | ||
| StableReductionOrder>; | ||
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| int reduce_by_key_sm_occupancy{}; | ||
| if (const auto error = | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -111,9 +111,9 @@ __launch_bounds__(int(current_policy<PolicySelector>().lookback.threads_per_bloc | |
| policy.lookback.lookback_delay.delay, | ||
| policy.lookback.lookback_delay.l2_write_latency>>; | ||
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| using vsmem_helper_t = reduce_by_key::vsmem_helper_t< | ||
| false, | ||
| AgentReduceByKeyPolicyT, | ||
| KeysInputIteratorT, | ||
| UniqueOutputIteratorT, | ||
| ValuesInputIteratorT, | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -36,7 +36,7 @@ struct reduce_by_key_kernel_source | |
| template <typename PolicySelector, typename... KernelArgTs> | ||
| [[nodiscard]] CUB_RUNTIME_FUNCTION static constexpr auto reduce_by_key_kernel() | ||
| { | ||
| return &DeviceReduceByKeyKernel<PolicySelector, KernelArgTs..., false>; | ||
| } | ||
| }; | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -5,6 +5,9 @@ | |
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| #include <cub/device/device_reduce.cuh> | ||
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| #include <cuda/std/__bit/bit_cast.h> | ||
| #include <cuda/std/__functional/operations.h> | ||
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| #include "catch2_test_device_reduce.cuh" | ||
| #include "catch2_test_launch_helper.h" | ||
| #include "cub_test_macros.h" | ||
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@@ -156,3 +159,89 @@ CUB_TEST("Device reduce-by-key works", "[by_key][reduce][device]", CUB_SMALL, fu | |
| REQUIRE(expected_keys == out_unique_keys); | ||
| } | ||
| } | ||
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| #if TEST_LAUNCH == 0 && TEST_TYPES == 0 | ||
| CUB_TEST_CASE("Device reduce-by-key is run-to-run deterministic for fp64 sums", "[by_key][reduce][device]", CUB_SMALL) | ||
| { | ||
| // Span several waves of tiles so that the unfixed lookback grouping can vary on large GPUs. | ||
| constexpr int num_items = 262'144; | ||
| constexpr int long_run = 200'000; | ||
| constexpr int short_run = 64; | ||
| constexpr int num_repetitions = 20; | ||
| constexpr int num_runs = 1 + (num_items - long_run + short_run - 1) / short_run; | ||
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| c2h::host_vector<std::uint64_t> keys(num_items); | ||
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| for (int i = 0; i < num_items; ++i) | ||
| { | ||
| keys[i] = i < long_run ? 0 : 1 + (i - long_run) / short_run; | ||
| } | ||
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| c2h::device_vector<std::uint64_t> keys_in = keys; | ||
| c2h::device_vector<double> values_in(num_items); | ||
| c2h::gen(C2H_SEED(2), values_in, -1e-2, 1e-2); | ||
| c2h::device_vector<std::uint64_t> unique_out(num_runs); | ||
| c2h::device_vector<double> aggregates_out(num_runs); | ||
| c2h::device_vector<int> num_runs_out(1); | ||
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| const auto d_keys_in = thrust::raw_pointer_cast(keys_in.data()); | ||
| const auto d_values_in = thrust::raw_pointer_cast(values_in.data()); | ||
| const auto d_unique_out = thrust::raw_pointer_cast(unique_out.data()); | ||
| const auto d_aggregates_out = thrust::raw_pointer_cast(aggregates_out.data()); | ||
| const auto d_num_runs_out = thrust::raw_pointer_cast(num_runs_out.data()); | ||
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| std::size_t temp_storage_bytes{}; | ||
| REQUIRE( | ||
| cudaSuccess | ||
| == cub::DeviceReduce::ReduceByKey( | ||
| nullptr, | ||
| temp_storage_bytes, | ||
| d_keys_in, | ||
| d_unique_out, | ||
| d_values_in, | ||
| d_aggregates_out, | ||
| d_num_runs_out, | ||
| cuda::std::plus{}, | ||
| num_items)); | ||
| c2h::device_vector<std::uint8_t> temp_storage(temp_storage_bytes, thrust::no_init); | ||
| const auto d_temp_storage = thrust::raw_pointer_cast(temp_storage.data()); | ||
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| c2h::host_vector<std::uint64_t> expected_keys; | ||
| c2h::host_vector<std::uint64_t> expected_aggregates; | ||
| for (int repetition = 0; repetition < num_repetitions; ++repetition) | ||
| { | ||
| REQUIRE(cudaSuccess == cudaMemset(d_aggregates_out, 0xee, num_runs * sizeof(double))); | ||
| REQUIRE( | ||
| cudaSuccess | ||
| == cub::DeviceReduce::ReduceByKey( | ||
| d_temp_storage, | ||
| temp_storage_bytes, | ||
| d_keys_in, | ||
| d_unique_out, | ||
| d_values_in, | ||
| d_aggregates_out, | ||
| d_num_runs_out, | ||
| cuda::std::plus{}, | ||
| num_items)); | ||
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| REQUIRE(num_runs_out[0] == num_runs); | ||
| const c2h::host_vector<std::uint64_t> result_keys = unique_out; | ||
| const c2h::host_vector<double> result_aggregates = aggregates_out; | ||
| c2h::host_vector<std::uint64_t> result_bits(num_runs); | ||
| for (int run = 0; run < num_runs; ++run) | ||
| { | ||
| result_bits[run] = cuda::std::bit_cast<std::uint64_t>(result_aggregates[run]); | ||
| } | ||
| if (repetition == 0) | ||
| { | ||
| expected_keys = result_keys; | ||
| expected_aggregates = result_bits; | ||
| } | ||
| else | ||
| { | ||
| REQUIRE(result_keys == expected_keys); | ||
| REQUIRE(result_bits == expected_aggregates); | ||
| } | ||
| } | ||
| } | ||
| #endif // TEST_LAUNCH == 0 && TEST_TYPES == 0 | ||
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Nit: let's please keep the ordering of the template parameters consistent, so this should go at the end of the template parameter list