pitrou commented on code in PR #45763: URL: https://github.com/apache/arrow/pull/45763#discussion_r1998397990
########## cpp/src/arrow/compute/kernels/vector_statistics.cc: ########## @@ -0,0 +1,208 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +#include <functional> +#include <memory> +#include <optional> +#include <utility> + +#include "arrow/compute/api_aggregate.h" +#include "arrow/compute/api_vector.h" +#include "arrow/compute/exec.h" +#include "arrow/compute/function.h" +#include "arrow/compute/kernel.h" +#include "arrow/compute/kernels/codegen_internal.h" +#include "arrow/compute/registry.h" +#include "arrow/result.h" +#include "arrow/scalar.h" +#include "arrow/status.h" +#include "arrow/util/bit_run_reader.h" +#include "arrow/util/checked_cast.h" +#include "arrow/util/logging.h" + +namespace arrow::compute::internal { + +using ::arrow::internal::checked_cast; + +namespace { + +Status ValidateOptions(const WinsorizeOptions& options) { + if (!(options.lower_limit >= 0 && options.lower_limit <= 1) || + !(options.upper_limit >= 0 && options.upper_limit <= 1)) { + return Status::Invalid("winsorize limits must be between 0 and 1"); + } + if (options.lower_limit > options.upper_limit) { + return Status::Invalid( + "winsorize upper limit must be equal or greater than lower limit"); + } + return Status::OK(); +} + +using WinsorizeState = internal::OptionsWrapper<WinsorizeOptions>; + +// We have a first unused template parameter for compatibility with GenerateNumeric. +template <typename Unused, typename Type> +struct Winsorize { + using ArrayType = typename TypeTraits<Type>::ArrayType; + using CType = typename TypeTraits<Type>::CType; + + static Status Exec(KernelContext* ctx, const ExecSpan& batch, ExecResult* out) { + const auto& options = WinsorizeState::Get(ctx); + RETURN_NOT_OK(ValidateOptions(options)); + ARROW_ASSIGN_OR_RAISE(auto maybe_quantiles, + GetQuantileValues(ctx, batch.ToExecBatch(), options)); + auto data = batch.values[0].array.ToArrayData(); + auto out_data = out->array_data_mutable(); + if (!maybe_quantiles.has_value()) { + // Only nulls and NaNs => return input as-is + out_data->null_count = data->null_count.load(); + out_data->length = data->length; + out_data->buffers = data->buffers; + return Status::OK(); + } + return ClipValues(*data, maybe_quantiles.value(), out_data, ctx); + } + + static Status ExecChunked(KernelContext* ctx, const ExecBatch& batch, Datum* out) { + const auto& options = WinsorizeState::Get(ctx); + RETURN_NOT_OK(ValidateOptions(options)); + ARROW_ASSIGN_OR_RAISE(auto maybe_quantiles, GetQuantileValues(ctx, batch, options)); + const auto& chunked_array = batch.values[0].chunked_array(); + if (!maybe_quantiles.has_value()) { + // Only nulls and NaNs => return input as-is + *out = chunked_array; + return Status::OK(); + } + ArrayVector out_chunks; + out_chunks.reserve(chunked_array->num_chunks()); + for (const auto& chunk : chunked_array->chunks()) { + auto out_data = chunk->data()->Copy(); + RETURN_NOT_OK( + ClipValues(*chunk->data(), maybe_quantiles.value(), out_data.get(), ctx)); + out_chunks.push_back(MakeArray(out_data)); + } + return ChunkedArray::Make(std::move(out_chunks)).Value(out); + } + + struct QuantileValues { + CType lower_bound, upper_bound; + }; + + static Result<std::optional<QuantileValues>> GetQuantileValues( + KernelContext* ctx, const ExecBatch& batch, const WinsorizeOptions& options) { + // We use "nearest" to avoid the conversion of quantile values to double. + QuantileOptions quantile_options(/*q=*/{options.lower_limit, options.upper_limit}, + QuantileOptions::NEAREST); + ARROW_ASSIGN_OR_RAISE( + auto quantile, + CallFunction("quantile", batch, &quantile_options, ctx->exec_context())); + auto quantile_array = quantile.array_as<ArrayType>(); + DCHECK_EQ(quantile_array->length(), 2); + if (quantile_array->null_count() == 2) { + return std::nullopt; + } + DCHECK_EQ(quantile_array->null_count(), 0); + return QuantileValues{CType(quantile_array->Value(0)), + CType(quantile_array->Value(1))}; + } + + static Status ClipValues(const ArrayData& data, QuantileValues quantiles, + ArrayData* out, KernelContext* ctx) { + DCHECK_EQ(out->buffers.size(), data.buffers.size()); + out->null_count = data.null_count.load(); + out->length = data.length; + out->buffers[0] = data.buffers[0]; + ARROW_ASSIGN_OR_RAISE(out->buffers[1], ctx->Allocate(out->length * sizeof(CType))); + // Avoid leaving uninitialized memory under null entries + std::memset(out->buffers[1]->mutable_data(), 0, out->length * sizeof(CType)); + + const CType* in_values = data.GetValues<CType>(1); + CType* out_values = out->GetMutableValues<CType>(1); + + auto visit = [&](int64_t position, int64_t length) { + for (int64_t i = position; i < position + length; ++i) { + if (in_values[i] < quantiles.lower_bound) { + out_values[i] = quantiles.lower_bound; + } else if (in_values[i] > quantiles.upper_bound) { + out_values[i] = quantiles.upper_bound; + } else { + // NaNs also fall here + out_values[i] = in_values[i]; + } + } + }; + arrow::internal::VisitSetBitRunsVoid(data.buffers[0], data.offset, data.length, + visit); + return Status::OK(); + } +}; + +template <typename Unused, typename Type> +struct WinsorizeChunked { + static Status Exec(KernelContext* ctx, const ExecBatch& batch, Datum* out) { + return Winsorize<Unused, Type>::ExecChunked(ctx, batch, out); + } +}; + +Result<TypeHolder> ResolveWinsorizeOutput(KernelContext* ctx, + const std::vector<TypeHolder>& in_types) { + DCHECK_EQ(in_types.size(), 1); + return in_types[0]; +} + +const FunctionDoc winsorize_doc( + "Winsorize an array", + ("This function applies a winsorization transform to the input array\n" + "so as to reduce the influence of potential outliers.\n" + "NaNs and nulls in the input are ignored for the purpose of computing\n" + "the lower and upper quantiles.\n" + "The quantile limits can be changed in WinsorizeOptions."), + {"array"}, "WinsorizeOptions", /*options_required=*/true); + +} // namespace + +void RegisterVectorStatistics(FunctionRegistry* registry) { + static const auto default_winsorize_options = WinsorizeOptions(); + + auto winsorize = std::make_shared<VectorFunction>( + "winsorize", Arity::Unary(), winsorize_doc, &default_winsorize_options); + + VectorKernel base; + base.init = WinsorizeState::Init; + base.mem_allocation = MemAllocation::NO_PREALLOCATE; + base.null_handling = NullHandling::COMPUTED_NO_PREALLOCATE; + base.can_execute_chunkwise = false; + // The variable is ill-named, but since we output a ChunkedArray ourselves, + // the function execution logic shouldn't try to wrap it again. + base.output_chunked = false; + + for (const auto& ty : NumericTypes()) { + base.signature = KernelSignature::Make({ty->id()}, &ResolveWinsorizeOutput); + base.exec = GenerateNumeric<Winsorize, /*Unused*/ void>(ty->id()); Review Comment: Well, it's not the parameter name, the comment just flags that the `Winsorize` class will ignore that parameter. -- This is an automated message from the Apache Git Service. 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