zanmato1984 commented on code in PR #44394: URL: https://github.com/apache/arrow/pull/44394#discussion_r1916804555
########## cpp/src/arrow/compute/kernels/vector_swizzle.cc: ########## @@ -0,0 +1,422 @@ +// 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 "arrow/compute/api_vector.h" + +#include "arrow/compute/api_vector.h" +#include "arrow/compute/function.h" +#include "arrow/compute/kernels/codegen_internal.h" +#include "arrow/compute/registry.h" +#include "arrow/util/checked_cast.h" +#include "arrow/util/logging.h" + +namespace arrow::compute::internal { + +namespace { + +// ---------------------------------------------------------------------- +// InversePermutation + +const FunctionDoc inverse_permutation_doc( + "Return the inverse permutation of the given indices", + "For the `i`-th `index` in `indices`, the `index`-th output is `i`", {"indices"}); + +const InversePermutationOptions* GetDefaultInversePermutationOptions() { + static const auto kDefaultInversePermutationOptions = + InversePermutationOptions::Defaults(); + return &kDefaultInversePermutationOptions; +} + +using InversePermutationState = OptionsWrapper<InversePermutationOptions>; + +/// Resolve the output type of inverse_permutation. The output type is specified in the +/// options, and if null, set it to the input type. The output type must be signed +/// integer. +Result<TypeHolder> ResolveInversePermutationOutputType( + KernelContext* ctx, const std::vector<TypeHolder>& input_types) { + DCHECK_EQ(input_types.size(), 1); + DCHECK_NE(input_types[0], nullptr); + + std::shared_ptr<DataType> output_type = InversePermutationState::Get(ctx).output_type; + if (!output_type) { + output_type = input_types[0].owned_type; + } + if (!is_signed_integer(output_type->id())) { + return Status::TypeError( + "Output type of inverse_permutation must be signed integer, got " + + output_type->ToString()); + } + + return TypeHolder(std::move(output_type)); +} + +template <typename ExecType> +struct InversePermutationImpl { + using ThisType = InversePermutationImpl<ExecType>; + using IndexType = typename ExecType::IndexType; + using IndexCType = typename IndexType::c_type; + using ShapeType = typename ExecType::ShapeType; + + static Result<std::shared_ptr<ArrayData>> Exec( + KernelContext* ctx, const ShapeType& indices, int64_t input_length, + const std::shared_ptr<DataType>& input_type) { + const auto& options = InversePermutationState::Get(ctx); + + // Apply default options semantics. + int64_t output_length = options.max_index < 0 ? input_length : options.max_index + 1; + std::shared_ptr<DataType> output_type = options.output_type; + if (!output_type) { + output_type = input_type; + } + + ThisType impl(ctx, indices, input_length, output_length); + RETURN_NOT_OK(VisitTypeInline(*output_type, &impl)); + + return ArrayData::Make(std::move(output_type), output_length, + {std::move(impl.validity_buf_), std::move(impl.data_buf_)}); + } + + template <typename Type> + enable_if_t<is_integer_type<Type>::value, Status> Visit(const Type& output_type) { + using OutputCType = typename Type::c_type; + + RETURN_NOT_OK(CheckInput(output_type)); + + // Dispatch the execution based on whether there are likely many nulls in the output. + // - If many nulls (i.e. the output is "sparse"), preallocate an all-false validity + // buffer and a zero-initialized data buffer (just to avoid exposing previous memory + // contents - even if it is shadowed by the validity bit). The subsequent processing + // will fill the valid values only. + // - Otherwise (i.e. the output is "dense"), the validity buffer is lazily allocated + // and initialized all-true in the subsequent processing only when needed. The data + // buffer is preallocated and filled with "impossible" values (that is, input_length - + // note that the range of inverse_permutation is [0, input_length)) for the subsequent + // processing to detect validity. + if (LikelyManyNulls()) { + RETURN_NOT_OK(AllocateValidityBufAndFill(false)); + RETURN_NOT_OK(AllocateDataBufAndZero(output_type)); + return Execute<Type, true>(); + } else { + RETURN_NOT_OK( + AllocateDataBufAndFill(output_type, static_cast<OutputCType>(input_length_))); + return Execute<Type, false>(); + } + } + + Status Visit(const DataType& output_type) { + DCHECK(false) << "Shouldn't reach here"; + return Status::Invalid("Shouldn't reach here"); + } + + private: + KernelContext* ctx_; + const ShapeType& indices_; + const int64_t input_length_; + const int64_t output_length_; + + std::shared_ptr<Buffer> validity_buf_; + std::shared_ptr<Buffer> data_buf_; + + InversePermutationImpl(KernelContext* ctx, const ShapeType& indices, + int64_t input_length, int64_t output_length) + : ctx_(ctx), + indices_(indices), + input_length_(input_length), + output_length_(output_length) {} + + template <typename Type> + Status CheckInput(const Type& output_type) { + using OutputCType = typename Type::c_type; + + if (static_cast<int64_t>(std::numeric_limits<OutputCType>::max()) < input_length_) { + return Status::Invalid( + "Output type " + output_type.ToString() + + " of inverse_permutation is insufficient to store indices of length " + + std::to_string(input_length_)); + } + + return Status::OK(); + } + + bool LikelyManyNulls() { return output_length_ > 2 * input_length_; } + + Status AllocateValidityBufAndFill(bool valid) { + DCHECK_EQ(validity_buf_, nullptr); + + ARROW_ASSIGN_OR_RAISE(validity_buf_, + AllocateEmptyBitmap(output_length_, ctx_->memory_pool())); + auto validity = validity_buf_->mutable_data_as<uint8_t>(); + std::memset(validity, valid ? 0xff : 0, validity_buf_->size()); Review Comment: Very useful advice! 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