edponce commented on a change in pull request #11937: URL: https://github.com/apache/arrow/pull/11937#discussion_r772452442
########## File path: cpp/src/arrow/compute/kernels/vector_is_monotonic.cc ########## @@ -0,0 +1,317 @@ +// 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/kernel.h" +#include "arrow/compute/kernels/aggregate_internal.h" +#include "arrow/compute/registry.h" +#include "arrow/util/optional.h" + +namespace arrow { +namespace compute { +namespace internal { + +namespace { +// ---------------------------------------------------------------------- +// IsMonotonic implementation + +using IsMonotonicState = OptionsWrapper<IsMonotonicOptions>; + +Status IsMonotonicOutput(bool increasing, bool strictly_increasing, bool decreasing, + bool strictly_decreasing, Datum* out) { + ARROW_ASSIGN_OR_RAISE( + *out, StructScalar::Make({std::make_shared<BooleanScalar>(increasing), + std::make_shared<BooleanScalar>(strictly_increasing), + std::make_shared<BooleanScalar>(decreasing), + std::make_shared<BooleanScalar>(strictly_decreasing)}, + {"increasing", "strictly_increasing", "decreasing", + "strictly_decreasing"})); + return Status::OK(); +} + +template <typename DataType> +enable_if_floating_point<DataType> IsMonotonicCheck( + const typename DataType::c_type& current, const typename DataType::c_type& next, + bool* increasing, bool* strictly_increasing, bool* decreasing, + bool* strictly_decreasing, const IsMonotonicOptions& options) { + // Short circuit for NaNs. + // https://en.wikipedia.org/wiki/NaN#Comparison_with_NaN + if (std::isnan(current) || std::isnan(next)) { + *increasing = false; + *strictly_increasing = false; + *decreasing = false; + *strictly_decreasing = false; + } else { + bool equal = + // Approximately equal within some error bound (epsilon). + (options.floating_approximate && + (fabs(current - next) <= + static_cast<typename DataType::c_type>(options.epsilon))) || + // Or exactly equal. + current == next; + if (*increasing) { + if (!(equal || next > current)) { + *increasing = false; + *strictly_increasing = false; + } + } + if (*decreasing) { + if (!(equal || next < current)) { + *decreasing = false; + *strictly_decreasing = false; + } + } + if (*strictly_increasing) { + if (equal || !(next > current)) { + *strictly_increasing = false; + } + } + if (*strictly_decreasing) { + if (equal || !(next < current)) { + *strictly_decreasing = false; + } + } + } +} + +template <typename DataType> +enable_if_not_floating_point<DataType> IsMonotonicCheck( + const typename DataType::c_type& current, const typename DataType::c_type& next, Review comment: After reviewing this PR, I think implementations of `IsMonotonicCheck` can be categorized as follows based on `DataType`: * have `c_type` (e.g., primitive numeric, datetime, timestamp) * `c_type` is floating-point * `c_type` is not floating-point * do not have `c_type` (binary, string, intervals) * custom implementation for `binary` and `string` * custom implementation for intervals There would be at least 4 type-specific implementations of `IsMonotonicCheck`, where the the `enable_if` for this case would be of the form (pseudocode) [`enable_if_has_c_type and enable_if_not_floating_point`](https://github.com/apache/arrow/blob/master/cpp/src/arrow/type_traits.h#L748) -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
