cpp-ch/local-engine/Functions/SparkFunctionRoundHalfUp.h

/*
 * 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.
 */
#pragma once

#include <Functions/FunctionsRound.h>


namespace local_engine
{
using namespace DB;

template <typename T>
class BaseFloatRoundingHalfUpComputation
{
public:
    using ScalarType = T;
    using VectorType = Float64;
    static const size_t data_count = 1;

    static VectorType load(const ScalarType * in) { return static_cast<VectorType>(*in); }
    static VectorType load1(ScalarType in) { return in; }
    static ScalarType store(ScalarType * out, VectorType val) { return *out = static_cast<ScalarType>(val); }
    static VectorType multiply(VectorType val, VectorType scale) { return val * scale; }
    static VectorType divide(VectorType val, VectorType scale) { return val / scale; }
    static VectorType apply(VectorType val) { return round(val); }
    static VectorType prepare(size_t scale) { return load1(scale); }
};


/** Implementation of low-level round-off functions for floating-point values.
  */
template <typename T, ScaleMode scale_mode>
class FloatRoundingHalfUpComputation : public BaseFloatRoundingHalfUpComputation<T>
{
    using Base = BaseFloatRoundingHalfUpComputation<T>;

public:
    static inline void compute(const T * __restrict in, const typename Base::VectorType & scale, T * __restrict out)
    {
        auto val = Base::load(in);

        if (scale_mode == ScaleMode::Positive)
            val = Base::multiply(val, scale);
        else if (scale_mode == ScaleMode::Negative)
            val = Base::divide(val, scale);

        val = Base::apply(val);

        if (scale_mode == ScaleMode::Positive)
            val = Base::divide(val, scale);
        else if (scale_mode == ScaleMode::Negative)
            val = Base::multiply(val, scale);

        Base::store(out, val);
    }
};


/** Implementing high-level rounding functions.
  */
template <typename T, ScaleMode scale_mode>
struct FloatRoundingHalfUpImpl
{
private:
    static_assert(!is_decimal<T>);

    using Op = FloatRoundingHalfUpComputation<T, scale_mode>;
    using Data = std::array<T, Op::data_count>;
    using ColumnType = ColumnVector<T>;
    using Container = typename ColumnType::Container;

public:
    static NO_INLINE void apply(const Container & in, size_t scale, Container & out)
    {
        auto mm_scale = Op::prepare(scale);

        const size_t data_count = std::tuple_size<Data>();

        const T* end_in = in.data() + in.size();
        const T* limit = in.data() + in.size() / data_count * data_count;

        const T* __restrict p_in = in.data();
        T* __restrict p_out = out.data();

        while (p_in < limit)
        {
            Op::compute(p_in, mm_scale, p_out);
            p_in += data_count;
            p_out += data_count;
        }

        if (p_in < end_in)
        {
            Data tmp_src{{}};
            Data tmp_dst;

            size_t tail_size_bytes = (end_in - p_in) * sizeof(*p_in);

            memcpy(&tmp_src, p_in, tail_size_bytes);
            Op::compute(reinterpret_cast<T *>(&tmp_src), mm_scale, reinterpret_cast<T *>(&tmp_dst));
            memcpy(p_out, &tmp_dst, tail_size_bytes);
        }
    }
};


/** Select the appropriate processing algorithm depending on the scale.
  */
template <typename T, RoundingMode rounding_mode, TieBreakingMode tie_breaking_mode>
struct DispatcherRoundingHalfUp
{
    template <ScaleMode scale_mode>
    using FunctionRoundingImpl = std::conditional_t<std::is_floating_point_v<T>,
                                                    FloatRoundingHalfUpImpl<T, scale_mode>,
                                                    IntegerRoundingImpl<T, rounding_mode, scale_mode, tie_breaking_mode>>;

    static ColumnPtr apply(const IColumn * col_general, Scale scale_arg)
    {
        const auto * const col = checkAndGetColumn<ColumnVector<T>>(col_general);
        auto col_res = ColumnVector<T>::create();

        typename ColumnVector<T>::Container & vec_res = col_res->getData();
        vec_res.resize(col->getData().size());

        if (!vec_res.empty())
        {
            if (scale_arg == 0)
            {
                size_t scale = 1;
                FunctionRoundingImpl<ScaleMode::Zero>::apply(col->getData(), scale, vec_res);
            }
            else if (scale_arg > 0)
            {
                size_t scale = intExp10(scale_arg);
                FunctionRoundingImpl<ScaleMode::Positive>::apply(col->getData(), scale, vec_res);
            }
            else
            {
                size_t scale = intExp10(-scale_arg);
                FunctionRoundingImpl<ScaleMode::Negative>::apply(col->getData(), scale, vec_res);
            }
        }

        return col_res;
    }
};

template <is_decimal T, RoundingMode rounding_mode, TieBreakingMode tie_breaking_mode>
struct DispatcherRoundingHalfUp<T, rounding_mode, tie_breaking_mode>
{
public:
    static ColumnPtr apply(const IColumn * col_general, Scale scale_arg)
    {
        const auto * const col = checkAndGetColumn<ColumnDecimal<T>>(col_general);
        const typename ColumnDecimal<T>::Container & vec_src = col->getData();

        auto col_res = ColumnDecimal<T>::create(vec_src.size(), col->getScale());
        auto & vec_res = col_res->getData();

        if (!vec_res.empty())
            DecimalRoundingImpl<T, rounding_mode, tie_breaking_mode>::apply(col->getData(), col->getScale(), vec_res, scale_arg);

        return col_res;
    }
};

/** A template for functions that round the value of an input parameter of type
  * (U)Int8/16/32/64, Float32/64 or Decimal32/64/128, and accept an additional optional parameter (default is 0).
  */
template <typename Name, RoundingMode rounding_mode, TieBreakingMode tie_breaking_mode>
class FunctionRoundingHalfUp : public IFunction
{
public:
    static constexpr auto name = "roundHalfUp";
    static FunctionPtr create(ContextPtr) { return std::make_shared<FunctionRoundingHalfUp>(); }

    String getName() const override
    {
        return name;
    }

    bool isVariadic() const override { return true; }
    size_t getNumberOfArguments() const override { return 0; }
    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }

    /// Get result types by argument types. If the function does not apply to these arguments, throw an exception.
    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
    {
        if ((arguments.empty()) || (arguments.size() > 2))
            throw Exception(ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH,
                            "Number of arguments for function {} doesn't match: passed {}, should be 1 or 2.",
                            getName(), arguments.size());

        for (const auto & type : arguments)
            if (!isNumber(type))
                throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Illegal type {} of argument of function {}",
                                arguments[0]->getName(), getName());

        return arguments[0];
    }

    static Scale getScaleArg(const ColumnsWithTypeAndName & arguments)
    {
        if (arguments.size() == 2)
        {
            const IColumn & scale_column = *arguments[1].column;
            if (!isColumnConst(scale_column))
                throw Exception(ErrorCodes::ILLEGAL_COLUMN, "Scale argument for rounding functions must be constant");

            Field scale_field = assert_cast<const ColumnConst &>(scale_column).getField();
            if (scale_field.getType() != Field::Types::UInt64
                && scale_field.getType() != Field::Types::Int64)
                throw Exception(ErrorCodes::ILLEGAL_COLUMN, "Scale argument for rounding functions must have integer type");

            Int64 scale64 = scale_field.get<Int64>();
            if (scale64 > std::numeric_limits<Scale>::max()
                || scale64 < std::numeric_limits<Scale>::min())
                throw Exception(ErrorCodes::ARGUMENT_OUT_OF_BOUND, "Scale argument for rounding function is too large");

            return scale64;
        }
        return 0;
    }

    bool useDefaultImplementationForConstants() const override { return true; }
    ColumnNumbers getArgumentsThatAreAlwaysConstant() const override { return {1}; }

    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t /*input_rows_count*/) const override
    {
        const ColumnWithTypeAndName & column = arguments[0];
        Scale scale_arg = getScaleArg(arguments);

        ColumnPtr res;
        auto call = [&](const auto & types) -> bool
        {
            using Types = std::decay_t<decltype(types)>;
            using DataType = typename Types::LeftType;

            if constexpr (IsDataTypeNumber<DataType> || IsDataTypeDecimal<DataType>)
            {
                using FieldType = typename DataType::FieldType;
                res = DispatcherRoundingHalfUp<FieldType, rounding_mode, tie_breaking_mode>::apply(column.column.get(), scale_arg);
                return true;
            }
            return false;
        };

        if (!callOnIndexAndDataType<void>(column.type->getTypeId(), call))
        {
            throw Exception(ErrorCodes::ILLEGAL_COLUMN, "Illegal column {} of argument of function {}", column.name, getName());
        }

        return res;
    }

    bool hasInformationAboutMonotonicity() const override
    {
        return true;
    }

    Monotonicity getMonotonicityForRange(const IDataType &, const Field &, const Field &) const override
    {
        return { .is_monotonic = true, .is_always_monotonic = true };
    }
};


struct NameRoundHalfUp { static constexpr auto name = "roundHalfUp"; };

using FunctionRoundHalfUp = FunctionRoundingHalfUp<NameRoundHalfUp, RoundingMode::Round, TieBreakingMode::Auto>;

}