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/*
* Copyright (C) 2024-2025 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <wtf/Vector.h>
namespace WTF {
namespace Xsum {
struct SmallAccumulator final {
explicit SmallAccumulator();
explicit SmallAccumulator(
Vector<int64_t> &&chunk, const int addsUntilPropagate, const int64_t inf,
const int64_t nan, const size_t sizeCount, const bool hasPosNumber
);
Vector<int64_t> chunk; // Chunks making up small accumulator
int addsUntilPropagate; // Number of remaining adds before carry
int64_t inf; // If non-zero, +Inf, -Inf, or NaN
int64_t nan; // If non-zero, a NaN value with payload
size_t sizeCount; // number of added values
bool hasPosNumber; // check if added values have at least one positive number
int carryPropagate();
COLD void addInfNan(int64_t ivalue);
inline void add1NoCarry(double value);
ALWAYS_INLINE void incrementWhenValueAdded(double value);
};
struct LargeAccumulator final {
Vector<uint64_t> chunk; // Chunks making up large accumulator
Vector<int_least16_t> count; // Counts of # adds remaining for chunks, or -1 if not used yet or special
Vector<uint64_t> chunksUsed; // Bits indicate chunks in use
uint64_t usedUsed; // Bits indicate chunk_used entries not 0
SmallAccumulator sacc; // The small accumulator to condense into
explicit LargeAccumulator();
void addLchunkToSmall(int_fast16_t ix);
COLD void largeAddValueInfNan(int_fast16_t ix, uint64_t uintv);
void transferToSmall();
};
class XsumInterface {
public:
virtual ~XsumInterface() = default;
virtual void addList(const std::span<const double> vec) = 0;
virtual void add(double value) = 0;
virtual double compute() = 0;
};
class XsumSmall final : public XsumInterface {
public:
explicit XsumSmall();
explicit XsumSmall(SmallAccumulator sacc);
void addList(const std::span<const double> vec) override;
void add(double value) override;
double compute() override;
private:
SmallAccumulator m_smallAccumulator;
};
class XsumLarge final : public XsumInterface {
public:
explicit XsumLarge();
void addList(const std::span<const double> vec) override;
void add(double value) override;
double compute() override;
private:
LargeAccumulator m_largeAccumulator;
};
} // namespace Xsum
// Threshold for PreciseSum to determine whether to use XsumSmall or XsumLarge
// If the expected array length is greater than PRECISE_SUM_THRESHOLD, use Xsum::XsumLarge;
// otherwise use Xsum::XsumSmall
constexpr uint64_t PRECISE_SUM_THRESHOLD = 1'000;
template<std::derived_from<Xsum::XsumInterface> T = Xsum::XsumSmall>
class PreciseSum final {
public:
explicit PreciseSum()
: m_xsum { T { } } { }
void addList(const std::span<const double> vec)
{
m_xsum.addList(vec);
}
void add(double value)
{
m_xsum.add(value);
}
double compute()
{
return m_xsum.compute();
}
private:
T m_xsum;
};
} // namespace WTF
using WTF::PreciseSum;
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