86 lines
2.5 KiB
C++
86 lines
2.5 KiB
C++
// SPDX-FileCopyrightText: 2025 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
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// SPDX-License-Identifier: GPL-3.0-only
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#ifndef JFJOCH_TOPPIXELS_H
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#define JFJOCH_TOPPIXELS_H
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#include <array>
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#include <algorithm>
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#include <cstdint>
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#include <stdexcept>
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#include <vector>
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class TopPixels {
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public:
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struct Entry {
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int32_t value = 0;
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int32_t index = 0;
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};
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explicit TopPixels(int capacity = 20)
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: capacity_(std::clamp(capacity, 1, kMaxCapacity)) {}
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void Clear() noexcept { size_ = 0; }
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void Add(int32_t value, int32_t index) noexcept {
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const Entry e{value, index};
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if (size_ < capacity_) {
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InsertSorted_(e);
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return;
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}
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// Quick reject: if not better than the current smallest in top-K
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if (value <= top_[capacity_ - 1].value)
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return;
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ReplaceSmallestAndFixOrder_(e);
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}
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[[nodiscard]] int Capacity() const noexcept { return capacity_; }
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[[nodiscard]] int Size() const noexcept { return size_; }
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[[nodiscard]] bool Empty() const noexcept { return size_ == 0; }
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// Sorted descending by value; valid for i in [0, Size()).
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[[nodiscard]] const Entry& At(int i) const {
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if (i < 0 || i >= size_)
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throw std::out_of_range("TopPixels::At index out of range");
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return top_[i];
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}
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[[nodiscard]] const Entry& operator[](int i) const { return At(i); }
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// Convenience: copy results to a std::vector (still sorted descending).
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[[nodiscard]] std::vector<Entry> ToVector() const {
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return std::vector<Entry>(top_.begin(), top_.begin() + size_);
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}
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private:
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static constexpr int kMaxCapacity = 64; // hard cap for stack-friendly storage
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std::array<Entry, kMaxCapacity> top_{};
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int size_ = 0;
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int capacity_ = 20;
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void InsertSorted_(Entry e) noexcept {
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top_[size_] = e;
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++size_;
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// Bubble up to keep descending order by value
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for (int i = size_ - 1; i > 0 && top_[i].value > top_[i - 1].value; --i)
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std::swap(top_[i], top_[i - 1]);
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}
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void ReplaceSmallestAndFixOrder_(Entry e) noexcept {
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// Replace the smallest (last, because sorted descending)
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top_[capacity_ - 1] = e;
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// Bubble up to restore descending order
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for (int i = capacity_ - 1; i > 0 && top_[i].value > top_[i - 1].value; --i)
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std::swap(top_[i], top_[i - 1]);
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size_ = capacity_;
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}
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};
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#endif //JFJOCH_TOPPIXELS_H
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