Question

我有一个问题，但答案我没有找到。我写了一些组合学解算器和单独的主要保存结构，分成称为Matrix的类。我填写了回溯算法。当我创建一个指向Matrix的新指针实例并经常调用方法集并在类上取消设置时Matrix性能下降2倍。它比以前慢了2倍。但是，如果我创建嵌套类，性能将是正常的。但我不知道为什么？是否有任何解决方案如何没有嵌套类的单独类，但性能会好吗？感谢您的时间。我粘贴Matrix.h和Matrix.cpp。项目我在macOsx和linux上进行了测试，由g ++ 4.2.1和-O2声明编译

        class Matrix {
        private:
            int rows;
            int columns;
            int filledCells = { 0 };
            int * data = nullptr;
            int * freeCellInColumn = nullptr;
        public:
            Matrix(int rows, int columns);
            ~Matrix();
            void set(const int & column, const int & value);
            void unset(const int & column);
            int & get(const int & row, const int & column);
            int & getFreeCellsInColumn(const int & column);
            int getFilledCellsInColumn(const int & column);
            int * getData();
            const int & getFilledCells() const;
    };

和定义是

#include <stdexcept>
#include "Matrix.h"

Matrix::Matrix(int rows, int columns) {
    if (rows < 1 || columns < 1) {
        std::runtime_error("Number of rows or columns at matrix is invalid.\n");
    }
    this->rows = rows;
    this->columns = columns;
    this->data = new int [rows * columns]();
    this->freeCellInColumn = new int[columns]();
    for (int i = 0; i < columns; i++) {
        this->freeCellInColumn[i] = this->rows;
    }
}

Matrix::~Matrix() {
    delete [] this->data;
    this->data = nullptr;

    delete [] this->freeCellInColumn;
    freeCellInColumn = nullptr;
}

void Matrix::set(const int & column, const int & value) {
    this->data[(--this->freeCellInColumn[column]) * this->columns + column] =    value;
    ++this->filledCells;
}

void Matrix::unset(const int & column) {
    this->data[(this->freeCellInColumn[column]++) * this->columns + column] = 0;
    --this->filledCells;
}

int * Matrix::getData() {
    return this->data;
}

int & Matrix::get(const int & row, const int & column) {
    return this->data[row * this->columns + column];
}

const int & Matrix::getFilledCells() const {
    return this->filledCells;
}

int & Matrix::getFreeCellsInColumn(const int & column) {
    return this->freeCellInColumn[column];
}

int Matrix::getFilledCellsInColumn(const int & column) {
    return this->rows - this->freeCellInColumn[column];
}

我粘贴嵌套类的部分，我在Labeling类中的嵌套类的意思是在类标签中声明类Matrix， method int * getData（）我只使用一次打印结果。

class Labelling {
private:
    class Matrix {
        private:
            int rows;
            int columns;
            int filledCells = { 0 };
            int * data = nullptr;
            int * freeCellInColumn = nullptr;
        public:
            Matrix(int rows, int columns);
            ~Matrix();
            void set(const int & column, const int & value);
            void unset(const int & column);
            int & get(const int & row, const int & column);
            int & getFreeCellsInColumn(const int & column);
            int getFilledCellsInColumn(const int & column);
            int * getData();
            const int & getFilledCells() const;
    };
    TextPrinter * printer;
    NSumProblemSolver * solver;
    Matrix * solution;
    ...};

C ++ 11嵌套类比单独的类更快

0 个答案: