C++ 用1D Arrat中的项替换2D数组中的项的最快方法

我这里有一个关于入境替代的问题。假设我们有一个固定大小的矩阵（平方）（未排序的2D数组），一个数字替换策略列表和另一个数字替换策略列表。我们在矩阵上循环，如果条目与replacementPolicy中的（第一个）元素具有相同的值，我们记住位置i，并用substitudeNUMBER中的第i个元素替换该条目。听起来有点复杂，代码如下：

void substitute_entry() {
    // For each entry in the matrix
    for (int column = 0; column < MATRIX_SIZE; ++column) {
        for (int row = 0; row < MATRIX_SIZE; ++row) {
            // Search for the entry in the original number list
            // and replace it with corresponding the element in the substituted number list
            int index = -1;
            for (int i = 0; i < LIST_SIZE; i++) {
                if (replacementPolicy[i] == MATRIX[row][column]) {
                    index = i;
                }
            }

            MATRIX[row][column] = substitutedNUMBER[index];
        }
    }
}

#include <iostream>
#include <chrono>
#include <omp.h>

#define MATRIX_SIZE 1000
#define LIST_SIZE 1000

int arr[MATRIX_SIZE][MATRIX_SIZE];
int replacementPolicy[LIST_SIZE];
int substitutedNUMBER[MATRIX_SIZE];

void substitute_entry() {
    // For each entry in the matrix
    #pragma omp parallel for
    for (int column = 0; column < MATRIX_SIZE; ++column) {
        #pragma omp parallel for
        for (int row = 0; row < MATRIX_SIZE; ++row) {
            // Search for the entry in the original number list
            // and replace it with corresponding the element in the substituted number list
            int index = -1;
            for (int i = 0; i < LIST_SIZE; i++) {
                if (replacementPolicy[i] == arr[row][column]) {
                    index = i;
                }
            }

            arr[row][column] = substitutedNUMBER[index];
        }
    }
}

int main()
{
  omp_set_num_threads(4);
  for ( int i = 0; i<MATRIX_SIZE ; i++)
  {
    replacementPolicy[i] = i;
    substitutedNUMBER[i] = i;

    for ( int j=0; j<MATRIX_SIZE ; j++) 
    {
      arr[i][j] = i+j;
    }
  }

  auto start = std::chrono::high_resolution_clock::now();
  substitute_entry();
  auto end = std::chrono::high_resolution_clock::now();
  uint64_t diff = std::chrono::duration_cast<std::chrono::microseconds>(end-start).count();
  std::cerr << diff << '\n';
  return 0;
}

void substitute_entry（）{
//对于矩阵中的每个条目
for（int column=0；column

但是，我希望优化此代码以实现更快的运行时。我的第一个想法是切换for循环——首先切换列，然后切换行，但这不会显著影响运行时。我的第二个想法是使用更好的算法来替换条目，但不幸的是，我在测试时搞砸了。有没有更好的办法

---

谢谢大家!

我认为您的循环非常适合多线程解决方案，例如，使用OpenMP，凭借其功能，您可以预期性能会有显著提高。我对您的代码做了一些更改，如下所示：

void substitute_entry() {
    // For each entry in the matrix
    for (int column = 0; column < MATRIX_SIZE; ++column) {
        for (int row = 0; row < MATRIX_SIZE; ++row) {
            // Search for the entry in the original number list
            // and replace it with corresponding the element in the substituted number list
            int index = -1;
            for (int i = 0; i < LIST_SIZE; i++) {
                if (replacementPolicy[i] == MATRIX[row][column]) {
                    index = i;
                }
            }

            MATRIX[row][column] = substitutedNUMBER[index];
        }
    }
}

#include <iostream>
#include <chrono>
#include <omp.h>

#define MATRIX_SIZE 1000
#define LIST_SIZE 1000

int arr[MATRIX_SIZE][MATRIX_SIZE];
int replacementPolicy[LIST_SIZE];
int substitutedNUMBER[MATRIX_SIZE];

void substitute_entry() {
    // For each entry in the matrix
    #pragma omp parallel for
    for (int column = 0; column < MATRIX_SIZE; ++column) {
        #pragma omp parallel for
        for (int row = 0; row < MATRIX_SIZE; ++row) {
            // Search for the entry in the original number list
            // and replace it with corresponding the element in the substituted number list
            int index = -1;
            for (int i = 0; i < LIST_SIZE; i++) {
                if (replacementPolicy[i] == arr[row][column]) {
                    index = i;
                }
            }

            arr[row][column] = substitutedNUMBER[index];
        }
    }
}

int main()
{
  omp_set_num_threads(4);
  for ( int i = 0; i<MATRIX_SIZE ; i++)
  {
    replacementPolicy[i] = i;
    substitutedNUMBER[i] = i;

    for ( int j=0; j<MATRIX_SIZE ; j++) 
    {
      arr[i][j] = i+j;
    }
  }

  auto start = std::chrono::high_resolution_clock::now();
  substitute_entry();
  auto end = std::chrono::high_resolution_clock::now();
  uint64_t diff = std::chrono::duration_cast<std::chrono::microseconds>(end-start).count();
  std::cerr << diff << '\n';
  return 0;
}

#包括
#包括
#包括
#定义矩阵大小为1000
#定义列表大小为1000
int arr[矩阵大小][矩阵大小]；
int replacementPolicy[列表大小]；
整数替代数[矩阵大小]；
无效替代项（）{
//对于矩阵中的每个条目
#pragma-omp并行
for（int column=0；column