使用MPI C ++进行代码合并排序时出错 [英] Error in code merge sort with MPI C++

问题描述

我有一个代码 - 在c ++中合并排序数组，但它不起作用。

我的代码：

I have a code - merge sort array in c++, but it doesn't work.
My code:

#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <cstdlib>
#include <time.h>
#include <mpi.h>


void merge(int *, int *, int, int, int);
void mergeSort(int *, int *, int, int);
void* malloc(size_t);

int main(int argc, char** argv) {

	/********** Create and populate the array **********/
	int n = atoi(argv[1]);
	int *original_array = malloc(n * sizeof(int));

	int c;
	srand(time(NULL));
	printf("This is the unsorted array: ");
	for (c = 0; c < n; c++) {

		original_array[c] = rand() % n;
		printf("%d ", original_array[c]);

	}

	printf("\n");
	printf("\n");

	/********** Initialize MPI **********/
	int world_rank;
	int world_size;

	MPI_Init(&argc, &argv);
	MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);
	MPI_Comm_size(MPI_COMM_WORLD, &world_size);

	/********** Divide the array in equal-sized chunks **********/
	int size = n / world_size;

	/********** Send each subarray to each process **********/
	int *sub_array = malloc(size * sizeof(int));
	MPI_Scatter(original_array, size, MPI_INT, sub_array, size, MPI_INT, 0, MPI_COMM_WORLD);

	/********** Perform the mergesort on each process **********/
	int *tmp_array = malloc(size * sizeof(int));
	mergeSort(sub_array, tmp_array, 0, (size - 1));

	/********** Gather the sorted subarrays into one **********/
	int *sorted = NULL;
	if (world_rank == 0) {

		sorted == malloc(n * sizeof(int));

	}

	MPI_Gather(sub_array, size, MPI_INT, sorted, size, MPI_INT, 0, MPI_COMM_WORLD);

	/********** Make the final mergeSort call **********/
	if (world_rank == 0) {

		int *other_array = malloc(n * sizeof(int));
		mergeSort(sorted, other_array, 0, (n - 1));

		/********** Display the sorted array **********/
		printf("This is the sorted array: ");
		for (c = 0; c < n; c++) {

			printf("%d ", sorted[c]);

		}

		printf("\n");
		printf("\n");

		/********** Clean up root **********/
		free(sorted);
		free(other_array);

	}

	/********** Clean up rest **********/
	free(original_array);
	free(sub_array);
	free(tmp_array);

	/********** Finalize MPI **********/
	MPI_Barrier(MPI_COMM_WORLD);
	MPI_Finalize();

}

/********** Merge Function **********/
void merge(int *a, int *b, int l, int m, int r) {

	int h, i, j, k;
	h = l;
	i = l;
	j = m + 1;

	while ((h <= m) && (j <= r)) {

		if (a[h] <= a[j]) {

			b[i] = a[h];
			h++;

		}

		else {

			b[i] = a[j];
			j++;

		}

		i++;

	}

	if (m < h) {

		for (k = j; k <= r; k++) {

			b[i] = a[k];
			i++;

		}

	}

	else {

		for (k = h; k <= m; k++) {

			b[i] = a[k];
			i++;

		}

	}

	for (k = l; k <= r; k++) {

		a[k] = b[k];

	}

}

/********** Recursive Merge Function **********/
void mergeSort(int *a, int *b, int l, int r) {

	int m;

	if (l < r) {

		m = (l + r) / 2;

		mergeSort(a, b, l, m);
		mergeSort(a, b, (m + 1), r);
		merge(a, b, l, m, r);

	}

}

错误：

Error:

Severity    Code    Description Project File    Line    Suppression State
Error (active)      a value of type "void *" cannot be used to initialize an entity of type "int *" ConsoleApplication2 c:\Users\Андрей\Desktop\ЛАБАТРИ\ConsoleApp2\ConsoleApplication2\ConsoleApplication2\ConsoleApplication2.cpp 16

在这一行：

At this line:

int *original_array = malloc(n * sizeof(int));

请帮助！



什么我试过了：



我试图用另一种方式编写数组，但它不起作用。我试着编写像

Help please!

What I have tried:

I tried to write array another way but it doesn't work. I tried to write like

void* malloc(size_t);

但它不起作用。

推荐答案

使用C ++，你必须强制转换 void * 返回值因为C ++使用强类型系统：

With C++, you must cast the void* return value because C++ uses a strong type system:

int *original_array = reinterpret_cast<int*>(malloc(n * sizeof(int)));

但是，对于C ++，你应该使用 new 和 delete 代替：

However, with C++ you should use new and delete instead:

int *original_array = new int[n];

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