问题描述
为什么当我要编译以下多线程合并排序C程序时,收到此错误:
Why when I wan to compile the following multi thread merge sorting C program, I receive this error:
ap@sharifvm:~/forTHE04a$ gcc -g -Wall -o mer mer.c -lpthread
mer.c:4:20: fatal error: iostream: No such file or directory
#include <iostream>
^
compilation terminated.
ap@sharifvm:~/forTHE04a$ gcc -g -Wall -o mer mer.c -lpthread
mer.c:4:22: fatal error: iostream.h: No such file or directory
#include <iostream.h>
^
compilation terminated.
我的程序:
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <iostream>
using namespace std;
#define N 2 /* # of thread */
int a[] = {10, 9, 8, 7, 6, 5, 4, 3, 2, 1}; /* target array */
/* structure for array index
* used to keep low/high end of sub arrays
*/
typedef struct Arr {
int low;
int high;
} ArrayIndex;
void merge(int low, int high)
{
int mid = (low+high)/2;
int left = low;
int right = mid+1;
int b[high-low+1];
int i, cur = 0;
while(left <= mid && right <= high) {
if (a[left] > a[right])
b[cur++] = a[right++];
else
b[cur++] = a[right++];
}
while(left <= mid) b[cur++] = a[left++];
while(right <= high) b[cur++] = a[left++];
for (i = 0; i < (high-low+1) ; i++) a[low+i] = b[i];
}
void * mergesort(void *a)
{
ArrayIndex *pa = (ArrayIndex *)a;
int mid = (pa->low + pa->high)/2;
ArrayIndex aIndex[N];
pthread_t thread[N];
aIndex[0].low = pa->low;
aIndex[0].high = mid;
aIndex[1].low = mid+1;
aIndex[1].high = pa->high;
if (pa->low >= pa->high) return 0;
int i;
for(i = 0; i < N; i++) pthread_create(&thread[i], NULL, mergesort, &aIndex[i]);
for(i = 0; i < N; i++) pthread_join(thread[i], NULL);
merge(pa->low, pa->high);
//pthread_exit(NULL);
return 0;
}
int main()
{
ArrayIndex ai;
ai.low = 0;
ai.high = sizeof(a)/sizeof(a[0])-1;
pthread_t thread;
pthread_create(&thread, NULL, mergesort, &ai);
pthread_join(thread, NULL);
int i;
for (i = 0; i < 10; i++) printf ("%d ", a[i]);
cout << endl;
return 0;
}
推荐答案
都不是< iostream>
或< iostream.h>
是标准的C头文件。您的代码应为C ++,其中< iostream>
是有效的标头。对于C ++代码,使用 g ++
(以及 .cpp
文件扩展名)。
Neither <iostream>
nor <iostream.h>
are standard C header files. Your code is meant to be C++, where <iostream>
is a valid header. Use g++
(and a .cpp
file extension) for C++ code.
或者,此程序主要使用无论如何都可以在C中使用的构造。将整个程序转换为使用C编译器进行编译非常容易。只需使用命名空间std删除 #include< iostream>
和,并替换
cout< ;< endl;
与 putchar('\n');
...我建议使用C99进行编译(例如 gcc -std = c99
)
Alternatively, this program uses mostly constructs that are available in C anyway. It's easy enough to convert the entire program to compile using a C compiler. Simply remove #include <iostream>
and using namespace std;
, and replace cout << endl;
with putchar('\n');
... I advise compiling using C99 (eg. gcc -std=c99
)
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