线程数组中的第一个线程在c中被跳过(有时)？
线程数组中的第一个线程在c中被跳过(有时)？
提问于 2019-03-01 03:10:32
我正在尝试用C语言编写一个多线程程序，它通过将数组分成多个分区来对它进行排序，然后每个线程都在自己的分区上工作。问题似乎是，有时线程1，有时线程2，在执行时会被跳过。我甚至还没有进行排序，只进行了比较。现在，我只想知道我的线程是否正常运行，但第一个线程似乎就是无法调度。我对C不是很在行，我真的在绞尽脑汁寻找可能出错的地方。
我知道每个线程都可以被调度程序暂停，但它们最终都应该完成，对吧？那么为什么我的前几个线程有时不能运行呢？
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <time.h>
#define SIZE 11
#define HM_SORTERS 4
void * sort(void * param);
void printArr(int * arr);
struct PartitionBounds {
int tid;
size_t start;
size_t end;
};
int array[SIZE] = {18, 12, 68, 59, 75, 73, 68, 4, 16, 94, 15};
int main() {
// srand(time(NULL));
// for (size_t i = 0; i < SIZE; i++) {
// array[i] = rand() % 100;
// }
printArr(array);
pthread_t sorters[HM_SORTERS];
for(int i=0;i<HM_SORTERS;i++) {
struct PartitionBounds bounds;
size_t coverage = SIZE / HM_SORTERS;
bounds.tid = i;
bounds.start = i * coverage;
bounds.end = i + 1 == HM_SORTERS ? SIZE - 1 : bounds.start + coverage - 1;
int status = pthread_create(&sorters[i], NULL, sort, &bounds);
if(status == 0) {
printf("\n--- Thread %d created successfully ---\n", i + 1);
printf("start: %zu, end: %zu\n", bounds.start, bounds.end);
} else {
printf("!!! Failed to create thread !!!\n");
return 0;
}
}
for(int i=0;i<HM_SORTERS;i++) {
pthread_join(sorters[i], NULL);
}
printf("\n\n----- Sorting completed -----\n\n");
return 0;
}
void * sort(void * param) {
struct PartitionBounds *bounds = param;
printf("\n\tin thread %d\n\n", bounds->tid + 1);
for(size_t i=bounds->start;i<=bounds->end;i++) {
for(size_t j=i+1;j<=bounds->end;j++) {
if(array[j] < array[i]) {
printf("Thread %d: %d is smaller than %d\n", bounds->tid + 1, array[j], array[i]);
}
}
}
pthread_exit(NULL);
}
void printArr(int * arr) {
int coverage = SIZE / HM_SORTERS;
for(int i=0;i<HM_SORTERS;i++) {
size_t partitionEnd = i + 1 == HM_SORTERS ? coverage + SIZE % HM_SORTERS : coverage;
for(int j=0;j<partitionEnd;j++) {
printf("%d", array[j + coverage * i]);
if(j+1 < partitionEnd) {
printf(", ");
}
}
if(i+1 < HM_SORTERS) {
printf(" | ");
}
}
printf("\n");
}输出：(典型，当线程被跳过时)
18, 12 | 68, 59 | 75, 73 | 68, 4, 16, 94, 15
--- Thread 1 created successfully ---
start: 0, end: 1
--- Thread 2 created successfully ---
start: 2, end: 3
in thread 1
--- Thread 3 created successfully ---
Thread 3: 73 is smaller than 75
in thread 3
Thread 3: 73 is smaller than 75
in thread 2
start: 4, end: 5
Thread 3: 73 is smaller than 75
Thread 4: 68 is smaller than 75
Thread 4: 4 is smaller than 75
Thread 4: 16 is smaller than 75
Thread 4: 15 is smaller than 75
--- Thread 4 created successfully ---
start: 6, end: 10
Thread 4: 68 is smaller than 73
Thread 4: 4 is smaller than 73
Thread 4: 16 is smaller than 73
Thread 4: 15 is smaller than 73
Thread 4: 4 is smaller than 68
Thread 4: 16 is smaller than 68
Thread 4: 15 is smaller than 68
Thread 4: 15 is smaller than 16
Thread 4: 15 is smaller than 94
in thread 4
Thread 4: 4 is smaller than 68
Thread 4: 16 is smaller than 68
Thread 4: 15 is smaller than 68
Thread 4: 15 is smaller than 16
Thread 4: 15 is smaller than 94
----- Sorting completed -----回答 1
Stack Overflow用户
发布于 2019-03-01 04:08:43
不使用malloc/free的替代解决方案。
struct PartitionBounds bounds[HM_SORTERS];
...
size_t coverage = SIZE / HM_SORTERS;
bounds[i].tid = i;
bounds[i].start = i * coverage;
bounds[i].end = i + 1 == HM_SORTERS ? SIZE - 1 : bounds[i].start + coverage - 1;
int status = pthread_create(&sorters[i], NULL, sort, &bounds[i]);
...页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/54932676
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