[英]Multithreading but first few threads are being skipped
已经几个小时了,我似乎无法理解这个问题。 构建此程序以从 1 到 10 计数。此程序的目标是使用多线程并根据它请求的线程数动态拆分数组。 问题是前 2 个线程被跳过,最后一个线程正在执行大部分过程。 我怀疑是 for 循环创建了线程。
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
typedef struct
{
int *array;
int batch;
int start;
int end;
} Parameter;
void *method(void *p)
{
Parameter *param = (Parameter *)p;
for (int i = param->start; i < param->end; i++)
{
printf("Start:%d\tEnd:%d\tIndex:%d\tValue:%d\n", param->start, param->end, i,param->array[i]);
}
}
int main(int argc, char **argv)
{
// Getting the user input
int array_length = atoi(argv[1]);
int batches = atoi(argv[2]);
printf("User specified Array:%d\tBatch:%d\n", array_length, batches);
// Creating an array
int *array = (int *)calloc(array_length, sizeof(int));
// Fill it up with some data
for (int i = 0; i < array_length; i++)
{
array[i] = i;
}
// Determine the Batches
int batch_size = array_length / batches;
int remainder = array_length % batches;
printf("%d\n", batch_size);
printf("%d\n", remainder);
int start = 0;
int end = 0;
int index =0;
// List of parameters
Parameter *param = (Parameter *)calloc(batches, sizeof(Parameter));
pthread_t *threads = (pthread_t *)calloc(batches, sizeof(pthread_t));
// Loop through each batch.
for (int i = 0; i < batches; i++)
{
printf("\n\nBatch number -> %d\n", i);
end = start + batch_size;
if (remainder > 0)
{
remainder --;
end ++;
}
// Fill the parameters
param[i].array = array;
param[i].end = end;
param[i].start = start;
param[i].batch = i;
// Call the thread.
pthread_create(threads + index, NULL, method, (void *)¶m[i]);
index++;
start = end;
}
for (int i = 0; i < batches; i++)
{
pthread_join(threads[i], NULL);
}
free(param);
free(threads);
free(array);
return 0;
}
一直在玩 for 循环的索引(第 57 行),因为我确定这是问题的原因。 得到了一些结果,但主要问题仍然存在。
代码按预期工作。 我是一个没有把 printf 放在空白 function 中的笨蛋。像这样:
void *method(void *p) {
Parameter *param = (Parameter *)p;
printf("\n\nBatch number -> %d\n", param->batch); //<-- moved from main method
for (int i = param->start; i < param->end; i++)
{
printf("Start:%d\tEnd:%d\tIndex:%d\tValue:%d\n", param->start, param->end, i,param->array[i]);
} }
感谢您指出该程序有效
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