此代码是为赋值给出的。但是,蝙蝠在计算pi蒙特卡洛函数中存在错误。从int到unsigned int的转换错误统计无效。林不知道这是否是有意的,但我一直无法纠正这个问题。如果你想知道这个函数是线程示例的一部分。任何建议是非常感谢将int无效转换为无符号整型
void *compute_pi(void *s)
{
int seed;
int ii;
int *hit_pointer;
int local_hits;
double rand_no_x;
double rand_no_y;
hit_pointer = (int *) s;
seed = *hit_pointer;
local_hits = 0;
for(ii=0; ii < sample_points_per_thread; ii++)
{
rand_no_x = (double) (rand_r(&seed))/(double)RAND_MAX;//*error is these lines
rand_no_y = (double) (rand_r(&seed))/(double)RAND_MAX;//*error is these lines
if(((rand_no_x - 0.5) * (rand_no_x - 0.5) +
(rand_no_y - 0.5) * (rand_no_y - 0.5)) < 0.25)//*error
local_hits++;
seed *= ii;
}
*hit_pointer = local_hits;
pthread_exit(0);
}
我做了一些调试,现在看看错误可能位于哪里。现在生病发布计算pi被调用的主要函数。我相信这是参数被分析为采样点和线程数量的地方。当我运行该程序后,它会要求输入,它会失败并出现segementation故障。有什么建议么?
#include <pthread.h>
#include <stdlib.h>
#include <stdio.h>
#define MAX_THREADS 512
void *compute_pi(void *);
int sample_points;
int total_hits;
int total_misses;
int hits[ MAX_THREADS ];
int sample_points_per_thread;
int num_threads;
int main(int argc, char *argv[])
{
/* local variables */
int ii;
int retval;
pthread_t p_threads[MAX_THREADS];
pthread_attr_t attr;
double computed_pi;
/* initialize local variables */
retval = 0;
pthread_attr_init(&attr);
pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM);
printf("Enter number of sample points: ");
scanf("%d", &sample_points);
printf("Enter number of threads: ");
scanf("%d%", &num_threads);
/* parse command line arguments into sample points and number of threads */
/* there is no error checking here!!!!! */
sample_points = atoi(argv[1]);
num_threads = atoi(argv[2]);
total_hits = 0;
sample_points_per_thread = sample_points/num_threads;
for(ii=0; ii<num_threads; ii++)
{
hits[ii] = ii;
pthread_create(&p_threads[ ii ], &attr, compute_pi, (void *) &hits[ii]);
}
for(ii=0; ii<num_threads; ii++)
{
pthread_join(p_threads[ ii ], NULL);
total_hits += hits[ ii ];
}
computed_pi = 4.0 * (double) total_hits/((double) (sample_points));
printf("Computed PI = %lf\n", computed_pi);
/* return to calling environment */
return(retval);
}
预期与否,原始的“修复”似乎源于声明'seed'匹配所提供的'void *'参数'hit_pointer'的强制类型。这个“比赛”结束。你是正确的,['rand_r()'](http://linux.die.net/man/3/rand_r)确实规定使用'unsigned int *'作为其单个参数。 – WhozCraig 2013-03-23 03:06:36
仔细阅读错误消息,不要将其解释。错误是**不是无效**将'int'转换为'unsigned';没关系。该错误是无效的'int *'转换为'unsigned *',这是非常不同的。 – 2013-03-23 11:13:16