因此，我仔细研究了所有我可以在堆栈上和许多其他来源上解决的问题。虽然我能够解决一些问题并添加一些额外的测试，但仍无法解决我的问题。该程序是通过mergesort.c设置的，mergesort.c调用函数mergesortTest.c来测试我的函数。串行实现工作正常。我克服了最初创建的问题。但是，现在我试图加入他们，我遇到了段错误。香港专业教育学院使用valgrind和gdb来测试它，并在我的联接。虽然我无法打印出错误消息，因为它会导致段错误并关闭程序。香港专业教育学院确保尝试分配适当的空间。但是请把我的代码和gdb的输出发布给我们，希望有人能帮助我解决这个问题。
**mergesort.c**
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#define TRUE 1
#define FALSE 0
#define MAX 100000000
#define MAX_CORE 4
// function prototypes
void serial_mergesort(int A[], int p, int r);
void merge(int A[], int p, int q, int r);
void insertion_sort(int A[], int p, int r);
void *pthread_mergesort(void *arg);
struct mergeS
{
int numElements;
int *A;
int level;
int Max_Level;
};
const int INSERTION_SORT_THRESHOLD = 100; //based on trial and error
/*
* insertion_sort(int A[], int p, int r):
*
* description: Sort the section of the array A[p..r].
*/
void insertion_sort(int A[], int p, int r)
{
int j;
for (j=p+1; j<=r; j++) {
int key = A[j];
int i = j-1;
while ((i > p-1) && (A[i] > key)) {
A[i+1] = A[i];
i--;
}
A[i+1] = key;
}
}
/*
* serial_mergesort(int A[], int p, int r):
*
* description: Sort the section of the array A[p..r].
*/
void serial_mergesort(int A[], int p, int r)
{
if (r-p+1 <= INSERTION_SORT_THRESHOLD) {
insertion_sort(A,p,r);
} else {
int q = (p+r)/2;
serial_mergesort(A, p, q);
serial_mergesort(A, q+1, r);
merge(A, p, q, r);
}
}
/*
* pthread_mergesort(void *arg)
*
* description:Sorts based off levels
*
*/
void *pthread_mergesort(void *arg)
{
struct mergeS *threader = (struct mergeS*) arg;
int i = 0;
int flag = 0;
int level = (threader)->level;
printf("level: %d\n",level);
int numElements = threader->numElements;
int Max_Level = threader->Max_Level;
int *A = threader->A;
if(Max_Level == 1)
{
serial_mergesort(A,1,numElements + 1);
return NULL;
}
int low = level * (numElements/Max_Level) + 1;
int high =((level + 1) * ((numElements/Max_Level)));
pthread_t *tids = (pthread_t*) malloc(sizeof(pthread_t) * 2);
struct mergeS *merger = (struct mergeS*) malloc(sizeof(struct mergeS) * 2);
int error = 0;
if(level < Max_Level - 1)
{
for(i = 0;i < 2; i ++)
{
printf("for loop\n");
merger[i].numElements = numElements/(i + 1);
merger[i].level = threader->level + 1;
merger[i].Max_Level = threader->Max_Level;
merger[i].A = threader->A;
if((error = pthread_create(&tids[i],NULL,pthread_mergesort,(void*)&merger[i])) == 0)
{
printf("thread failed\n");
flag = 1;
}
}
printf("error: %d\n",error);
}
serial_mergesort(A,low,high);
int j = 0;
if(flag == 0)
{
for(j = 0;j < 2; j++)
{
printf("for level: %d\n",threader->level);
printf("join = %d\n", j);
if((error = pthread_join(tids[j],NULL)) != 0)
{
printf("error: %d\n",error);
}
}
}
merge(A,low,(high/2) + 1,high);
free(merger);
free (tids);
return NULL;
}
/*
* merge(int A[], int p, int q, int r):
*
* description: Merge two sorted sequences A[p..q] and A[q+1..r]
* and place merged output back in array A. Uses extra
* space proportional to A[p..r].
*/
void merge(int A[], int p, int q, int r)
{
int *B = (int *) malloc(sizeof(int) * (r-p+1));
int i = p;
int j = q+1;
int k = 0;
int l;
// as long as both lists have unexamined elements
// this loop keeps executing.
while ((i <= q) && (j <= r)) {
if (A[i] < A[j]) {
B[k] = A[i];
i++;
} else {
B[k] = A[j];
j++;
}
k++;
}
// now only at most one list has unprocessed elements.
if (i <= q) {
// copy remaining elements from the first list
for (l=i; l<=q; l++) {
B[k] = A[l];
k++;
}
} else {
// copy remaining elements from the second list
for (l=j; l<=r; l++) {
B[k] = A[l];
k++;
}
}
// copy merged output from array B back to array A
k=0;
for (l=p; l<=r; l++) {
A[l] = B[k];
k++;
}
free(B);
}
文件尾
**mergesortTest.c**
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#define MAX_THREAD 4
#define TRUE 1
#define FALSE 0
// function prototypes
int check_if_sorted(int A[], int n);
void generate_random_array(int A[], int n, int seed);
void serial_mergesort(int A[], int p, int r);
void *pthread_mergesort(void *arg);
void merge(int A[], int p, int q, int r);
void insertion_sort(int A[], int p, int r);
double getMilliSeconds();
// Struct
struct mergeS
{
int numElements;
int *A;
int level;
int Max_Level;
};
/*
* generate_random_array(int A[], int n, int seed):
*
* description: Generate random integers in the range [0,RANGE]
* and store in A[1..n]
*/
#define RANGE 1000000
void generate_random_array(int A[], int n, int seed)
{
int i;
srandom(seed);
for (i=1; i<=n; i++){
A[i] = random()%RANGE;
}
}
/*
* check_if_sorted(int A[], int n):
*
* description: returns TRUE if A[1..n] are sorted in nondecreasing order
* otherwise returns FALSE
*/
int check_if_sorted(int A[], int n)
{
int i=0;
for (i=1; i<n; i++) {
if (A[i] > A[i+1]) {
printf("%d > %d\n",A[i],A[i+1]);
printf("i: %d\n",i);
return FALSE;
}
}
return TRUE;
}
int main(int argc, char **argv) {
printf("argc = %d\n",argc);
int n;
int Max_Level = 4;
int flag = 1;
int seed;
if (argc == 1) { // there must be at least one command-line argument
printf("Default: Input Size = 100000000 levels: 4\n");
printf("Usage: executable input size number of levels\n");
n = 100000000;
seed = 4;
flag = 0;
}
if (argc == 2 && flag == 1) {
printf("Default: Threads: 4\n");
printf("Usage: executable input size number of levels\n");
n = atoi(argv[1]);
Max_Level = 4;
seed = 4;
}
if(argc == 3)
{
n = atoi(argv[1]);
Max_Level = atoi(argv[2]);
seed = Max_Level;
}
if(Max_Level > 15)
{
printf("To many levels. Setting to 4\n");
Max_Level = 4;
seed = Max_Level;
}
int *A = (int *) malloc(sizeof(int) * (n+1)); // n+1 since we are using A[1]..A[n]
// generate random input
generate_random_array(A,n,seed);
double start_time;
double sorting_time;
// sort the input (and time it)
start_time = getMilliSeconds();
serial_mergesort(A,1,n);
sorting_time = getMilliSeconds() - start_time;
////////////////////////////////////////////////////////////////////////////////////////////////////// Start of parallel //////////////////////////////////////////////////////////////////////////////////////////////////////
int *B = (int *) malloc(sizeof(int) * (n+1)); // n+1 since we are using A[1]..A[n]
//int i;
double p_start_time;
double p_sorting_time;
struct mergeS *threader = (struct mergeS*) malloc(sizeof(struct mergeS));
generate_random_array(B,n,seed);
// sort the input with threads (and time it)
p_start_time = getMilliSeconds();
threader[0].numElements = n;
threader[0].level = 0;
threader[0].Max_Level = Max_Level;
threader[0].A = B;
pthread_mergesort(threader);
printf("sorted\n");
/*for(i = 0;i < n + 1;i = i + 1)
{
printf("B[%d]: %d\n",i,B[i]);
}
printf("B:[%d] = %d\n",999,B[999]);
*/
p_sorting_time = getMilliSeconds() - p_start_time;
// print results if correctly sorted otherwise cry foul and exit
if (check_if_sorted(A,n)) {
printf("Serial: Sorting %d elements took %4.2lf seconds.\n", n, sorting_time/1000.0);
} else {
printf("%s: sorting failed!!!!\n", argv[0]);
exit(EXIT_FAILURE);
}
if (check_if_sorted(B,n)) {
printf("Threaded: Sorting %d elements took %4.2lf seconds.\n", n, p_sorting_time/1000.0);
} else {
printf("%s: parallel sorting failed!!!!\n", argv[0]);
exit(EXIT_FAILURE);
}
free(threader);
free(A);
free(B);
exit(EXIT_SUCCESS);
}
文件结尾
**GBD error report and code output**
[rutgerluther@onyxnode72 multi-threaded]$ valgrind --leak-check=yes ./mergesort 1000 2
==5636== Memcheck, a memory error detector
==5636== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==5636== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==5636== Command: ./mergesort 1000 2
==5636==
argc = 3
level: 0
for loop
thread failed
for loop
thread failed
error: 0
sorted
Serial: Sorting 1000 elements took 0.00 seconds.
993090 > 163007
i: 500
./mergesort: parallel sorting failed!!!!
==5636==
==5636== HEAP SUMMARY:
==5636== in use at exit: 9,152 bytes in 5 blocks
==5636== total heap usage: 30 allocs, 25 frees, 33,216 bytes allocated
==5636==
==5636== 1,120 bytes in 2 blocks are possibly lost in loss record 2 of 4
==5636== at 0x4C2B9B5: calloc (vg_replace_malloc.c:711)
==5636== by 0x40128C4: _dl_allocate_tls (in /usr/lib64/ld-2.17.so)
==5636== by 0x4E3E7FB: pthread_create@@GLIBC_2.2.5 (in /usr/lib64/libpthread-2.17.so)
==5636== by 0x400E88: pthread_mergesort (mergesort.c:114)
==5636== by 0x400B00: main (mergesortTest.c:145)
==5636==
==5636== LEAK SUMMARY:
==5636== definitely lost: 0 bytes in 0 blocks
==5636== indirectly lost: 0 bytes in 0 blocks
==5636== possibly lost: 1,120 bytes in 2 blocks
==5636== still reachable: 8,032 bytes in 3 blocks
==5636== suppressed: 0 bytes in 0 blocks
==5636== Reachable blocks (those to which a pointer was found) are not shown.
==5636== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==5636==
==5636== For counts of detected and suppressed errors, rerun with: -v
==5636== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
[rutgerluther@onyxnode72 multi-threaded]$ gdb ./mergesort
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-110.el7
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/RutgerLuther/RutgerLuther@u.boisestate.edu/backpack/CS453-1-f18/p2/multi-threaded/mergesort...done.
(gdb) b 130
Breakpoint 1 at 0x400abd: file mergesortTest.c, line 130.
(gdb) r 1000 2
Starting program: /home/RutgerLuther/RutgerLuther@u.boisestate.edu/backpack/CS453-1-f18/p2/multi-threaded/./mergesort 1000 2
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
argc = 3
Breakpoint 1, main (argc=<optimized out>, argv=0x7fffffffcf98) at mergesortTest.c:135
135 struct mergeS *threader = (struct mergeS*) malloc(sizeof(struct mergeS));
Missing separate debuginfos, use: debuginfo-install glibc-2.17-222.el7.x86_64
(gdb) n
137 generate_random_array(B,n,seed);
(gdb)
140 p_start_time = getMilliSeconds();
(gdb)
141 threader[0].numElements = n;
(gdb)
142 threader[0].level = 0;
(gdb)
143 threader[0].Max_Level = Max_Level;
(gdb)
144 threader[0].A = B;
(gdb)
145 pthread_mergesort(threader);
(gdb)
level: 0
for loop
[New Thread 0x7ffff77f1700 (LWP 5892)]
thread failed
for loop
level: 1
for level: 1
join = 0
[New Thread 0x7ffff6ff0700 (LWP 5893)]
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff77f1700 (LWP 5892)]
0x00007ffff7bc7f01 in pthread_join () from /lib64/libpthread.so.0
(gdb)
文件尾
**Valgrind report**
[rutgerluther@onyxnode72 multi-threaded]$ valgrind --leak-check=yes ./mergesort 1000 2
==5636== Memcheck, a memory error detector
==5636== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==5636== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==5636== Command: ./mergesort 1000 2
==5636==
argc = 3
level: 0
for loop
thread failed
for loop
thread failed
error: 0
sorted
Serial: Sorting 1000 elements took 0.00 seconds.
993090 > 163007
i: 500
./mergesort: parallel sorting failed!!!!
==5636==
==5636== HEAP SUMMARY:
==5636== in use at exit: 9,152 bytes in 5 blocks
==5636== total heap usage: 30 allocs, 25 frees, 33,216 bytes allocated
==5636==
==5636== 1,120 bytes in 2 blocks are possibly lost in loss record 2 of 4
==5636== at 0x4C2B9B5: calloc (vg_replace_malloc.c:711)
==5636== by 0x40128C4: _dl_allocate_tls (in /usr/lib64/ld-2.17.so)
==5636== by 0x4E3E7FB: pthread_create@@GLIBC_2.2.5 (in /usr/lib64/libpthread-2.17.so)
==5636== by 0x400E88: pthread_mergesort (mergesort.c:114)
==5636== by 0x400B00: main (mergesortTest.c:145)
==5636==
==5636== LEAK SUMMARY:
==5636== definitely lost: 0 bytes in 0 blocks
==5636== indirectly lost: 0 bytes in 0 blocks
==5636== possibly lost: 1,120 bytes in 2 blocks
==5636== still reachable: 8,032 bytes in 3 blocks
==5636== suppressed: 0 bytes in 0 blocks
==5636== Reachable blocks (those to which a pointer was found) are not shown.
==5636== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==5636==
==5636== For counts of detected and suppressed errors, rerun with: -v
==5636== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
[rutgerluther@onyxnode72 multi-threaded]$
文件尾
我正在运行此命令，只给它提供了1000个元素，并且仅使用了2个线程。虽然此问题仍然发生在任何大于1的线程上。 我已经阅读了手册页，并查看了其他示例和以前的案例，其中我使用了此示例，而同学使用了这些示例。但是我仍然无法弄清楚。
感谢您的帮助。
如果更改了某些内容，则pthread正在正确创建。这是进入功能。我不知道tids [0]的值应该是多少。但是数组中的元素是随机数。
**mergesort.c function call on tids**
level: 1
116 if((error = pthread_create(&tids[i],NULL,pthread_mergesort,(void*)&merger[i])) != 0)
(gdb) info tids
Undefined info command: "tids". Try "help info".
(gdb) print tids[0]
$2 = 140737345689344
(gdb) print &tids
Address requested for identifier "tids" which is in register $r14
(gdb) print *tids
$3 = 140737345689344
(gdb) n
thread failed
for level: 1
join = 0
117 {
(gdb) print tids
$4 = (pthread_t *) 0x604f90
(gdb) print tids[0]
$5 = 140737345689344
(gdb)
答案 0 :(得分：1)
如果未采用分支tids，则if(level < Max_Level - 1)数组将包含未初始化的数据。仅当您成功致电pthread_join时，才需要致电pthread_create。