Pthreads Error "_imp_pthread_create"

[Nico N]

Hey Guys,
I've learned programming in C in school for about one yearand a half and now I wanted to try myself in parallel programming. I downloaded the Pthread-files and tried to write a sorting program with and without pthreads to compare how fast they are. But when I try to compile my parallel program I get two errors I don't understand:
"undefined reference to _imp_pthread_create"
"undefined reference to _imp_pthread_join"
I can't find any mistakes in my program, maybe anyone of you can help me. This is my Program:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>

void *DieOberen50000 (int a[100000])
{
	int i,j,h,m;
	for (i=100000;i>=50000;i--)
	{
		m=i;
		for (j=0;j<=i;j++)
		{
			if (a[j]>a[m])
			{
				m=j;
			}
		}
		h=a[m];
		a[m]=a[i];
		a[i]=h;
	}
}

void *DieUnteren50000(int a[100000])
{
	int i,j,h,m;
	for (i=0;i<=50000;i++)
	{
		m=i;
		for (j=i;j<=100000;j++)
		{
			if (a[j]<a[m])
			{
				m=j;
			}
		}
		h=a[m];
		a[m]=a[i];
		a[i]=h;

	}
}

void main()
{
	int rc,i,a[100000];
	void *valuep;
	time_t seconds;
	pthread_t *Schleife1,*Schleife2;

	srand(time(NULL));

	for (i=0;i<100000;i++)
	{
		a[i]=rand() % 10000;
		printf("%d ",a[i]);
	}

	printf("\n\n");

	seconds = time (NULL);

	rc = pthread_create(Schleife1,NULL,DieOberen50000, a);
	rc = pthread_create(Schleife2,NULL,DieUnteren50000,a);
	rc = pthread_join (*Schleife1,&valuep);
	rc = pthread_join (*Schleife2,&valuep);

	for (i=0;i<100000;i++)
	{
		printf("%d ",a[i]);
	}


	seconds = time(NULL) - seconds;

	printf("\n\n %ld", seconds);


	scanf("%d",i);
}

PS: I'm using lcc-win32 on Windows Vista.

[Salem]

Well you need to add the pthread library (for how, read your compiler manual).

Something like
cc prog.c -lpthread

Problems with your code
1. main returns int, not void.
2. scanf("%d",i); needs to be scanf("%d",&i);
3. DieOberen50000 starts off 1 element past the end of the array
4. Both functions modify the same middle element.

[Nico N]

Sorry I cant find it in the manual. Please explain to me how to add the library. Furthermore I dont have the prog.cc file, it wasn't in the Pthreads directory I downloaded:
ftp://sourceware.org/pub/pthreads-win32/

[Salem]

1. prog.c is whatever YOU called your source file.

2. Adding the library should be described in the manual for your lcc-win32 compiler.
I don't have that compiler installed, so I can't help you with that.