使用pthread_create（）创建1000多个线程

Question

I'm trying to create 1000 threads using the pthread_create() function.

This is the statement I'm using:

for (int i=0 ; i <1000; i++)
{
   retValue = pthread_create(&threadId, NULL, simplethreadFunction, NULL);
}

Everytime this for-loop runs does it create a new thread?

This is a simple thing. But I'm unable to understand it.

Answer 1

Everytime this for-loop runs does it create a new thread?

Yes, it does.

This is a simple thing. But I'm unable to understand it.

I will add a few more points:

1. First parameter to the function pthread_create is pointer type to pthread_t. Basically you are passing an address to this function, which this function uses to assign 'something'.

   When this function creates a thread, an 'opaque, unique identifier' for this thread is created and the pointer you passed is made to point to this location, so that you can access it later, if required.

2. If you will pass the same pointer all the 1000 times, you will have access to the unique identifier for only one (the last one) thread created out of all 1000, because each time the previous value will get over written.

3. This unique value is required if you would want to perform further operations on a thread (like joining etc).

4. For details about this function and other thread related functions you can go though this and this .

5. Don't forget to call pthread_exit in your main context, otherwise complete program (including the created threads) might terminate even before all your threads would have finished.

Also regarding the time, this thing might not have any effect on time of creation as far as I think, will just reduce the usability of threads you have created. Also, this time you are calculating is not THE time for creating 1000 threads, will depend on lot of other factors like platform/implementation etc.