Systems Programming Homework

Homework 5

For this assignment, base your solution on the following skeleton code::

#include <stdlib.h> #include <stdio.h> #include <pthread.h> #define NUM_WORKER_THREADS 500

struct thread_data { pthread_t tid; unsigned int num;

};

struct workers_state { int still_working; pthread_mutex_t mutex; pthread_cond_t signal;

};

static struct workers_state wstate = { .still_working = NUM_WORKER_THREADS, .mutex = PTHREAD_MUTEX_INITIALIZER, .signal = PTHREAD_COND_INITIALIZER

};

static unsigned int result[NUM_WORKER_THREADS];

void* worker_thread (void* param) {

}

int main (int argc, char** argv) {

}

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The main function shall:

1. Dynamically allocate NUM_WORKER_THREADS (i.e. 500) struct thread_data structures onto the heap.

• Store the starting memory address of where these structures live in the heap into a variable named threads.

• Individual struct thread_data structures should be accessible using array notation (e.g. threads[i])

2. Assign a number to each worker thread.

• A worker thread’s number is an integer between 0 and NUM_WORKER_THREADS-1. • Each worker thread’s number should be unique. • A worker thread’s number is used to index into the array threads[] to get its thread_data structure.

• A thread’s number should be stored into the num member of its thread_data structure.

3. Create NUM_WORKER_THREADS worker threads.

• Each worker thread should start in the function worker_thread() • An individual worker thread’s thread_data structure should be passed as the parameter to

worker_thread() during thread creation. • The Thread ID provided by pthread_create() during the thread creation process should be directly stored into the tid member of the thread’s personal thread_data structure.

• Worker threads should be in a detached state

4. Check if all worker threads have completed by checking the value of the still_working member of the wstate structure located in the DATA segment.

• The main thread should check for this using the provided condition variable signal

5. Free the struct thread_data structures that were allocated onto the heap once they are no longer necessary.

6. Sum all of the elements of the global array result[] into a local variable named total.

7. Print the value of total to the screen.

Each worker thread shall:

1. Square their thread number and store the result into the global array result[]

• Access to the global array result[] should be indexed by a worker thread’s number

2. Decrement the variable still_working, which is a member of wstate.

3. Notify any threads that may be waiting for the state of still_working to change.

Additionally, after total has been printed to the screen, your main function should perform the following computation for C using a single thread (this is easily accomplished with a for-loop):

C = ∑499

i=0 i 2

Print the value of C to the screen as a check to see if total was computed properly in your multi-threaded approach.

Upload your code to BBLearn as a single C file named abc123_hw4.c

(Again, replace abc123 with your Drexel ID)

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