


C language multithreaded programming: a beginner's guide and troubleshooting
Apr 04, 2025 am 10:15 AMC Language Multithreading Programming Guide: Creating Threads: Use the pthread_create() function to specify thread ID, properties, and thread functions. Thread synchronization: Prevent data competition through mutexes, semaphores, and conditional variables. Practical case: Use multi-threading to calculate the Fibonacci number, assign tasks to multiple threads and synchronize the results. Troubleshooting: Solve problems such as program crashes, thread stop responses, and performance bottlenecks.
C Language Multithreaded Programming: A Newbie Guide and Troubleshooting
introduction
Multithreaded programming is a powerful technology that allows programs to perform multiple tasks in parallel. In C, multithreading is implemented using the POSIX threading library. This article will provide a guide to multithreaded programming for beginners in C languages ??and answer some common difficult questions.
Create and run threads
To create a thread, you need to call pthread_create()
function. It requires three parameters:
- Thread ID : A pointer to save the newly created thread ID
- Thread properties : Specify properties such as thread stack size and priority
- Thread function : a function to be executed by a thread
The following code creates a thread called my_thread()
:
#include <pthread.h> void *my_thread(void *arg) { // The code executed by the thread is returned NULL; } int main() { pthread_t thread_id; pthread_create(&thread_id, NULL, my_thread, NULL); pthread_join(thread_id, NULL); // Wait for the thread to complete return 0; }
Thread synchronization
When multiple threads access shared resources, synchronization is required to avoid data race. This can be achieved by:
- Mutex : Restricts only one thread to access shared resources at the same time.
- Semaphore : allows multiple threads to access shared resources at the same time, but limits the number of threads to access resources.
- Condition variable : allows threads to wait for a specific condition to be satisfied.
Practical cases
The following is a practical case of using multithreading to calculate Fibonacci sequences:
#include <pthread.h> #define NUM_THREADS 4 #define MAX_NUMBER 100 int fib_numbers[MAX_NUMBER]; void *calculate_fib_numbers(void *arg) { int start = (int) arg; int end = start NUM_THREADS - 1; for (int i = start; i <= end; i ) fib_numbers[i] = fib(i); return NULL; } int main() { pthread_t threads[NUM_THREADS]; for (int i = 0; i < NUM_THREADS; i ) pthread_create(&threads[i], NULL, calculate_fib_numbers, (void *) (i * NUM_THREADS)); for (int i = 0; i < NUM_THREADS; i ) pthread_join(threads[i], NULL); // Print result for (int i = 0; i < MAX_NUMBER; i ) printf("%d", fib_numbers[i]); return 0; }
Troubleshooting
- The program crashes with the error "segment fault" : It may be that the memory area that the thread does not own. Make sure to use mutexes or other synchronization mechanisms to protect shared resources.
- Thread stops responding : It may be an infinite loop or other deadlock situation. Try to use a debugger or logging to find out the cause of the deadlock.
- Thread execution is too slow : it may be due to competition among threads or other performance bottlenecks. Try benchmarking the code and find out the slower points.
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