Professor: Shu-Ching Chen TA: Hsin-Yu Ha
An independent stream of instructions that can be scheduled to run A path of execution
int a, b; int c; a = 1; b = a + 2; c = 3; int a, b; a = 1; b = a + 2; int c; c = 5; CPU CPU
Program An execution file stored in the harddrive Process An execution file stored in the Memory Thread An execution path of part of the process
Program Process Memory HDD Thread
Parallel execution Shared resources Easier to create and destroy than processes (100X) Easy porting to multiple CPUs
Standardized C language threads programming interface for UNIX systems Four major groups Thread management: Routines that work directly on threads - creating, detaching, joining, etc. Mutex: Routines that deal with synchronization. Mutex functions provide for creating, destroying, locking and unlocking mutexes.
Condition variable: Routines that address communications between threads that share a mutex.
Synchronization: Routines that manage read/write locks and barriers.
pthread_create() on error Return 0 if OK, nonzero ▪ ▪ ▪ ▪ Four Arguments Thread : A thread identifier Attr : A pointer to a thread attribute object Start_routine : A pointer to the function the thread executes Arg : The argument to the function
pthread_exit() error Return 0 if OK, nonzero on Four ways of terminating a thread The thread returns from its starting routine The thread makes a call to the pthread_exit subroutine The thread is canceled by another thread The entire process is terminated If main() finishes first, without calling pthread_exit
Example of pthread_exit()
pthread_join() error Return 0 if OK, nonzero on Wait from other threads to terminate by calling it
pthread_self() It returns the unique, system assigned thread ID of the calling thread pthread_detach() Return 0 if OK, nonzero on error It can be used to explicitly detach a thread
Join Mutexes Condition variables
Mutexes are used to prevent data inconsistencies due to operations by multiple threads upon the same memory area performed at the same time to prevent race conditions where an order of operation upon the memory is expected
Condition variables are used to allow threads to synchronize based upon the actual value of data without continually polling to check whether the condition if met in conjunction with a mutex lock
POSIX Threads Programming https://computing.llnl.gov/tutorials/pthreads/ Pthreads primer http://pages.cs.wisc.edu/~travitch/pthreads_prim er.html
POSIX thread (pthread) Tutorial
http://en.wikibooks.org/wiki/C%2B%2B_Programming/Threading Tutorial and sample code
Posix threads C
http://codebase.eu/tutorial/posix-threads-c/ http://www.codeproject.com/Articles/14746/Multithreading-Tutorial Tutorial Youtube Video -
C++ Multithreading Pt. 1
C++ Multithreading Pt. 2