Questions and Answers
What is the primary assumption of Pthreads library?
What is the purpose of the pthread_attr_t
argument in the pthread_create
function?
What is the return type of the start_routine
function in Pthreads?
What is the purpose of the pthread_join
function?
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What is the linker option required to compile a Pthreads program?
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What is the purpose of the thread_p
argument in the pthread_create
function?
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How does the Increment
function in the example application divide the work among threads?
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What is the purpose of the arg_p
argument in the pthread_create
function?
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What is the effect of calling pthread_join
on the main thread?
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What is the common operating system requirement for Pthreads to work?
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What is the purpose of including the library headers in a Pthreads program?
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What is the type of the 'start_routine' function argument in the pthread_create function?
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What is the output of the 'printf' statement in the 'Increment' function?
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What is the purpose of the 'my_n' variable in the 'Increment' function?
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What is the effect of the 'my_first_i' and 'my_last_i' variables in the 'Increment' function?
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What is the purpose of the 'gcc -lpthread hello.c -o hello' command?
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What is the type of the 'thread_p' argument in the pthread_create function?
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What is the purpose of the 'n' variable in the example application?
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What is the purpose of the 'sum' variable in the example application?
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Study Notes
Introduction to Pthreads
- Pthreads is a library for developing parallel applications using shared memory.
- It assumes a POSIX-compliant operating system as its base.
- The library can be embedded in any programming language, usually C.
Compilation and Execution of Pthreads Programs
- To compile a Pthreads program, include the library headers using
#include
. - Use the linker option
-lpthread
to link the program with the Pthreads library. - Example compilation command:
gcc -lpthread hello.c -o hello
.
Pthread API to Create and Join Threads
- The
pthread_create
function is used to create a new thread:-
pthread_t* thread_p
: thread object reference -
const pthread_attr_t* attr_p
: creation attributes (can beNULL
) -
void* (*start_routine)(void*)
: function to execute -
void* arg_p
: function argument
-
- The
pthread_join
function is used to wait for a thread to finish:-
pthread_t thread
: thread to wait for -
void** ret_val_p
: return value of the thread
-
Thread Function Header
- The header for a thread function is
void* start_routine(void* args_p);
.
Example Incremental Application
- The example application uses global variables:
-
long long n
: number of iterations -
long long thread_count
: number of threads -
long long sum
: global sum value
-
- The
Increment
function is executed by each thread:-
void* Increment(void* rank)
: function to increment the global sum - The function calculates its own range of iteration based on the thread rank and number of threads.
-
Pthreads Overview
- Pthreads is a library for developing parallel applications using shared memory.
- It assumes a POSIX-compliant operating system as its base.
- The library can be embedded in any programming language, usually C.
Compilation and Execution of Pthreads Programs
- To compile a Pthreads program, include the library headers with
#include
. - Use the linker option
-lpthread
to link the program. - Example compilation command:
gcc -lpthread hello.c -o hello
.
Pthread API
Thread Creation
- The
pthread_create
function creates a new thread:-
pthread_t* thread_p
: thread object reference -
const pthread_attr_t* attr_p
: creation attributes (can beNULL
) -
void* (*start_routine)(void*)
: function to execute -
void* arg_p
: function argument
-
- Generic function header for the
start_routine
:void* start_routine(void* args_p);
Thread Joining
- The
pthread_join
function waits for a thread to terminate:-
pthread_t thread
: thread to join -
void** ret_val_p
: return value of the thread (can beNULL
)
-
Example Incremental Application
- The example application demonstrates thread creation and synchronization.
- Global variables:
-
long long n
: number of iterations -
long long thread_count
: number of threads -
long long sum
: global sum value
-
- The
Increment
function is the thread operation:- Each thread calculates its range of iterations based on its rank.
- The thread prints its range and then increments the global sum.
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Description
Explore the Pthreads library for developing parallel applications using shared memory, including compilation and execution of Pthreads programs.