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Wikipedia

pthreads

January 01, 1970

In computing, POSIX Threads, commonly known as pthreads, is an execution model that exists independently from a programming language, as well as a parallel execution model. It allows a program to control multiple different flows of work that overlap in time. Each flow of work is referred to as a thread, and creation and control over these flows is achieved by making calls to the POSIX Threads API. POSIX Threads is an API defined by the Institute of Electrical and Electronics Engineers (IEEE) standard POSIX.1c, Threads extensions (IEEE Std 1003.1c-1995).

Implementations of the API are available on many Unix-like POSIX-conformant operating systems such as FreeBSD, NetBSD, OpenBSD, Linux, macOS, Android,[1] Solaris, Redox, and AUTOSAR Adaptive, typically bundled as a library libpthread. DR-DOS and Microsoft Windows implementations also exist: within the SFU/SUA subsystem which provides a native implementation of a number of POSIX APIs, and also within third-party packages such as pthreads-w32,[2] which implements pthreads on top of existing Windows API.

Contents edit

pthreads defines a set of C programming language types, functions and constants. It is implemented with a pthread.h header and a thread library.

There are around 100 threads procedures, all prefixed pthread_ and they can be categorized into four groups:

The POSIX semaphore API works with POSIX threads but is not part of the threads standard, having been defined in the POSIX.1b, Real-time extensions (IEEE Std 1003.1b-1993) standard. Consequently, the semaphore procedures are prefixed by sem_ instead of pthread_.

Example edit

An example illustrating the use of pthreads in C: 

#include <stdio.h> #include <stdlib.h> #include <assert.h> #include <pthread.h> #include <unistd.h> #define NUM_THREADS 5 void *perform_work(void *arguments){  int index = *((int *)arguments);  int sleep_time = 1 + rand() % NUM_THREADS;  printf("Thread %d: Started.\n", index);  printf("Thread %d: Will be sleeping for %d seconds.\n", index, sleep_time);  sleep(sleep_time);  printf("Thread %d: Ended.\n", index);  return NULL; } int main(void) {  pthread_t threads[NUM_THREADS];  int thread_args[NUM_THREADS];  int i;  int result_code;    //create all threads one by one  for (i = 0; i < NUM_THREADS; i++) {  printf("In main: Creating thread %d.\n", i);  thread_args[i] = i;  result_code = pthread_create(&threads[i], NULL, perform_work, &thread_args[i]);  assert(!result_code);  }  printf("In main: All threads are created.\n");  //wait for each thread to complete  for (i = 0; i < NUM_THREADS; i++) {  result_code = pthread_join(threads[i], NULL);  assert(!result_code);  printf("In main: Thread %d has ended.\n", i);  }  printf("Main program has ended.\n");  return 0; }

This program creates five threads, each executing the function perform_work that prints the unique number of this thread to standard output. If a programmer wanted the threads to communicate with each other, this would require defining a variable outside of the scope of any of the functions, making it a global variable. This program can be compiled using the gcc compiler with the following command: 

gcc pthreads_demo.c -pthread -o pthreads_demo

Here is one of the many possible outputs from running this program. 

In main: Creating thread 0. In main: Creating thread 1. In main: Creating thread 2. In main: Creating thread 3. Thread 0: Started. In main: Creating thread 4. Thread 3: Started. Thread 2: Started. Thread 0: Will be sleeping for 3 seconds. Thread 1: Started. Thread 1: Will be sleeping for 5 seconds. Thread 2: Will be sleeping for 4 seconds. Thread 4: Started. Thread 4: Will be sleeping for 1 seconds. In main: All threads are created. Thread 3: Will be sleeping for 4 seconds. Thread 4: Ended. Thread 0: Ended. In main: Thread 0 has ended. Thread 2: Ended. Thread 3: Ended. Thread 1: Ended. In main: Thread 1 has ended. In main: Thread 2 has ended. In main: Thread 3 has ended. In main: Thread 4 has ended. Main program has ended.

POSIX Threads for Windows edit

Windows does not support the pthreads standard natively, therefore the Pthreads4w project seeks to provide a portable and open-source wrapper implementation. It can also be used to port Unix software (which uses pthreads) with little or no modification to the Windows platform.[4] Pthreads4w version 3.0.0[5] or later, released under the Apache Public License v2.0, is compatible with 64-bit or 32-bit Windows systems. Version 2.11.0,[6] released under the LGPLv3 license, is also 64-bit or 32-bit compatible.

The Mingw-w64 project also contains a wrapper implementation of 'pthreads, winpthreads, which tries to use more native system calls than the Pthreads4w project.[7]

Interix environment subsystem available in the Windows Services for UNIX/Subsystem for UNIX-based Applications package provides a native port of the pthreads API, i.e. not mapped on Win32 API but built directly on the operating system syscall interface.[8]

See also edit

References edit

  1. ^ "libc/bionic/pthread.c - platform/bionic - Git at Google". android.googlesource.com.
  2. ^ . 2006-12-22. Archived from the original on 2010-06-11. Retrieved 2010-08-29.
  3. ^ "pthread.h(0p) — Linux manual page". Retrieved 18 December 2022.
  4. ^ Hart, Johnson M. (2004-11-21). . Archived from the original on 2010-08-30. Retrieved 2010-08-29.
  5. ^ File: pthreads4w-code-v3.0.0.zip – Source for pthreads4w v3.0.0
  6. ^ File: pthreads4w-code-v2.11.0.zip – Source for pthreads4w v2.11.0
  7. ^ see http://locklessinc.com/articles/pthreads_on_windows which is where it was originally derived from
  8. ^ "Chapter 1: Introduction to Windows Services for UNIX 3.5". 5 December 2007.

Further reading edit

  • David R. Butenhof (1997). Programming with POSIX Threads. Addison-Wesley. ISBN 978-0-201-63392-4.
  • Bradford Nichols; Dick Buttlar; Jacqueline Proulx Farell (September 1996). Pthreads Programming. O'Reilly & Associates. ISBN 978-1-56592-115-3.
  • Charles J. Northrup (1996-01-25). Programming with UNIX Threads. John Wiley & Sons. ISBN 978-0-471-13751-1.
  • Kay A. Robbins & Steven Robbins (2003). UNIX Systems Programming. Prentice-Hall. ISBN 978-0-13-042411-2.

External links edit

  • The Open Group Base Specifications Issue 7, IEEE Std 1003.1

January 01, 1970
pthreads, computing, posix, threads, commonly, known, execution, model, that, exists, independently, from, programming, language, well, parallel, execution, model, allows, program, control, multiple, different, flows, work, that, overlap, time, each, flow, wor. In computing POSIX Threads commonly known as pthreads is an execution model that exists independently from a programming language as well as a parallel execution model It allows a program to control multiple different flows of work that overlap in time Each flow of work is referred to as a thread and creation and control over these flows is achieved by making calls to the POSIX Threads API POSIX Threads is an API defined by the Institute of Electrical and Electronics Engineers IEEE standard POSIX 1c Threads extensions IEEE Std 1003 1c 1995 Implementations of the API are available on many Unix like POSIX conformant operating systems such as FreeBSD NetBSD OpenBSD Linux macOS Android 1 Solaris Redox and AUTOSAR Adaptive typically bundled as a library libpthread DR DOS and Microsoft Windows implementations also exist within the SFU SUA subsystem which provides a native implementation of a number of POSIX APIs and also within third party packages such as pthreads w32 2 which implements pthreads on top of existing Windows API Contents 1 Contents 2 Example 3 POSIX Threads for Windows 4 See also 5 References 6 Further reading 7 External linksContents editpthreads defines a set of C programming language types functions and constants It is implemented with a pthread h header and a thread library There are around 100 threads procedures all prefixed pthread and they can be categorized into four groups Thread management creating joining threads etc Mutexes Condition variables Synchronization between threads using read write locks and barriers Spinlocks 3 The POSIX semaphore API works with POSIX threads but is not part of the threads standard having been defined in the POSIX 1b Real time extensions IEEE Std 1003 1b 1993 standard Consequently the semaphore procedures are prefixed by sem instead of pthread Example editAn example illustrating the use of pthreads in C include lt stdio h gt include lt stdlib h gt include lt assert h gt include lt pthread h gt include lt unistd h gt define NUM THREADS 5 void perform work void arguments int index int arguments int sleep time 1 rand NUM THREADS printf Thread d Started n index printf Thread d Will be sleeping for d seconds n index sleep time sleep sleep time printf Thread d Ended n index return NULL int main void pthread t threads NUM THREADS int thread args NUM THREADS int i int result code create all threads one by one for i 0 i lt NUM THREADS i printf In main Creating thread d n i thread args i i result code pthread create amp threads i NULL perform work amp thread args i assert result code printf In main All threads are created n wait for each thread to complete for i 0 i lt NUM THREADS i result code pthread join threads i NULL assert result code printf In main Thread d has ended n i printf Main program has ended n return 0 This program creates five threads each executing the function perform work that prints the unique number of this thread to standard output If a programmer wanted the threads to communicate with each other this would require defining a variable outside of the scope of any of the functions making it a global variable This program can be compiled using the gcc compiler with the following command gcc pthreads demo c pthread o pthreads demo Here is one of the many possible outputs from running this program In main Creating thread 0 In main Creating thread 1 In main Creating thread 2 In main Creating thread 3 Thread 0 Started In main Creating thread 4 Thread 3 Started Thread 2 Started Thread 0 Will be sleeping for 3 seconds Thread 1 Started Thread 1 Will be sleeping for 5 seconds Thread 2 Will be sleeping for 4 seconds Thread 4 Started Thread 4 Will be sleeping for 1 seconds In main All threads are created Thread 3 Will be sleeping for 4 seconds Thread 4 Ended Thread 0 Ended In main Thread 0 has ended Thread 2 Ended Thread 3 Ended Thread 1 Ended In main Thread 1 has ended In main Thread 2 has ended In main Thread 3 has ended In main Thread 4 has ended Main program has ended POSIX Threads for Windows editWindows does not support the pthreads standard natively therefore the Pthreads4w project seeks to provide a portable and open source wrapper implementation It can also be used to port Unix software which uses pthreads with little or no modification to the Windows platform 4 Pthreads4w version 3 0 0 5 or later released under the Apache Public License v2 0 is compatible with 64 bit or 32 bit Windows systems Version 2 11 0 6 released under the LGPLv3 license is also 64 bit or 32 bit compatible The Mingw w64 project also contains a wrapper implementation of pthreads winpthreads which tries to use more native system calls than the Pthreads4w project 7 Interix environment subsystem available in the Windows Services for UNIX Subsystem for UNIX based Applications package provides a native port of the pthreads API i e not mapped on Win32 API but built directly on the operating system syscall interface 8 See also editRuntime system OpenMP Cilk Cilk Plus Threading Building Blocks TBB Native POSIX Thread Library NPTL DCEThreads clone Linux system call Spurious wakeup Thread local storage GNU Portable Threads Grand Central Dispatch Apple s thread library Beginthread a subroutine within Windows for creating a new thread and Unix thread State Threads an event driven approach to threadingReferences edit libc bionic pthread c platform bionic Git at Google android googlesource com Pthread Win 32 Level of standards conformance 2006 12 22 Archived from the original on 2010 06 11 Retrieved 2010 08 29 pthread h 0p Linux manual page Retrieved 18 December 2022 Hart Johnson M 2004 11 21 Experiments with the Open Source Pthreads Library and Some Comments Archived from the original on 2010 08 30 Retrieved 2010 08 29 File pthreads4w code v3 0 0 zip Source for pthreads4w v3 0 0 File pthreads4w code v2 11 0 zip Source for pthreads4w v2 11 0 see http locklessinc com articles pthreads on windows which is where it was originally derived from Chapter 1 Introduction to Windows Services for UNIX 3 5 5 December 2007 Further reading editDavid R Butenhof 1997 Programming with POSIX Threads Addison Wesley ISBN 978 0 201 63392 4 Bradford Nichols Dick Buttlar Jacqueline Proulx Farell September 1996 Pthreads Programming O Reilly amp Associates ISBN 978 1 56592 115 3 Charles J Northrup 1996 01 25 Programming with UNIX Threads John Wiley amp Sons ISBN 978 0 471 13751 1 Kay A Robbins amp Steven Robbins 2003 UNIX Systems Programming Prentice Hall ISBN 978 0 13 042411 2 External links editThe Open Group Base Specifications Issue 7 IEEE Std 1003 1 Retrieved from https en wikipedia org w index php title Pthreads amp oldid 1218075891, wikipedia, wiki, book, books, library,

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