Pemrograman Paralel @2012,Eko Didik Widianto …didik.blog.undip.ac.id/files/2012/02/TSK617-Kuliah5-Pemrograman_P... · Pemrograman Paralel dengan PThread @2012,Eko Didik Widianto

Pemrograman Paraleldengan PThread

@2012,Eko DidikWidianto

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LisensiPemrograman Paralel dengan PThreadKuliah#5 TSK205 Sistem Digital - TA 2011/2012

Eko Didik Widianto

Teknik Sistem Komputer - Universitas Diponegoro



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Tentang Kuliah

I Sebelumnya dibahas tentang:I Desain model pemrograman di atas mesin memori bersama

(misalnya SMP/symetric multiprocessor) menggunakanthread

I Posix Thread/Pthread: menggunakan pustaka untukparalelisme

I OpenMP: menggunakan compiler directive untuk paralelisme

I Dalam kuliah ini, akan dibahas pemrogramanmenggunakan pustaka Posix Thread

I Pustaka PthreadI API PthreadI Mengkompile program multithreadI Mengelola ThreadI Variabel MutexI Variabel Kondisional



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Kompetensi Dasar

I Setelah mempelajari bab ini, mahasiswa akan mampu:1. [C3] Mahasiswa akan mampu mengaplikasikan rutin-rutin

pustaka pthread untuk memprogram paralel berbasis thread2. [C4] Mahasiswa akan mampu memprogram suatu aplikasi

berbasis pthread sesuai dengan kebutuhan desain

I AcknowledmentMateri dan gambar didapat dari:

I POSIX Threads Programming dihttps://computing.llnl.gov/tutorials/pthreads/

I LinkI Website: http://didik.blog.undip.ac.id/2012/02/25/

kuliah-tsk-617-pengolahan-paralel-2011/I Email: [email protected]

https://computing.llnl.gov/tutorials/pthreads/

http://didik.blog.undip.ac.id/2012/02/25/kuliah-tsk-617-pengolahan-paralel-2011/

http://didik.blog.undip.ac.id/2012/02/25/kuliah-tsk-617-pengolahan-paralel-2011/

mailto:[email protected]



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POSIX ThreadKonsep ThreadTentang POSIX Threads

API PThreadAPI PThreadCreating and Terminating ThreadPassing Argumen ke ThreadJoining dan Detaching Thread

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POSIX ThreadKonsep Thread

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Apa itu Thread?

I Secara teknis, sebuah thread didefinisikan sebagai satualiran instruksi yang independen yang dapat dijalankansecara terjadwal oleh OS

I Dapat dibayangkan seperti konsep "procedure" yang dapatberjalan independen dari program utamanya

I Seperti program utama (a.out) yang berisi sejumlahprosedur/fungsi. Kemudian semua prosedur dapat dijadwaluntuk dijalankan secara simultan dan/atau independen olehOS

I Ini menggambarkan program “multi-thread”I Bagaimana menjalankannya secara simultan?





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Process

I Sebuah proses dibuat oleh OS dan memerlukanoverhead untuk menyimpan informasi tentang resourcedan state eksekusi program

I Process ID, process group ID, user ID, and group IDI EnvironmentI Working directoryI Program instructionsI RegistersI StackI HeapI File descriptorsI Signal actionsI Shared librariesI Inter-process communication tools (such as message

queues, pipes, semaphores, or shared memory)





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UNIX Process





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Thread dalam Sebuah Proses UNIX





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ThreadI Exists within a process and uses the process resources

I Changes made by one thread to shared system resourceswill be seen by all other threads

I such as closing a fileI Two pointers having the same value point to the same dataI Reading and writing to the same memory locations is

possible, and therefore requires explicit synchronizationby the programmer

I Has its own independent flow of control as long as its parentprocess exists

I Stack pointer, registers, scheduling properties (such aspolicy or priority), set of pending and blocked signals, threadspecific data.

I Duplicates only the essential resources it needs to beindependently schedulable

I May share the process resources with other threads that actequally independently (and dependently)

I Dies if the parent process dies - or something similarI Is "lightweight" because most of the overhead has already been

accomplished through the creation of its process





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POSIX Thread

I POSIX: Portable Operating System Interface for UNIXI IEEE Std 1003.1c-1995 mendefinisikan API untuk membuat

dan memanipulasi threadI System call untuk membuat dan mensinkronkan threadI Implementasi API: FreeBSD, NetBSD, GNU/Linux, Mac OS

X dan SolarisI Windows? pthreads-w32 (third party)

I Support PThreadI Membuat program paralelI SinkronisasiI Memori shared implisit, pointer ke data shared diberikan ke

suatu thread

I Implementasi: pthread.h, libpthreadI Some useful links:

I standards.ieee.org/findstds/standard/1003.1-2008.htmlI www.opengroup.org/austin/papers/posix_faq.htmlI www.unix.org/version3/ieee_std.html





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Mengapa PThread?

I The primary motivation is to realize potential programperformance gains

I When compared to the cost of creating and managing aprocess, a thread consumes much less operating systemoverhead

I Managing threads requires fewer system resources thanmanaging processes

I Function:I fork() subroutine: creating a new processI pthread_create() subroutine: creating a new thread





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Fork vs ThreadI All threads within a process share the same address

spaceI Inter-thread communication is more efficient and easier to

use than inter-process communication

Timings reflect 50,000 process/thread creations





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Aplikasi Single-Thread vs Multi-Thread

I Offers potential performance gains and practicaladvantages

I Overlapping CPU work with I/OI For example, a program may have sections where it is

performing a long I/O operation. While one thread is waitingfor an I/O system call to complete, CPU intensive work can beperformed by other threads

I Priority/real-time scheduling: tasks which are moreimportant can be scheduled to supersede or interrupt lowerpriority tasks

I Asynchronous event handling: tasks which service events ofindeterminate frequency and duration can be interleaved

I For example, a web server can both transfer data fromprevious requests and manage the arrival of new requests





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Pthread di Komputer SMP

I To achieve optimum performanceI Performance of an application can be greatly improved by

using Pthread on-node data transfer/communication,instead of using MPI

I MPI libraries usually implement on-node task communicationvia shared memory, which involves at least one memory copyoperation (process to process)

I For Pthreads there is no intermediate memory copy requiredbecause threads share the same address space within asingle processIt becomes more of a cache-to-CPU or memory-to-CPUbandwidth (worst case) situation. These speeds are muchhigher





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Perbandingan Pthread vs MPI di KomputerSMP





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Desain Program MultithreadI On modern, multi-cpu machines, pthreads are ideally

suited for parallel programmingI whatever applies to parallel programming in general, applies

to parallel pthreads programsI In order for a program to take advantage of Pthreads, it

must be able to be organized into discrete, independenttasks which can execute concurrently

I Routines can be interchanged, interleaved and/oroverlapped in real time





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Program yang Akan Memerlukan Pthread

I Programs having the following characteristics may be wellsuited for pthreads:

I Work that can be executed, or data that can be operated on,by multiple tasks simultaneously

I Block for potentially long I/O waitsI Use many CPU cycles in some places but not othersI Must respond to asynchronous eventsI Some work is more important than other work (priority

interrupts)





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Model Program Multithread

I Manager/worker: a single thread, the manager assignswork to other threads, the workers

I Typically, the manager handles all input and parcels outwork to the other tasks.

I At least two forms of the manager/worker model arecommon: static worker pool and dynamic worker pool

I Pipeline: a task is broken into a series of suboperations,each of which is handled in series, but concurrently, by adifferent thread. An automobile assembly line bestdescribes this model.

I Peer: similar to the manager/worker model, but after themain thread creates other threads, it participates in thework





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Model Memori BersamaI All threads have access to the same global, shared

memoryI Threads also have their own private dataI Programmers are responsible for synchronizing access

(protecting) globally shared data





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Thread-safeness

I Thread-safeness: refers an application’s ability to executemultiple threads simultaneously without "clobbering"shared data or creating "race" conditions.

I If the routine does not employ synchronization constructs toprevent data corruption, then it is not thread-safe



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Creating and TerminatingThread

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Joining dan DetachingThread

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POSIX Thread





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API PThreadI Pthreads API was defined in the ANSI/IEEE POSIX 1003.1 -

1995 standardI The subroutines which comprise the Pthreads API can be

informally grouped into:1. Thread management: Routines that work directly on

threads - creating, detaching, joining, etcI Also include functions to set/query thread attributes

(joinable, scheduling etc.)2. Mutexes: Routines that deal with synchronization, called a

"mutex", which is an abbreviation for "mutual exclusion"I Provide for creating, destroying, locking and unlocking

mutexesI Supplemented by mutex attribute functions that set or

modify attributes associated with mutexes3. Condition variables: Routines that address

communications between threads that share a mutex.I Based upon programmer specified conditionsI Includes functions to create, destroy, wait and signal

based upon specified variable values. Functions toset/query condition variable attributes are also included

4. Synchronization: Routines that manage read/write locksand barriers



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Kompilasi dan Linking



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Rutin

I pthread_create (thread,attr,start_routine,arg)I pthread_exit (status)I pthread_cancel (thread)I pthread_attr_init (attr)I pthread_attr_destroy (attr)



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Membuat ThreadRutin: pthread_create (thread,attr,start_routine,arg)

I Argument:I thread: An opaque, unique identifier for the new thread

returned by the subroutineI attr: An opaque attribute object that may be used to set

thread attributes. You can specify a thread attributes object,or NULL for the default values

I start_routine: the C routine that the thread will execute onceit is created

I arg: A single argument that may be passed to start_routine.It must be passed by reference as a pointer cast of typevoid. NULL may be used if no argument is to be passed

I Return: thread_id



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Membuat Thread

I Once created, threads are peers, and may create otherthreads



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Atribut Thread

I Can be set when creating a threadI Or initialize thread attribute in main thread:

pthread_attr_init and pthread_attr_destroyI Attributes:

I Detached or joinable stateI Scheduling inheritanceI Scheduling policyI Scheduling parametersI Scheduling contention scopeI Stack sizeI Stack addressI Stack guard (overflow) size



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Terminasi ThreadRoutine: pthread_exit (status)

I A thread may be terminated:I The thread returns normally from its starting routine. It’s

work is doneI The thread makes a call to the pthread_exit subroutine -

whether its work is done or notI The thread is canceled by another thread via the

pthread_cancel routineI The entire process is terminated due to making a call to

either the exec() or exit()I If main() finishes first, without calling pthread_exit explicitly

itself

I Optional termination status can be specifiedI Typically returned to threads joining the terminated thread

I Cleanup: the pthread_exit() doesnot close filesI Any files opened inside the thread will remain open after the

thread is terminated



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Contoh Kode: Pembuatan dan TerminasiThread

See code



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Passing Argumen ke Thread

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Joining dan Detaching Thread

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I Yang telah kita pelajari hari ini:I tbd

I Yang akan kita pelajari di pertemuan berikutnya adalah<tbd>

I Pelajari: tbd



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Lisensi

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dan menyebarkan karya, danI untuk Remix — untuk mengadaptasikan karya

I Di bawah persyaratan berikut:I Atribusi — Anda harus memberikan atribusi karya sesuai

dengan cara-cara yang diminta oleh pembuat karyatersebut atau pihak yang mengeluarkan lisensi.

I Pembagian Serupa — Jika Anda mengubah, menambah,atau membuat karya lain menggunakan karya ini, Andahanya boleh menyebarkan karya tersebut hanya denganlisensi yang sama, serupa, atau kompatibel.

I Lihat: Creative Commons Attribution-ShareAlike 3.0Unported License

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Pemrograman Paralel @2012,Eko Didik Widianto …didik.blog.undip.ac.id/files/2012/02/TSK617-Kuliah5-Pemrograman_P... · Pemrograman Paralel dengan PThread @2012,Eko Didik Widianto

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