PTHREAD_GETCONCURRENCY(3P)

💖 PTHREAD_GETCONCURRENCY(3P) 💖

okay bestie, this one's from the POSIX Programmer's Manual ✨ so buckle up, it's a little old-school but we're gonna make it make sense 🫶

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🌸 PROLOG 🌸

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. iykyk — always double-check on your own box, bestie 💅

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✨ NAME ✨

pthread_getconcurrency, pthread_setconcurrency — get and set the level of concurrency

like... how many threads are we letting run loose at once? that's the whole vibe 🧚

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🎀 SYNOPSIS 🎀

#include <pthread.h>

int pthread_getconcurrency(void);
int pthread_setconcurrency(int new_level);

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💜 DESCRIPTION 💜

Unbound threads in a process may or may not be required to be simultaneously active. By default, the threads implementation ensures that a sufficient number of threads are active so that the process can continue to make progress. While this conserves system resources, it may not produce the most effective level of concurrency. lowkey efficient, highkey not always the moment ✨

The pthread_setconcurrency() function allows an application to inform the threads implementation of its desired concurrency level, new_level. The actual level of concurrency provided by the implementation as a result of this function call is unspecified. no promises, bestie, it's giving "hint not homework"

If new_level is zero, it causes the implementation to maintain the concurrency level at its discretion as if pthread_setconcurrency() had never been called.

The pthread_getconcurrency() function shall return the value set by a previous call to the pthread_setconcurrency() function. If the pthread_setconcurrency() function was not previously called, this function shall return zero to indicate that the implementation is maintaining the concurrency level.

A call to pthread_setconcurrency() shall inform the implementation of its desired concurrency level. The implementation shall use this as a hint, not a requirement. literally just a suggestion, it's a soft launch not a contract 💅

If an implementation does not support multiplexing of user threads on top of several kernel-scheduled entities, the pthread_setconcurrency() and pthread_getconcurrency() functions are provided for source code compatibility but they shall have no effect when called. To maintain the function semantics, the new_level parameter is saved when pthread_setconcurrency() is called so that a subsequent call to pthread_getconcurrency() shall return the same value. so it's decorative but consistent, iconic behavior honestly 👑

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🔥 RETURN VALUE 🔥

If successful, the pthread_setconcurrency() function shall return zero; otherwise, an error number shall be returned to indicate the error.

The pthread_getconcurrency() function shall always return the concurrency level set by a previous call to pthread_setconcurrency(). If the pthread_setconcurrency() function has never been called, pthread_getconcurrency() shall return zero.

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💀 ERRORS 💀

The pthread_setconcurrency() function shall fail if:

• EINVAL — The value specified by new_level is negative. girl why is it negative 😭
• EAGAIN — The value specified by new_level would cause a system resource to be exceeded. too much, too fast, the system said no 🫶

The pthread_setconcurrency() function shall not return an error code of [EINTR].

The following sections are informative. (translation: not the legally-binding part, just the helpful gossip ✨)

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🌈 EXAMPLES 🌈

None. literally nothing. empty. void. the silence is deafening 💀

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🦋 APPLICATION USAGE 🦋

Application developers should note that an implementation can always ignore any calls to pthread_setconcurrency() and return a constant for pthread_getconcurrency(). For this reason, it is not recommended that portable applications use this function. bestie, if you want your code to travel well, maybe don't ✋

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⭐ RATIONALE ⭐

None. nothing to explain, it is what it is 🎀

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🙈 FUTURE DIRECTIONS 🙈

These functions may be removed in a future version. they're on thin ice fr fr 😭

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💅 SEE ALSO 💅

The Base Definitions volume of POSIX.1‐2017, <pthread.h>

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👑 COPYRIGHT 👑

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

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and that's the whole page bestie!! brought to you by IEEE/The Open Group, 2017, and the good people at PTHREAD_GETCONCURRENCY(3P) 💖 go set some concurrency (or don't, it's just a hint) and slay ✨🦋