pthread_setconcurrency(3) [freebsd man page]

PTHREAD_GETCONCURRENCY(3)				   BSD Library Functions Manual 				 PTHREAD_GETCONCURRENCY(3)

NAME

     pthread_getconcurrency, pthread_setconcurrency -- get or set level of concurrency

LIBRARY

     POSIX Threads Library (libpthread, -lpthread)

SYNOPSIS

     #include <pthread.h>

     int
     pthread_getconcurrency(void);

     int
     pthread_setconcurrency(int new_level);

DESCRIPTION

     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.  If new_level is zero, it
     causes the implementation to maintain the concurrency level at its discretion as if pthread_setconcurrency() was never called.  The
     pthread_getconcurrency() function returns the value set by a previous call to the pthread_setconcurrency() function.  If the
     pthread_setconcurrency() function was not previously called, this function returns zero to indicate that the implementation is maintaining
     the concurrency level.  When an application calls pthread_setconcurrency(), it is informing the implementation of its desired concurrency
     level.  The implementation uses this as a hint, not a requirement.

RETURN VALUES

     If successful, the pthread_setconcurrency() function returns zero.  Otherwise, an error number is returned to indicate the error.	The
     pthread_getconcurrency() function always returns the concurrency level set by a previous call to pthread_setconcurrency().  If the
     pthread_setconcurrency() function has never been called, pthread_getconcurrency() returns zero.

ERRORS

     The pthread_setconcurrency() function will fail if:

     [EINVAL]		The value specified by new_level is negative.

     [EAGAIN]		The value specified by new_level would cause a system resource to be exceeded.

APPLICATION USAGE

     Use of these functions changes the state of the underlying concurrency upon which the application depends.  Library developers are advised to
     not use the pthread_getconcurrency() and pthread_setconcurrency() functions since their use may conflict with an application's use of these
     functions.

STANDARDS

     The pthread_getconcurrency() and pthread_setconcurrency() functions conform to Version 2 of the Single UNIX Specification (``SUSv2'').

BSD
								  April 11, 2003							       BSD

pthread_getconcurrency(3C)				   Standard C Library Functions 				pthread_getconcurrency(3C)

NAME

       pthread_getconcurrency, pthread_setconcurrency - get or set level of concurrency

SYNOPSIS

       cc -mt [ flag... ] file... -lpthread [ library... ]
       #include <pthread.h>

       int pthread_getconcurrency(void);

       int pthread_setconcurrency(int new_level);

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.

       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.

       If new_level is	0, it causes the implementation to maintain the concurrency level at its discretion  as  if  pthread_setconcurrency()  was
       never called.

       The   pthread_getconcurrency()  function  returns  the	value  set  by	a  previous call to the  pthread_setconcurrency() function. If the
       pthread_setconcurrency() function was not previously called, this function returns  0 to indicate that the  implementation  is  maintaining
       the concurrency level.

       When an application calls  pthread_setconcurrency() it is informing the implementation of its desired concurrency level. The implementation
       uses this as a hint, not a requirement.

       If an implementation does not support multiplexing of user threads on top of several kernel  scheduled  entities,  the	pthread_setconcur-
       rency() and  pthread_getconcurrency() functions will be provided for source code compatibility but they will have no effect when called. To
       maintain the function semantics, the new_level parameter will be saved when  pthread_setconcurrency() is called so that a  subsequent  call
       to pthread_getconcurrency() returns the same value.

RETURN VALUES

       If successful, the  pthread_setconcurrency() function returns  0. Otherwise, an error number is returned to indicate the error.

       The   pthread_getconcurrency()  function  always  returns the concurrency level set by a previous call to  pthread_setconcurrency(). If the
       pthread_setconcurrency() function has never been called,  pthread_getconcurrency() returns  0.

ERRORS

       The pthread_setconcurrency() function will fail if:

       EINVAL	 The value specified by new_level is negative.

       EAGAIN	 The value specific by new_level would cause a system resource to be exceeded.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       pthread_create(3C), pthread_attr_init(3C), attributes(5), standards(5)

SunOS 5.11							    23 Mar 2005 					pthread_getconcurrency(3C)