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| author | rpj <rpj> | 2005-05-06 07:27:10 +0000 |
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| committer | rpj <rpj> | 2005-05-06 07:27:10 +0000 |
| commit | 7523c7c4d75652f67cd31cb123e1268790394c8b (patch) | |
| tree | 0920ebf089ccb971e0878542f85486171a541a8a /manual/pthread_setconcurrency.html | |
| parent | cf42850c77554311e62d3780f6a36cbc38e5e002 (diff) | |
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diff --git a/manual/pthread_setconcurrency.html b/manual/pthread_setconcurrency.html new file mode 100644 index 0000000..cdd4f58 --- /dev/null +++ b/manual/pthread_setconcurrency.html @@ -0,0 +1,155 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> +<HTML> +<HEAD> + <META HTTP-EQUIV="CONTENT-TYPE" CONTENT="text/html; charset=utf-8"> + <TITLE>"PTHREAD_GETCONCURRENCY"(P) manual page</TITLE> + <META NAME="GENERATOR" CONTENT="OpenOffice.org 1.1.3 (Linux)"> + <META NAME="CREATED" CONTENT="20050505;19162600"> + <META NAME="CHANGED" CONTENT="20050505;19223800"> + <!-- manual page source format generated by PolyglotMan v3.2, --> + <!-- available at http://polyglotman.sourceforge.net/ --> +</HEAD> +<BODY LANG="en-GB" BGCOLOR="#ffffff" DIR="LTR"> +<H4>POSIX Threads for Windows – REFERENCE - <A HREF="http://sources.redhat.com/pthreads-win32">Pthreads-w32</A></H4> +<P><A HREF="index.html">Reference Index</A></P> +<P><A HREF="#toc">Table of Contents</A></P> +<H2><A HREF="#toc0" NAME="sect0">Name</A></H2> +<P>pthread_getconcurrency, pthread_setconcurrency - get and set the +level of concurrency +</P> +<H2><A HREF="#toc1" NAME="sect1">Synopsis</A></H2> +<P><B>#include <pthread.h> </B> +</P> +<P><B>int pthread_getconcurrency(void);</B> <BR><B>int +pthread_setconcurrency(int</B> <I>new_level</I><B>); </B> +</P> +<H2><A HREF="#toc2" NAME="sect2">Description</A></H2> +<P>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. +</P> +<P>The <B>pthread_setconcurrency</B> function allows an application +to inform the threads implementation of its desired concurrency +level, <I>new_level</I>. The actual level of concurrency provided by +the implementation as a result of this function call is unspecified. +</P> +<P>If <I>new_level</I> is zero, it causes the implementation to +maintain the concurrency level at its discretion as if +<B>pthread_setconcurrency</B> had never been called. +</P> +<P>The <B>pthread_getconcurrency</B> function shall return the value +set by a previous call to the <B>pthread_setconcurrency</B> function. +If the <B>pthread_setconcurrency</B> function was not previously +called, this function shall return zero to indicate that the +implementation is maintaining the concurrency level. +</P> +<P>A call to <B>pthread_setconcurrency</B> shall inform the +implementation of its desired concurrency level. The implementation +shall use this as a hint, not a requirement. +</P> +<P>If an implementation does not support multiplexing of user threads +on top of several kernel-scheduled entities, the +<B>pthread_setconcurrency</B> and <B>pthread_getconcurrency</B> +functions are provided for source code compatibility but they shall +have no effect when called. To maintain the function semantics, the +<I>new_level</I> parameter is saved when <B>pthread_setconcurrency</B> +is called so that a subsequent call to <B>pthread_getconcurrency</B> +shall return the same value. +</P> +<P><B>Pthreads-w32</B> provides these routines for source code +compatibility only, as described in the previous paragraph.</P> +<H2><A HREF="#toc3" NAME="sect3">Return Value</A></H2> +<P>If successful, the <B>pthread_setconcurrency</B> function shall +return zero; otherwise, an error number shall be returned to indicate +the error. +</P> +<P>The <B>pthread_getconcurrency</B> function shall always return the +concurrency level set by a previous call to <B>pthread_setconcurrency</B> +. If the <B>pthread_setconcurrency</B> function has never been +called, <B>pthread_getconcurrency</B> shall return zero. +</P> +<H2><A HREF="#toc4" NAME="sect4">Errors</A></H2> +<P>The <B>pthread_setconcurrency</B> function shall fail if: +</P> +<DL> + <DT><B>EINVAL</B> + </DT><DD> + The value specified by <I>new_level</I> is negative. + </DD><DT> + <B>EAGAIN</B> + </DT><DD STYLE="margin-bottom: 0.5cm"> + The value specific by <I>new_level</I> would cause a system resource + to be exceeded. + </DD></DL> +<P> +These functions shall not return an error code of [EINTR]. +</P> +<P><I>The following sections are informative.</I> +</P> +<H2><A HREF="#toc5" NAME="sect5">Examples</A></H2> +<P>None. +</P> +<H2><A HREF="#toc6" NAME="sect6">Application Usage</A></H2> +<P>Use of these functions changes the state of the underlying +concurrency upon which the application depends. Library developers +are advised to not use the <B>pthread_getconcurrency</B> and +<B>pthread_setconcurrency</B> functions since their use may conflict +with an applications use of these functions. +</P> +<H2><A HREF="#toc7" NAME="sect7">Rationale</A></H2> +<P>None. +</P> +<H2><A HREF="#toc8" NAME="sect8">Future Directions</A></H2> +<P>None. +</P> +<H2><A HREF="#toc9" NAME="sect9">See Also</A></H2> +<P>The Base Definitions volume of IEEE Std 1003.1-2001, +<I><pthread.h></I> +</P> +<H2><A HREF="#toc10" NAME="sect10">Copyright</A></H2> +<P>Portions of this text are reprinted and reproduced in electronic +form from IEEE Std 1003.1, 2003 Edition, Standard for Information +Technology -- Portable Operating System Interface (POSIX), The Open +Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 <A HREF="http://www.opengroup.org/unix/online.html">http://www.opengroup.org/unix/online.html</A> +. +</P> +<P>Modified by Ross Johnson for use with <A HREF="http://sources.redhat.com/pthreads-win32">Pthreads-w32</A>.</P> +<HR> +<P><A NAME="toc"></A><B>Table of Contents</B></P> +<UL> + <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect0" NAME="toc0">Name</A> + </P> + <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect1" NAME="toc1">Synopsis</A> + </P> + <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect2" NAME="toc2">Description</A> + </P> + <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect3" NAME="toc3">Return + Value</A> + </P> + <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect4" NAME="toc4">Errors</A> + </P> + <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect5" NAME="toc5">Examples</A> + </P> + <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect6" NAME="toc6">Application + Usage</A> + </P> + <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect7" NAME="toc7">Rationale</A> + </P> + <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect8" NAME="toc8">Future + Directions</A> + </P> + <LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect9" NAME="toc9">See + Also</A> + </P> + <LI><P><A HREF="#sect10" NAME="toc10">Copyright</A> + </P> +</UL> +</BODY> +</HTML> |