mirror of
https://github.com/OpenMP/Examples.git
synced 2025-04-04 05:41:33 +01:00
58 lines
2.4 KiB
TeX
58 lines
2.4 KiB
TeX
%\pagebreak
|
|
\section{\kcode{copyprivate} Clause}
|
|
\label{sec:copyprivate}
|
|
\index{clauses!copyprivate@\kcode{copyprivate}}
|
|
\index{copyprivate clause@\kcode{copyprivate} clause}
|
|
|
|
The \kcode{copyprivate} clause can be used to broadcast values acquired by a single
|
|
thread directly to all instances of the private variables in the other threads.
|
|
In this example, if the routine is called from the sequential part, its behavior
|
|
is not affected by the presence of the directives. If it is called from a \kcode{parallel}
|
|
region, then the actual arguments with which \ucode{a} and \ucode{b} are associated
|
|
must be private.
|
|
|
|
\index{constructs!single@\kcode{single}}
|
|
\index{single construct@\kcode{single} construct}
|
|
The thread that executes the structured block associated with the \kcode{single}
|
|
construct broadcasts the values of the private variables \ucode{a}, \ucode{b},
|
|
\ucode{x}, and
|
|
\ucode{y} from its implicit task's data environment to the data environments
|
|
of the other implicit tasks in the thread team. The broadcast completes before
|
|
any of the threads have left the barrier at the end of the construct.
|
|
|
|
\cexample{copyprivate}{1}
|
|
|
|
\fexample{copyprivate}{1}
|
|
|
|
\index{constructs!masked@\kcode{masked}}
|
|
\index{masked construct@\kcode{masked} construct}
|
|
In this example, assume that the input must be performed by the primary thread.
|
|
Since the \kcode{masked} construct does not support the \kcode{copyprivate} clause,
|
|
it cannot broadcast the input value that is read. However, \kcode{copyprivate}
|
|
is used to broadcast an address where the input value is stored.
|
|
|
|
\cexample[5.1]{copyprivate}{2}
|
|
|
|
\fexample[5.1]{copyprivate}{2}
|
|
|
|
Suppose that the number of lock variables required within a \kcode{parallel} region
|
|
cannot easily be determined prior to entering it. The \kcode{copyprivate} clause
|
|
can be used to provide access to shared lock variables that are allocated within
|
|
that \kcode{parallel} region.
|
|
|
|
\cexample{copyprivate}{3}
|
|
|
|
\begin{fortranspecific}
|
|
\fnexample{copyprivate}{3}
|
|
|
|
Note that the effect of the \kcode{copyprivate} clause on a variable with the
|
|
\bcode{allocatable} attribute is different than on a variable with the \bcode{pointer}
|
|
attribute. The value of \ucode{A} is copied (as if by intrinsic assignment) and
|
|
the pointer \ucode{B} is copied (as if by pointer assignment) to the corresponding
|
|
list items in the other implicit tasks belonging to the \kcode{parallel} region.
|
|
|
|
\fnexample{copyprivate}{4}
|
|
\end{fortranspecific}
|
|
|
|
|