mirror of
https://github.com/OpenMP/Examples.git
synced 2025-04-16 19:20:50 +01:00
47 lines
2.2 KiB
TeX
47 lines
2.2 KiB
TeX
\section{Array Shaping}
|
|
\label{sec:array-shaping}
|
|
\index{array shaping!in motion-clause@in \plc{motion-clause}}
|
|
\index{constructs!target update@\code{target}~\code{update}}
|
|
\index{target update construct@\code{target}~\code{update} construct!to clause@\code{to} clause}
|
|
\index{target update construct@\code{target}~\code{update} construct!from clause@\code{from} clause}
|
|
|
|
\index{directives!declare target@\code{declare}~\code{target}}
|
|
\index{declare target directive@\code{declare}~\code{target} directive}
|
|
|
|
\index{directives!begin declare target@\code{begin}~\code{declare}~\code{target}}
|
|
\index{begin declare target directive@\code{begin}~\code{declare}~\code{target} directive}
|
|
|
|
\ccppspecificstart
|
|
A pointer variable can be shaped to a multi-dimensional array to facilitate
|
|
data access. This is achieved by a \plc{shape-operator} casted in front of
|
|
a pointer (lvalue expression):
|
|
\begin{description}
|
|
\item[]\hspace*{5mm}\code{([$s_1$][$s_2$]...[$s_n$])}\plc{pointer}
|
|
\end{description}
|
|
where each $s_i$ is an integral-type expression of positive value.
|
|
The shape-operator can appear in either the \plc{motion-clause}
|
|
of the \code{target}~\code{update} directive or the \code{depend} clause.
|
|
|
|
The following example shows the use of the shape-operator in the
|
|
\code{target}~\code{update} directive. The shape-operator \code{([nx][ny+2])}
|
|
casts pointer variable $a$ to a 2-dimensional array of size
|
|
\plc{nx}$\times$\plc{(ny+2)}. The resulting array is then accessed as
|
|
array sections (such as \code{[0:nx][1]} and \code{[0:nx][ny]})
|
|
in the \code{from} or \code{to} clause for transferring two columns of
|
|
noncontiguous boundary data from or to the device.
|
|
Note the use of additional parentheses
|
|
around the shape-operator and $a$ to ensure the correct precedence
|
|
over array-section operations.
|
|
|
|
\cnexample[5.1]{array_shaping}{1}
|
|
\ccppspecificend
|
|
\clearpage
|
|
|
|
The shape operator is not defined for Fortran. Explicit array shaping
|
|
of procedure arguments can be used instead to achieve a similar goal.
|
|
Below is the Fortran-equivalent of the above example that illustrates
|
|
the support of transferring two rows of noncontiguous boundary
|
|
data in the \code{target}~\code{update} directive.
|
|
|
|
\ffreeexample[5.2]{array_shaping}{1}
|