\pagebreak
\section{\code{defaultmap} Clause}
\label{sec:defaultmap}

The implicitly-determined, data-mapping and data-sharing attribute
rules of variables referenced in a \code{target} construct can be
changed by the \code{defaultmap} clause introduced in OpenMP 5.0.
The implicit behavior is specified as
\code{alloc}, \code{to}, \code{from}, \code{tofrom},
\code{firstprivate}, \code{none}, \code{default} or \code{present},
and is applied to a variable-category, where
\code{scalar}, \code{aggregate}, \code{allocatable},
and \code{pointer} are the variable categories. 

In OpenMP, a ``category'' has a common data-mapping and data-sharing 
behavior for variable types within the category.
In C/C++, \code{scalar} refers to base-language scalar variables, except pointers.
In Fortran it refers to a scalar variable, as defined by the base language, 
with intrinsic type, and excludes character type.

Also, \code{aggregate} refers to arrays and structures (C/C++) and
derived types (Fortran). Fortran has the additional category of \code{allocatable}.

%In the example below, the first \code{target} construct uses  \code{defaultmap}
%clauses to  explicitly set data-mapping attributes that reproduce 
%the default implicit mapping (data-mapping and data-sharing attributes).  That is, 
%if the \code{defaultmap} clauses were removed, the results would be identical.
In the example below, the first \code{target} construct uses  \code{defaultmap}
clauses to set data-mapping and possibly data-sharing attributes that reproduce 
the default implicit mapping (data-mapping and data-sharing attributes).  That is, 
if the \code{defaultmap} clauses were removed, the results would be identical.

In the second \code{target} construct all implicit behavior is removed
by specifying the \code{none} implicit behavior in the \code{defaultmap} clause.
Hence, all variables must be explicitly mapped.  
In the C/C++ code a scalar (\texttt{s}), an array (\texttt{A}) and a structure 
(\texttt{S}) are explicitly mapped \code{tofrom}.  
The Fortran code uses a derived type (\texttt{D}) in lieu of structure.

The third \code{target} construct shows another usual case for using the \code{defaultmap} clause.
The default mapping for (non-pointer) scalar variables is specified as \code{tofrom}.
Here, the default implicit mapping for \texttt{s3} is \code{tofrom} as specified 
in the \code{defaultmap} clause, and \texttt{s1} and \texttt{s2} are explicitly 
mapped with the \code{firstprivate} data-sharing attribute.

In the fourth \code{target} construct all arrays, structures (C/C++) and derived 
types (Fortran) are mapped with \code{firstprivate} data-sharing behavior by a 
\code{defaultmap} clause with an \code{aggregate} variable category.
For the \texttt{H} allocated array in the Fortran code, the \code{allocable} 
category must be used in a separate \code{defaultmap} clause to acquire 
\code{firsprivate} data-sharing behavior (\texttt{H} has the Fortran allocatable attribute).
% (Common use cases for C/C++ heap storage can be found in \specref{sec:pointer_mapping}.)

\cexample[5.0]{target_defaultmap}{1}

\ffreeexample[5.0]{target_defaultmap}{1}