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58 lines
3.2 KiB
TeX
58 lines
3.2 KiB
TeX
%begin
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\pagebreak
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\section{\code{target} \code{enter} \code{data} and \code{target} \code{exit} \code{data} Constructs}
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\label{sec:target_enter_exit_data}
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%\section{Simple target enter data and target exit data Constructs}
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\index{constructs!target enter data@\code{target} \code{enter} \code{data}}
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\index{constructs!target exit data@\code{target} \code{exit} \code{data}}
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\index{target enter data construct@\code{target} \code{enter} \code{data} construct}
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\index{target exit data construct@\code{target} \code{exit} \code{data} construct}
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The structured data construct (\code{target}~\code{data}) provides persistent data on a
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device for subsequent \code{target} constructs as shown in the
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\code{target}~\code{data} examples above. This is accomplished by creating a single
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\code{target}~\code{data} region containing \code{target} constructs.
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The unstructured data constructs allow the creation and deletion of data on
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the device at any appropriate point within the host code, as shown below
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with the \code{target}~\code{enter}~\code{data} and \code{target}~\code{exit}~\code{data} constructs.
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\index{map clause@\code{map} clause!alloc map-type@\code{alloc} map-type}
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\index{map clause@\code{map} clause!delete map-type@\code{delete} map-type}
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\index{alloc map-type@\code{alloc} map-type}
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\index{delete map-type@\code{delete} map-type}
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The following C++ code creates/deletes a vector in a constructor/destructor
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of a class. The constructor creates a vector with \code{target}~\code{enter}~\code{data}
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and uses an \code{alloc} modifier in the \code{map} clause to avoid copying values
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to the device. The destructor deletes the data (\code{target}~\code{exit}~\code{data})
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and uses the \code{delete} modifier in the \code{map} clause to avoid copying data
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back to the host. Note, the stand-alone \code{target}~\code{enter}~\code{data} occurs
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after the host vector is created, and the \code{target}~\code{exit}~\code{data}
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construct occurs before the host data is deleted.
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\cppexample[4.5]{target_unstructured_data}{1}
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\pagebreak
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The following C code allocates and frees the data member of a Matrix structure.
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The \code{init\_matrix} function allocates the memory used in the structure and
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uses the \code{target}~\code{enter}~\code{data} directive to map it to the target device. The
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\code{free\_matrix} function removes the mapped array from the target device
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and then frees the memory on the host. Note, the stand-alone
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\code{target}~\code{enter}~\code{data} occurs after the host memory is allocated, and the
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\code{target}~\code{exit}~\code{data} construct occurs before the host data is freed.
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\cexample[4.5]{target_unstructured_data}{1}
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\pagebreak
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The following Fortran code allocates and deallocates a module array. The
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\code{initialize} subroutine allocates the module array and uses the
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\code{target}~\code{enter}~\code{data} directive to map it to the target device. The
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\code{finalize} subroutine removes the mapped array from the target device and
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then deallocates the array on the host. Note, the stand-alone
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\code{target}~\code{enter}~\code{data} occurs after the host memory is allocated, and the
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\code{target}~\code{exit}~\code{data} construct occurs before the host data is deallocated.
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\ffreeexample[4.5]{target_unstructured_data}{1}
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%end
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