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ScopeGuard - Kokkos documentation

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ScopeGuard¶

Defined in header <Kokkos_Core.hpp>

Usage¶

Kokkos::ScopeGuard guard(argc, argv);
Kokkos::ScopeGuard guard(Kokkos::InitializationSettings()  // (since 3.7)
                            .set_map_device_id_by("random")
                            .set_num_threads(1));

ScopeGuard is a class to initialize and finalize Kokkos using RAII. It calls Kokkos::initialize with the provided arguments in the constructor and Kokkos::finalize in the destructor. For correct usage, it is mandatory to create a named instance of a ScopeGuard before any calls to Kokkos are issued.

Warning

Change of behavior in version 3.7 (see below). ScopeGuard will abort if either is_initialized() or is_finalized() return true.

Description¶

class ScopeGuard¶

A class calling Kokkos::initialize at the start of its lifetime and Kokkos::finalize at the end of its lifetime.

Constructors

ScopeGuard(int &argc, char *argv[]);¶

Parameters:

argc – number of command line arguments
argv – array of character pointers to null-terminated strings storing the command line arguments

ScopeGuard(InitArguments const &arguments = InitArguments());¶

Parameters:: arguments – struct object with valid initialization arguments

template<class ...Args> ScopeGuard(Args&&... args);¶

Parameters:

args –

arguments to pass to Kokkos::initialize

Possible implementation:

template <class... Args> ScopeGuard(Args&&... args){ initialize(std::forward<Args>(args)...); }

~ScopeGuard();¶

Destructor

Possible implementation:

~ScopeGuard() { finalize(); }

ScopeGuard(ScopeGuard const&) = delete;¶: Copy constructor

ScopeGuard(ScopeGuard&&) = delete;¶: Move constructor

ScopeGuard &operator=(ScopeGuard const&) = delete;¶: Copy assignment operator

ScopeGuard &operator=(ScopeGuard&&) = delete;¶: Move assignment operator

Notes¶

In the constructors, all the parameters are passed to the Kokkos::initialize called internally. See Kokkos::initialize for more details.
Since Kokkos version 3.7, ScopeGuard unconditionally forwards the provided arguments to Kokkos::initialize, which means they have the same preconditions. Until version 3.7, ScopeGuard was calling Kokkos::initialize in its constructor only if Kokkos::is_initialized() was false, and it was calling Kokkos::finalize in its destructor only if it called Kokkos::initialize in its constructor.

We dropped support for the old behavior. If you think you really need it, you may do:
```
auto guard = std::unique_ptr<Kokkos::ScopeGuard>(
    Kokkos::is_initialized() ? new Kokkos::ScopeGuard() : nullptr);
```
or
```
auto guard = Kokkos::is_initialized() ? std::make_optional<Kokkos::ScopeGuard>()
                                    : std::nullopt;
```
with C++17. This will work regardless of the Kokkos version.

Example¶

int main(int argc, char* argv[]) {
    Kokkos::ScopeGuard guard(argc, argv);
    Kokkos::View<double*> my_view("my_view", 10);
    // my_view destructor called before Kokkos::finalize
    // ScopeGuard destructor called, calls Kokkos::finalize
}