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ROOT::RDF::RResultPtr< T > Class Template Reference

template<typename T>
class ROOT::RDF::RResultPtr< T >

Smart pointer for the return type of actions.

A wrapper around the result of RDataFrame actions able to trigger calculations lazily.

Template Parameters
TType of the action result

A smart pointer which allows to access the result of a RDataFrame action. The methods of the encapsulated object can be accessed via the arrow operator. Upon invocation of the arrow operator or dereferencing (operator*), the loop on the events and calculations of all scheduled actions are executed if needed. It is possible to iterate on the result proxy if the proxied object is a collection.

for (auto& myItem : myResultProxy) { ... };

If iteration is not supported by the type of the proxied object, a compilation error is thrown.

Definition at line 103 of file RResultPtr.hxx.

Public Types

using Value_t = T
 Convenience alias to simplify access to proxied type.
 

Public Member Functions

 RResultPtr ()=default
 
 RResultPtr (const RResultPtr &)=default
 
template<typename T2 , std::enable_if_t< std::is_constructible< std::shared_ptr< T >, std::shared_ptr< T2 > >::value, int > = 0>
 RResultPtr (const RResultPtr< T2 > &r)
 Convert a RResultPtr<T2> to a RResultPtr<T>.
 
 RResultPtr (RResultPtr &&)=default
 
 ~RResultPtr ()
 
RIterationHelper< T >::Iterator_t begin ()
 Return an iterator to the beginning of the contained object if this makes sense, throw a compilation error otherwise.
 
RIterationHelper< T >::Iterator_t end ()
 Return an iterator to the end of the contained object if this makes sense, throw a compilation error otherwise.
 
T * GetPtr ()
 Get the pointer to the encapsulated object.
 
const T & GetValue ()
 Get a const reference to the encapsulated object.
 
bool IsReady () const
 Check whether the result has already been computed.
 
RResultPtr< T > & OnPartialResult (ULong64_t everyNEvents, std::function< void(T &)> callback)
 Register a callback that RDataFrame will execute "everyNEvents" on a partial result.
 
RResultPtr< T > & OnPartialResultSlot (ULong64_t everyNEvents, std::function< void(unsigned int, T &)> callback)
 Register a callback that RDataFrame will execute in each worker thread concurrently on that thread's partial result.
 
 operator bool () const
 
T & operator* ()
 Get a pointer to the encapsulated object.
 
T * operator-> ()
 Get a pointer to the encapsulated object.
 
RResultPtroperator= (const RResultPtr &)=default
 
RResultPtroperator= (RResultPtr &&)=default
 

Static Public Attributes

static constexpr ULong64_t kOnce = 0ull
 Convenience definition to express a callback must be executed once.
 

Private Types

using SPT_t = std::shared_ptr< T >
 

Private Member Functions

 RResultPtr (std::shared_ptr< T > objPtr, RDFDetail::RLoopManager *lm, std::shared_ptr< RDFInternal::RActionBase > actionPtr)
 
T * Get ()
 Get the pointer to the encapsulated result.
 
void ThrowIfNull ()
 
void TriggerRun ()
 Triggers the event loop in the RLoopManager.
 

Private Attributes

std::shared_ptr< RDFInternal::RActionBasefActionPtr
 Owning pointer to the action that will produce this result.
 
RDFDetail::RLoopManagerfLoopManager = nullptr
 Non-owning pointer to the RLoopManager at the root of this computation graph.
 
SPT_t fObjPtr
 Shared pointer encapsulating the wrapped result.
 

Friends

template<typename T1 >
class RResultPtr
 
template<class T1 , class T2 >
bool operator!= (const RResultPtr< T1 > &lhs, const RResultPtr< T2 > &rhs)
 
template<class T1 >
bool operator!= (const RResultPtr< T1 > &lhs, std::nullptr_t rhs)
 
template<class T1 >
bool operator!= (std::nullptr_t lhs, const RResultPtr< T1 > &rhs)
 
template<class T1 , class T2 >
bool operator== (const RResultPtr< T1 > &lhs, const RResultPtr< T2 > &rhs)
 
template<class T1 >
bool operator== (const RResultPtr< T1 > &lhs, std::nullptr_t rhs)
 
template<class T1 >
bool operator== (std::nullptr_t lhs, const RResultPtr< T1 > &rhs)
 
std::unique_ptr< RDFDetail::RMergeableValue< T > > RDFDetail::GetMergeableValue (RResultPtr< T > &rptr)
 
template<typename T1 >
RResultPtr< T1RDFDetail::MakeResultPtr (const std::shared_ptr< T1 > &, ::ROOT::Detail::RDF::RLoopManager &, std::shared_ptr< RDFInternal::RActionBase >)
 
class ROOT::Internal::RDF::GraphDrawing::GraphCreatorHelper
 
template<typename T1 >
ROOT::RDF::Experimental::RResultMap< T1ROOT::RDF::Experimental::VariationsFor (RResultPtr< T1 > resPtr)
 
class RResultHandle
 

#include <ROOT/RResultPtr.hxx>

Member Typedef Documentation

◆ SPT_t

template<typename T >
using ROOT::RDF::RResultPtr< T >::SPT_t = std::shared_ptr<T>
private

Definition at line 105 of file RResultPtr.hxx.

◆ Value_t

template<typename T >
using ROOT::RDF::RResultPtr< T >::Value_t = T

Convenience alias to simplify access to proxied type.

Definition at line 186 of file RResultPtr.hxx.

Constructor & Destructor Documentation

◆ RResultPtr() [1/5]

template<typename T >
ROOT::RDF::RResultPtr< T >::RResultPtr ( std::shared_ptr< T >  objPtr,
RDFDetail::RLoopManager lm,
std::shared_ptr< RDFInternal::RActionBase actionPtr 
)
inlineprivate

Definition at line 179 of file RResultPtr.hxx.

◆ RResultPtr() [2/5]

template<typename T >
ROOT::RDF::RResultPtr< T >::RResultPtr ( )
default

◆ RResultPtr() [3/5]

template<typename T >
ROOT::RDF::RResultPtr< T >::RResultPtr ( const RResultPtr< T > &  )
default

◆ RResultPtr() [4/5]

template<typename T >
ROOT::RDF::RResultPtr< T >::RResultPtr ( RResultPtr< T > &&  )
default

◆ ~RResultPtr()

template<typename T >
ROOT::RDF::RResultPtr< T >::~RResultPtr ( )
inline

Definition at line 195 of file RResultPtr.hxx.

◆ RResultPtr() [5/5]

template<typename T >
template<typename T2 , std::enable_if_t< std::is_constructible< std::shared_ptr< T >, std::shared_ptr< T2 > >::value, int > = 0>
ROOT::RDF::RResultPtr< T >::RResultPtr ( const RResultPtr< T2 > &  r)
inline

Convert a RResultPtr<T2> to a RResultPtr<T>.

Useful e.g. to store a number of RResultPtr<TH1D> and RResultPtr<TH2D> in a std::vector<RResultPtr<TH1>>. The requirements on T2 and T are the same as for conversion between std::shared_ptr<T2> and std::shared_ptr<T>.

Definition at line 208 of file RResultPtr.hxx.

Member Function Documentation

◆ begin()

template<typename T >
RIterationHelper< T >::Iterator_t ROOT::RDF::RResultPtr< T >::begin ( )
inline

Return an iterator to the beginning of the contained object if this makes sense, throw a compilation error otherwise.

Definition at line 243 of file RResultPtr.hxx.

◆ end()

template<typename T >
RIterationHelper< T >::Iterator_t ROOT::RDF::RResultPtr< T >::end ( )
inline

Return an iterator to the end of the contained object if this makes sense, throw a compilation error otherwise.

Definition at line 253 of file RResultPtr.hxx.

◆ Get()

template<typename T >
T * ROOT::RDF::RResultPtr< T >::Get ( )
inlineprivate

Get the pointer to the encapsulated result.

Ownership is not transferred to the caller. Triggers event loop and execution of all actions booked in the associated RLoopManager.

Definition at line 166 of file RResultPtr.hxx.

◆ GetPtr()

template<typename T >
T * ROOT::RDF::RResultPtr< T >::GetPtr ( )
inline

Get the pointer to the encapsulated object.

Triggers event loop and execution of all actions booked in the associated RLoopManager.

Definition at line 222 of file RResultPtr.hxx.

◆ GetValue()

template<typename T >
const T & ROOT::RDF::RResultPtr< T >::GetValue ( )
inline

Get a const reference to the encapsulated object.

Triggers event loop and execution of all actions booked in the associated RLoopManager.

Definition at line 214 of file RResultPtr.hxx.

◆ IsReady()

template<typename T >
bool ROOT::RDF::RResultPtr< T >::IsReady ( ) const
inline

Check whether the result has already been computed.

auto res = df.Count();
res.IsReady(); // false, access will trigger event loop
std::cout << *res << std::endl; // triggers event loop
res.IsReady(); // true

Definition at line 372 of file RResultPtr.hxx.

◆ OnPartialResult()

template<typename T >
RResultPtr< T > & ROOT::RDF::RResultPtr< T >::OnPartialResult ( ULong64_t  everyNEvents,
std::function< void(T &)>  callback 
)
inline

Register a callback that RDataFrame will execute "everyNEvents" on a partial result.

Parameters
[in]everyNEventsFrequency at which the callback will be called, as a number of events processed
[in]callbacka callable with signature void(Value_t&) where Value_t is the type of the value contained in this RResultPtr
Returns
this RResultPtr, to allow chaining of OnPartialResultSlot with other calls

The callback must be a callable (lambda, function, functor class...) that takes a reference to the result type as argument and returns nothing. RDataFrame will invoke registered callbacks passing partial action results as arguments to them (e.g. a histogram filled with a part of the selected events, a counter incremented only up to a certain point, a mean over a subset of the events and so forth).

Callbacks can be used e.g. to inspect partial results of the analysis while the event loop is running. For example one can draw an up-to-date version of a result histogram every 100 entries like this:

auto h = tdf.Histo1D("x");
TCanvas c("c","x hist");
h.OnPartialResult(100, [&c](TH1D &h_) { c.cd(); h_.Draw(); c.Update(); });
h->Draw(); // event loop runs here, this `Draw` is executed after the event loop is finished
#define c(i)
Definition RSha256.hxx:101
#define h(i)
Definition RSha256.hxx:106
The Canvas class.
Definition TCanvas.h:23
1-D histogram with a double per channel (see TH1 documentation)}
Definition TH1.h:618
virtual void Draw(Option_t *option="")
Draw this histogram with options.
Definition TH1.cxx:3074

A value of 0 for everyNEvents indicates the callback must be executed only once, before running the event loop. A conveniece definition kOnce is provided to make this fact more expressive in user code (see snippet below). Multiple callbacks can be registered with the same RResultPtr (i.e. results of RDataFrame actions) and will be executed sequentially. Callbacks are executed in the order they were registered. The type of the value contained in a RResultPtr is also available as RResultPtr<T>::Value_t, e.g.

auto h = tdf.Histo1D("x");
// h.kOnce is 0
// decltype(h)::Value_t is TH1D

When implicit multi-threading is enabled, the callback:

  • will never be executed by multiple threads concurrently: it needs not be thread-safe. For example the snippet above that draws the partial histogram on a canvas works seamlessly in multi-thread event loops.
  • will always be executed "everyNEvents": partial results will "contain" that number of events more from one call to the next
  • might be executed by a different worker thread at different times: the value of std::this_thread::get_id() might change between calls

To register a callback that is called by each worker thread (concurrently) every N events one can use OnPartialResultSlot().

Definition at line 304 of file RResultPtr.hxx.

◆ OnPartialResultSlot()

template<typename T >
RResultPtr< T > & ROOT::RDF::RResultPtr< T >::OnPartialResultSlot ( ULong64_t  everyNEvents,
std::function< void(unsigned int, T &)>  callback 
)
inline

Register a callback that RDataFrame will execute in each worker thread concurrently on that thread's partial result.

Parameters
[in]everyNEventsFrequency at which the callback will be called by each thread, as a number of events processed
[in]callbackA callable with signature void(unsigned int, Value_t&) where Value_t is the type of the value contained in this RResultPtr
Returns
this RResultPtr, to allow chaining of OnPartialResultSlot with other calls

See OnPartialResult for a generic explanation of the callback mechanism. Compared to OnPartialResult, this method has two major differences:

  • all worker threads invoke the callback once every specified number of events. The event count is per-thread, and callback invocation might happen concurrently (i.e. the callback must be thread-safe)
  • the callable must take an extra unsigned int parameter corresponding to a multi-thread "processing slot": this is a "helper value" to simplify writing thread-safe callbacks: different worker threads might invoke the callback concurrently but always with different slot numbers.
  • a value of 0 for everyNEvents indicates the callback must be executed once per slot.

For example, the following snippet prints out a thread-safe progress bar of the events processed by RDataFrame

auto c = tdf.Count(); // any action would do, but `Count` is the most lightweight
std::string progress;
std::mutex bar_mutex;
c.OnPartialResultSlot(nEvents / 100, [&progress, &bar_mutex](unsigned int, ULong64_t &) {
std::lock_guard<std::mutex> lg(bar_mutex);
progress.push_back('#');
std::cout << "\r[" << std::left << std::setw(100) << progress << ']' << std::flush;
});
std::cout << "Analysis running..." << std::endl;
*c; // trigger the event loop by accessing an action's result
std::cout << "\nDone!" << std::endl;
unsigned long long ULong64_t
Definition RtypesCore.h:81

Definition at line 350 of file RResultPtr.hxx.

◆ operator bool()

template<typename T >
ROOT::RDF::RResultPtr< T >::operator bool ( ) const
inlineexplicit

Definition at line 194 of file RResultPtr.hxx.

◆ operator*()

template<typename T >
T & ROOT::RDF::RResultPtr< T >::operator* ( )
inline

Get a pointer to the encapsulated object.

Triggers event loop and execution of all actions booked in the associated RLoopManager.

Definition at line 226 of file RResultPtr.hxx.

◆ operator->()

template<typename T >
T * ROOT::RDF::RResultPtr< T >::operator-> ( )
inline

Get a pointer to the encapsulated object.

Ownership is not transferred to the caller. Triggers event loop and execution of all actions booked in the associated RLoopManager.

Definition at line 235 of file RResultPtr.hxx.

◆ operator=() [1/2]

template<typename T >
RResultPtr & ROOT::RDF::RResultPtr< T >::operator= ( const RResultPtr< T > &  )
default

◆ operator=() [2/2]

template<typename T >
RResultPtr & ROOT::RDF::RResultPtr< T >::operator= ( RResultPtr< T > &&  )
default

◆ ThrowIfNull()

template<typename T >
void ROOT::RDF::RResultPtr< T >::ThrowIfNull ( )
inlineprivate

Definition at line 173 of file RResultPtr.hxx.

◆ TriggerRun()

template<typename T >
void ROOT::RDF::RResultPtr< T >::TriggerRun
private

Triggers the event loop in the RLoopManager.

Definition at line 381 of file RResultPtr.hxx.

Friends And Related Symbol Documentation

◆ RResultPtr

template<typename T >
template<typename T1 >
friend class RResultPtr
friend

Definition at line 109 of file RResultPtr.hxx.

◆ operator!= [1/3]

template<typename T >
template<class T1 , class T2 >
bool operator!= ( const RResultPtr< T1 > &  lhs,
const RResultPtr< T2 > &  rhs 
)
friend

Definition at line 393 of file RResultPtr.hxx.

◆ operator!= [2/3]

template<typename T >
template<class T1 >
bool operator!= ( const RResultPtr< T1 > &  lhs,
std::nullptr_t  rhs 
)
friend

Definition at line 411 of file RResultPtr.hxx.

◆ operator!= [3/3]

template<typename T >
template<class T1 >
bool operator!= ( std::nullptr_t  lhs,
const RResultPtr< T1 > &  rhs 
)
friend

Definition at line 417 of file RResultPtr.hxx.

◆ operator== [1/3]

template<typename T >
template<class T1 , class T2 >
bool operator== ( const RResultPtr< T1 > &  lhs,
const RResultPtr< T2 > &  rhs 
)
friend

Definition at line 387 of file RResultPtr.hxx.

◆ operator== [2/3]

template<typename T >
template<class T1 >
bool operator== ( const RResultPtr< T1 > &  lhs,
std::nullptr_t  rhs 
)
friend

Definition at line 399 of file RResultPtr.hxx.

◆ operator== [3/3]

template<typename T >
template<class T1 >
bool operator== ( std::nullptr_t  lhs,
const RResultPtr< T1 > &  rhs 
)
friend

Definition at line 405 of file RResultPtr.hxx.

◆ RDFDetail::GetMergeableValue

template<typename T >
std::unique_ptr< RDFDetail::RMergeableValue< T > > RDFDetail::GetMergeableValue ( RResultPtr< T > &  rptr)
friend

◆ RDFDetail::MakeResultPtr

template<typename T >
template<typename T1 >
RResultPtr< T1 > RDFDetail::MakeResultPtr ( const std::shared_ptr< T1 > &  ,
::ROOT::Detail::RDF::RLoopManager ,
std::shared_ptr< RDFInternal::RActionBase  
)
friend

◆ ROOT::Internal::RDF::GraphDrawing::GraphCreatorHelper

template<typename T >
friend class ROOT::Internal::RDF::GraphDrawing::GraphCreatorHelper
friend

Definition at line 132 of file RResultPtr.hxx.

◆ ROOT::RDF::Experimental::VariationsFor

template<typename T >
template<typename T1 >
ROOT::RDF::Experimental::RResultMap< T1 > ROOT::RDF::Experimental::VariationsFor ( RResultPtr< T1 resPtr)
friend

◆ RResultHandle

template<typename T >
friend class RResultHandle
friend

Definition at line 134 of file RResultPtr.hxx.

Member Data Documentation

◆ fActionPtr

template<typename T >
std::shared_ptr<RDFInternal::RActionBase> ROOT::RDF::RResultPtr< T >::fActionPtr
private

Owning pointer to the action that will produce this result.

Ownership is shared with other copies of this ResultPtr.

Definition at line 158 of file RResultPtr.hxx.

◆ fLoopManager

template<typename T >
RDFDetail::RLoopManager* ROOT::RDF::RResultPtr< T >::fLoopManager = nullptr
private

Non-owning pointer to the RLoopManager at the root of this computation graph.

The RLoopManager is guaranteed to be always in scope if fLoopManager is not a nullptr.

Definition at line 154 of file RResultPtr.hxx.

◆ fObjPtr

template<typename T >
SPT_t ROOT::RDF::RResultPtr< T >::fObjPtr
private

Shared pointer encapsulating the wrapped result.

Definition at line 155 of file RResultPtr.hxx.

◆ kOnce

template<typename T >
constexpr ULong64_t ROOT::RDF::RResultPtr< T >::kOnce = 0ull
staticconstexpr

Convenience definition to express a callback must be executed once.

Definition at line 187 of file RResultPtr.hxx.

  • tree/dataframe/inc/ROOT/RDF/InterfaceUtils.hxx
  • tree/dataframe/inc/ROOT/RResultPtr.hxx