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gmx::ObservablesReducerBuilder Class Reference

#include <gromacs/mdtypes/observablesreducer.h>


Builder for ObservablesReducer.

Receives subscriptions from MD modules. Caller should call build() once all subscriptions have been received, and then not attempt any further subscriptions or builds. At that time, the builder may be destructed.

This builder will

Note that the builder callbacks do not follow the approach of MDModulesNotifier because that requires that the same value is passed to all recipients. Here a distinct value goes to each recipient, ie. a different view of the communication buffer.

In order to avoid circular build-time dependencies between the ObservablesReducer (and its builder) with the modules that use it, the latter can directly call methods on the former, supplying anonymous callbacks to be used by the former to contact the latter. CallbackAfterReduction and CallbackFromBuilder are of this type.

A callback type CallBackToRequireReduction is also used instead of a direct method call on ObservablesReducer to require reduction. This is implemented by calling a method on the Impl object of a ObservablesReducer. This extends the interface of ObservablesReducer in a way that is not directly visible. That complexity provides two benefits:

It is the subscribers' responsibility to coordinate so that all subscribers on all ranks agree on the need to communicate, e.g. by orchestrating communication based on the current step number or a previous message.


class  Impl
 Impl class for ObservablesReducerBuilder. More...

Public Types

using CallbackAfterReduction = std::function< void(Step)>
 Convenience type for the callback subscribers to provide when they require reduction.
using CallbackToRequireReduction = std::function< ObservablesReducerStatus(ReductionRequirement)>
 Convenience type for the callback subscribers call to require reduction. More...
using CallbackFromBuilder = std::function< void(CallbackToRequireReduction &&, ArrayRef< double >)>
 Convenience type for the callback from the builder to notify the subscribers of the callback they will own and later use to require reduction and the view of the communication buffer they will later use.

Public Member Functions

 ObservablesReducerBuilder ()
 ~ObservablesReducerBuilder ()
 ObservablesReducerBuilder (ObservablesReducerBuilder &&other) noexcept
 Move constructor.
ObservablesReducerBuilderoperator= (ObservablesReducerBuilder &&other) noexcept
 Move assignment operator.
void addSubscriber (int sizeRequired, CallbackFromBuilder &&callbackFromBuilder, CallbackAfterReduction &&callbackAfterReduction)
 Add a subscriber to the ObservablesReducer that will later be built in build() More...
ObservablesReducer build ()
 Build a ObservablesReducer to which any subscribers have been added. More...

Member Typedef Documentation

Convenience type for the callback subscribers call to require reduction.

When called, the status it returns can be used for checking the internal expectations of the subscriber on whether reduction has already occurred this step, or not.

Member Function Documentation

void gmx::ObservablesReducerBuilder::addSubscriber ( int  sizeRequired,
CallbackFromBuilder &&  callbackFromBuilder,
CallbackAfterReduction &&  callbackAfterReduction 

Add a subscriber to the ObservablesReducer that will later be built in build()

Takes ownership of both callbacks supplied by the subscribing module. This approach ensures that time is not spent in the MD loop constructing std::function objects, because constructing one of those requires 1-2 heap allocations (depending on the size of the lambda capture).

Must not be called after build()

ObservablesReducer gmx::ObservablesReducerBuilder::build ( )

Build a ObservablesReducer to which any subscribers have been added.

Must be called only once. Notifies each subscriber (via the CallbackFromBuilder that it supplied) of the view of the reduction buffer that they will use and the CallbackToRequireReduction that they will use.

The documentation for this class was generated from the following files: