Function MakeDataProvider

catboost/libs/data/data_provider.h:224–286

     */
    template <class TTObjectsDataProvider>
    TIntrusivePtr<TDataProviderTemplate<TTObjectsDataProvider>> MakeDataProvider(
        TMaybe<TObjectsGroupingPtr> objectsGrouping, // if undefined ObjectsGrouping created from data
        TBuilderData<typename TTObjectsDataProvider::TData>&& builderData,
        bool skipCheck,
        bool forceUnitAutoPairWeights,
        NPar::ILocalExecutor* localExecutor
    ) {
        if (!skipCheck) {
            /* most likely have been already checked, but call it here for consistency with
             * overall checking logic
             */
            builderData.MetaInfo.Validate();
        }

        TIntrusivePtr<TTObjectsDataProvider> objectsData;

        auto makeObjectsDataProvider = [&] () {
            objectsData = MakeIntrusive<TTObjectsDataProvider>(
                objectsGrouping,
                std::move(builderData.CommonObjectsData),
                std::move(builderData.ObjectsData),
                skipCheck,
                localExecutor
            );
        };

        TVector<std::function<void()>> tasks;

        /* if objectsGrouping is defined we can run objectsData and target data creation in parallel
         * otherwise create grouping in objectsDataProvider first and then pass it to target constructor
         */
        if (objectsGrouping) {
            tasks.emplace_back(makeObjectsDataProvider);
        } else {
            makeObjectsDataProvider();
            objectsGrouping = objectsData->GetObjectsGrouping();
        }

        // TMaybe - to defer initialization to async task
        TMaybe<TRawTargetDataProvider> rawTargetData;

        tasks.emplace_back(
            [&] () {
                rawTargetData = MakeMaybe<TRawTargetDataProvider>(
                    *objectsGrouping,
                    std::move(builderData.TargetData),
                    skipCheck,
                    forceUnitAutoPairWeights,
                    localExecutor
                );
            }
        );

        ExecuteTasksInParallel(&tasks, localExecutor);


        return MakeIntrusive<TDataProviderTemplate<TTObjectsDataProvider>>(
            std::move(builderData.MetaInfo), // assuming copying it is not very expensive