Function MapGetApprox

catboost/private/libs/distributed/master.cpp:906–959

void MapGetApprox(
    const NCB::TTrainingDataProviders& data,
    const TLearnContext& ctx,
    bool useBestModel,
    TVector<TVector<double>>* learnApprox,  // [dim][docIdx], can be nullptr
    TVector<TVector<TVector<double>>>* testApprox) { // [test][dim][docIdx], can be nullptr

    Y_ASSERT(ctx.Params.SystemOptions->IsMaster());

    const TVector<TApproxesResult> resultsFromWorkers = ApplyMapper<TApproxGetter>(
        TMasterEnvironment::GetRef().RootEnvironment->GetSlaveCount(),
        TMasterEnvironment::GetRef().SharedTrainData,
        TApproxGetterParams{
            learnApprox != nullptr,
            testApprox != nullptr,
            /*ReturnBestTestApprox*/ useBestModel
        }
    );

    auto approxDimension = ctx.LearnProgress->ApproxDimension;

    if (learnApprox) {
        MergeApproxesFromWorkers(
            resultsFromWorkers,
            approxDimension,
            data.Learn->GetObjectCount(),
            /*getApproxPart*/ [&] (const TApproxesResult& resultFromWorker) -> const TVector<TVector<double>>& {
                return resultFromWorker.LearnApprox;
            },
            learnApprox
        );
    }

    if (testApprox) {
        auto testCount = data.Test.size();

        testApprox->resize(testCount);
        for (auto testIdx : xrange(testCount)) {
            const bool assignFromBestApprox = useBestModel && (testIdx == 0);

            MergeApproxesFromWorkers(
                resultsFromWorkers,
                approxDimension,
                data.Test[testIdx]->GetObjectCount(),
                /*getApproxPart*/ [&] (const TApproxesResult& resultFromWorker) -> const TVector<TVector<double>>& {
                    return assignFromBestApprox ?
                        resultFromWorker.BestTestApprox :
                        resultFromWorker.TestApprox[testIdx];
                },
                &(*testApprox)[testIdx]
            );
        }
    }
}