Method Do

catboost/libs/data/quantization.cpp:2180–2498

returns nullptr if generateBordersOnly

    public:
        // returns nullptr if generateBordersOnly
        static TQuantizedDataProviderPtr Do(
            const TQuantizationOptions& options,
            TRawDataProviderPtr rawDataProvider,
            TQuantizedFeaturesInfoPtr quantizedFeaturesInfo,
            bool calcQuantizationAndNanModeOnly,
            TRestorableFastRng64* rand,
            NPar::ILocalExecutor* localExecutor,
            const TInitialBorders& initialBorders = Nothing()
        ) {
            auto& srcObjectsCommonData = rawDataProvider->ObjectsData->CommonData;

            auto featuresLayout = InitFeaturesLayoutForQuantizedData(
                *srcObjectsCommonData.FeaturesLayout,
                *quantizedFeaturesInfo->GetFeaturesLayout()
            );

            const bool clearSrcData = rawDataProvider->RefCount() <= 1;
            const bool clearSrcObjectsData = clearSrcData &&
                (rawDataProvider->ObjectsData->RefCount() <= 1);

            /*
             * If these conditions are satisfied quantized features data is only needed for GPU
             *  so it is possible not to store all quantized features bins in CPU RAM
             *  but generate these quantized feature bin values from raw feature values on the fly
             *  just before copying data to GPU memory.
             *  Returned TQuantizedObjectsDataProvider will contain
             *  TExternalFloatValuesHolders and TExternalCatValuesHolders in features data holders.
             */
            const bool storeFeaturesDataAsExternalValuesHolders = false;
            /* Temporarily switch ext columns-off to measure speed
                !clearSrcObjectsData &&
                !featuresLayout->GetTextFeatureCount();*/

            TObjectsGroupingPtr objectsGrouping = rawDataProvider->ObjectsGrouping;

            TSubsetIndexingForBuildBorders subsetIndexingForBuildBorders = GetSubsetForBuildBorders(
                *srcObjectsCommonData.SubsetIndexing,
                *featuresLayout,
                *quantizedFeaturesInfo,
                srcObjectsCommonData.Order,
                options,
                rand,
                localExecutor
            );

            const bool hasDenseSrcData = rawDataProvider->ObjectsData->HasDenseData();

            TMaybe<TQuantizedBuilderData> data;
            TAtomicSharedPtr<TArraySubsetIndexing<ui32>> subsetIndexing;
            TMaybe<TIncrementalDenseIndexing> incrementalIndexing;

            if (!calcQuantizationAndNanModeOnly) {
                data.ConstructInPlace();

                auto flatFeatureCount = featuresLayout->GetExternalFeatureCount();
                data->ObjectsData.PackedBinaryFeaturesData.FlatFeatureIndexToPackedBinaryIndex.resize(
                    flatFeatureCount
                );