Function QuantizeNonDefaultValues

catboost/libs/data/quantization.cpp:938–980

    // TCallback accepts (dstIndex, quantizedValue) arguments
    template <class TSrc, class TCallback>
    static void QuantizeNonDefaultValues(
        const TSrc& srcFeature,
        const TIncrementalDenseIndexing& incrementalDenseIndexing,
        TValueQuantizer<TSrc> valueQuantizer,
        NPar::ILocalExecutor* localExecutor,
        TCallback&& callback
    ) {
        using TValueType = typename TSrc::TValueType;
        using TDenseSrcData = TPolymorphicArrayValuesHolder<TSrc>;
        using TSparseSrcData = TSparsePolymorphicArrayValuesHolder<TSrc>;

        if (const auto* denseSrcFeature = dynamic_cast<const TDenseSrcData*>(&srcFeature)){
            if (std::get_if<TIndexedSubset<ui32>>(&incrementalDenseIndexing.SrcSubsetIndexing)) {
                TConstArrayRef<ui32> dstIndices
                    = std::get<TIndexedSubset<ui32>>(incrementalDenseIndexing.DstIndexing);

                denseSrcFeature->GetData()->CloneWithNewSubsetIndexing(
                    &incrementalDenseIndexing.SrcSubsetIndexing
                )->ParallelForEach(
                    [=] (ui32 i, TValueType srcValue) {
                        callback(dstIndices[i], valueQuantizer.Quantize(srcValue));
                    },
                    localExecutor
                );
            } else {
                denseSrcFeature->GetData()->ParallelForEach(
                    [=] (ui32 dstIdx, TValueType srcValue) {
                        callback(dstIdx, valueQuantizer.Quantize(srcValue));
                    },
                    localExecutor
                );
            }
        } else if (const auto* sparseSrcFeature = dynamic_cast<const TSparseSrcData*>(&srcFeature)) {
            const auto& sparseArray = sparseSrcFeature->GetData();
            sparseArray.ForEachNonDefault(
                [=] (ui32 dstIdx, TValueType srcValue) {
                    callback(dstIdx, valueQuantizer.Quantize(srcValue));
                }
            );
        } else {
            CB_ENSURE_INTERNAL(false, "QuantizeNonDefaultValues: unsupported src feature type");
        }
    }

    template <
        class TStoredDstValue,