Function ParallelStripeView

catboost/cuda/cuda_lib/cuda_buffer.h:530–567

    template <class T, EPtrType Type>
    inline TCudaBuffer<T, TStripeMapping, Type> ParallelStripeView(const TCudaBuffer<T, TStripeMapping, Type>& buffer,
                                                                   const TSlice& slice,
                                                                   ui32 column = 0) {
        const TStripeMapping& srcMapping = buffer.GetMapping();
        TCudaBuffer<T, TStripeMapping, Type> parallelViewBuffer;
        const ui32 devCount = NCudaLib::GetCudaManager().GetDeviceCount();

        TVector<TSlice> srcSlices(devCount);
        TVector<TSlice> viewSlices(devCount);

        {
            TSlice firstDevSlice = srcMapping.DeviceSlice(0);
            CB_ENSURE(slice.Size() <= firstDevSlice.Size(), slice << " / " << firstDevSlice);

            ui32 cursor = 0;
            for (ui32 dev = 0; dev < devCount; ++dev) {
                srcSlices[dev] = TSlice(slice.Left + firstDevSlice.Size() * dev, slice.Right + firstDevSlice.Size() * dev);
                viewSlices[dev] = TSlice(cursor, cursor + slice.Size());
                cursor += slice.Size();
                CB_ENSURE(srcMapping.DeviceSlice(dev).Size() == firstDevSlice.Size());
            }

            parallelViewBuffer.Mapping = NCudaLib::TStripeMapping(std::move(viewSlices),
                                                                  srcMapping.SingleObjectSize());
        }

        for (ui32 dev : parallelViewBuffer.Mapping.NonEmptyDevices()) {
            const ui64 columnsShift = NAligment::ColumnShift(srcMapping.MemoryUsageAt(dev), column);

            const auto devSlice = srcSlices[dev];
            if (buffer.Buffers[dev].NotEmpty()) {
                parallelViewBuffer.Buffers[dev] = buffer.Buffers[dev].ShiftedBuffer(columnsShift + srcMapping.DeviceMemoryOffset(dev, devSlice));
            }
        }
        parallelViewBuffer.IsSliceView = true;

        return parallelViewBuffer;
    }

    template <class T>
    class TParallelStripeVectorBuilder {