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https://issues.apache.org/jira/browse/ARROW-2447?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16788770#comment-16788770
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Pearu Peterson commented on ARROW-2447:
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FYI, CUDA introduces
[MemoryType|https://docs.nvidia.com/cuda/cuda-runtime-api/group__CUDART__TYPES.html#group__CUDART__TYPES_1g13de56a8fe75569530ecc3a3106e9b6d]
concept that together with
[cudaPointerGetAttributes|https://docs.nvidia.com/cuda/cuda-runtime-api/group__CUDART__UNIFIED.html#group__CUDART__UNIFIED_1gd89830e17d399c064a2f3c3fa8bb4390]
allows to determine if the given pointer value can be accessed from device or
host or from both, and when on device then what is the device number.
> [C++] Create a device abstraction
> ---------------------------------
>
> Key: ARROW-2447
> URL: https://issues.apache.org/jira/browse/ARROW-2447
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++, GPU
> Affects Versions: 0.9.0
> Reporter: Antoine Pitrou
> Assignee: Pearu Peterson
> Priority: Major
> Fix For: 0.14.0
>
>
> Right now, a plain Buffer doesn't carry information about where it actually
> lies. That information also cannot be passed around, so you get APIs like
> {{PlasmaClient}} which take or return device number integers, and have
> implementations which hardcode operations on CUDA buffers. Also, unsuspecting
> receivers of a {{Buffer}} pointer may try to act on the underlying memory
> without knowing whether it's CPU-reachable or not.
> Here is a sketch for a proposed Device abstraction:
> {code}
> class Device {
> enum DeviceKind { KIND_CPU, KIND_CUDA };
> virtual DeviceKind kind() const;
> //MemoryPool* default_memory_pool() const;
> //std::shared_ptr<Buffer> Allocate(...);
> };
> class CpuDevice : public Device {};
> class CudaDevice : public Device {
> int device_num() const;
> };
> class Buffer {
> virtual DeviceKind device_kind() const;
> virtual std::shared_ptr<Device> device() const;
> virtual bool on_cpu() const {
> return true;
> }
> const uint8_t* cpu_data() const {
> return on_cpu() ? data() : nullptr;
> }
> uint8_t* cpu_mutable_data() {
> return on_cpu() ? mutable_data() : nullptr;
> }
> virtual CopyToCpu(std::shared_ptr<Buffer> dest) const;
> virtual CopyFromCpu(std::shared_ptr<Buffer> src);
> };
> class CudaBuffer : public Buffer {
> virtual bool on_cpu() const {
> return false;
> }
> };
> CopyBuffer(std::shared_ptr<Buffer> dest, const std::shared_ptr<Buffer> src);
> {code}
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