What is hipCUB?#
hipCUB is a thin header-only wrapper library on top of rocPRIM or CUB. It enables developers to port project using CUB library to the HIP layer and to run them on AMD hardware. In the ROCm environment, hipCUB uses rocPRIM library as the backend, while on CUDA platforms it uses CUB.
Here are some key points to be noted:
When using hipCUB, include only
<hipcub/hipcub.hpp>
header.When rocPRIM is used as backend,
HIPCUB_ROCPRIM_API
is defined.When CUB is used as backend,
HIPCUB_CUB_API
is defined.Backends are automatically selected based on the platform detected by HIP layer (
__HIP_PLATFORM_AMD__
,__HIP_PLATFORM_NVIDIA__
).
rocPRIM backend#
hipCUB with the rocPRIM backend may not support all the CUB functions and features because of the differences between the ROCm (HIP) platform and the CUDA platform.
Unsupported features and differences:
Functions, classes, and macros that are not in the public API or undocumented are not supported.
Device-wide primitives can’t be called from kernels (dynamic parallelism is not supported in HIP on ROCm).
DeviceSpmv
is not supported.Fancy iterators:
CacheModifiedInputIterator
,CacheModifiedOutputIterator
, andTexRefInputIterator
are not supported.Thread I/O:
CacheLoadModifier
,CacheStoreModifier
cache modifiers are not supported.ThreadLoad
,ThreadStore
functions are not supported.
Storage management and debug functions:
Debug
,PtxVersion
,SmVersion
functions andCubDebug
,CubDebugExit
,_CubLog
macros are not supported.
Intrinsics:
ThreadExit
,ThreadTrap
are not supported.Warp thread masks (when used) are 64-bit unsigned integers.
member_mask
input argument is ignored inWARP_*
functions.Arguments
first_lane
,last_lane
, andmember_mask
are ignored inShuffle*
functions.
Utilities:
SwizzleScanOp
,ReduceBySegmentOp
,ReduceByKeyOp
,CastOp
are not supported.