rocRAND precision support

This topic discusses the various data types supported by rocRAND and provides a comparison with the data type support in NVIDIA CUDA cuRAND.

This page lists the data types supported by the library itself and does not indicate hardware support. A type listed here is only usable if the GPU architecture also supports it; otherwise it is unsupported. For data type support across the other ROCm libraries and by GPU architecture, see the Data types and precision support page.

Output type support

As a random number generation library, rocRAND specifies only the output data types for the random values it generates; it has no input data types. The following table summarizes the output data types supported by rocRAND. For the per-generator and per-distribution detail, including the comparison with cuRAND, see the sections that follow.

Data type	Support
int8	Output only
int16	Output only
int32	Output only
int64	Output only
float16	Output only
float32	Output only
float64	Output only

Host API

This section covers the data types supported for the host API. The icons representing different levels of support are explained in the following table.

Icon	Definition
NA	Not applicable
❌	Not supported
⚠️	Partial support
✅	Full support

Generator types

Supported generators on the host

Generator	rocRAND support	cuRAND support
XORWOW	✅	✅
MRG32K3A	✅	✅
MTGP32	✅	✅
Philox 4x32-10	✅	✅
MT19937	✅	✅
MRG31K3P	✅	❌
LFSR113	✅	❌
ThreeFry 2x32-20	✅	❌
ThreeFry 4x32-20	✅	❌
ThreeFry 2x64-20	✅	❌
ThreeFry 4x64-20	✅	❌
Sobol32	✅	✅
Scrambled Sobol32	✅	✅
Sobol64	✅	✅
Scrambled Sobol64	✅	✅

Only Sobol64, Scrambled Sobol64, ThreeFry 2x64-20, and ThreeFry 4x64-20 support the generation of 64-bit unsigned long long int integers. The other generators generate 32-bit unsigned int integers.

Seed types

All generators can be seeded with unsigned long long. However, LFSR113 can also be seeded using a uint4.

Output types

The generators produce pseudo-random numbers chosen from a given distribution. The following distributions and corresponding output types are supported for the host API:

Uniform distribution

Supported types for uniform distributions on the host

Type	Size of type	rocRAND support	cuRAND support
unsigned char	8 bit	✅	❌
unsigned short	16 bit	✅	❌
unsigned int	32 bit	✅	✅
unsigned long long	64 bit (see note)	✅	✅
half	16 bit	✅	❌
float	32 bit	✅	✅
double	64 bit	✅	✅

Uniform distributions of integral types return a number between 0 and 2^(size in bits) - 1, whereas floating-point types return a number between 0.0 and 1.0, excluding 1.0.

Note

The generation of 64-bit unsigned long long integers is only supported by 64-bit generators (Scrambled Sobol 64, Sobol64, Threefry 2x64-20, and Threefry 4x64-20).

Poisson distribution

Supported types for the Poisson distribution on the host

Type	Size of type	rocRAND support	cuRAND support
unsigned int	32 bit	✅	✅

Normal distribution

Supported types for normal distributions on the host

Type	Size of type	rocRAND support	cuRAND support
half	16 bit	✅	❌
float	32 bit	✅	✅
double	64 bit	✅	✅

Log-normal distributions

Supported types for log-normal distributions on the host

Type	Size of type	rocRAND support	cuRAND support
half	16 bit	✅	❌
float	32 bit	✅	✅
double	64 bit	✅	✅

Device API

This section covers the supported data types for the device API.

Generator types

Supported generators on the device

Generator	rocRAND support	cuRAND support
XORWOW	✅	✅
MRG32K3A	✅	✅
MTGP32	✅	✅
Philox 4x32-10	✅	✅
MT19937	❌	❌
MRG31K3P	✅	❌
LFSR113	✅	❌
ThreeFry 2x32-20	✅	❌
ThreeFry 4x32-20	✅	❌
ThreeFry 2x64-20	✅	❌
ThreeFry 4x64-20	✅	❌
Sobol32	✅	✅
Scrambled Sobol32	✅	✅
Sobol64	✅	✅
Scrambled Sobol64	✅	✅

Seed types

All generators can be seeded with unsigned long long, however LFSR113 can also be seeded using an uint4.

Output types

The generators produce pseudo-random numbers chosen from a given distribution. The following distributions and corresponding output types are supported for the device API. However, not all generators support all types.

Uniform distribution

Supported types for uniform distributions on the device

Type	rocRAND support	Supported rocRAND generators	cuRAND support
unsigned int	✅	All native 32-bit generators	✅
unsigned long long int	✅	All native 64-bit generators	✅
float	✅	All generators	✅
float2	✅	Philox 4x32-10	❌
float4	✅	Philox 4x32-10	✅
double	✅	All generators	✅
double2	✅	Philox 4x32-10	✅
double4	✅	Philox 4x32-10	❌

Normal distribution

Supported types for normal distributions on the device

Type	rocRAND support	Supported rocRAND generators	cuRAND support
float	✅	All generators	✅
float2	✅	Philox 4x32-10, MRG31K3P, MRG32K3A, XORWOW, LFSR113, all ThreeFry generators	✅
float4	✅	Philox 4x32-10	✅
double	✅	All generators	✅
double2	✅	Philox 4x32-10, MRG31K3P, MRG32K3A, XORWOW, LFSR113, all ThreeFry generators	✅
double4	✅	Philox 4x32-10	❌

Log-normal distributions

Supported types for log-normal distributions on the device

Type	rocRAND support	Supported rocRAND generators	cuRAND support
float	✅	All generators	✅
float2	✅	Philox 4x32-10, MRG31K3P, MRG32K3A, XORWOW, LFSR113, all ThreeFry generators	✅
float4	✅	Philox 4x32-10	✅
double	✅	All generators	✅
double2	✅	Philox 4x32-10, MRG31K3P, MRG32K3A, XORWOW, LFSR113, all ThreeFry generators	✅
double4	✅	Philox 4x32-10	❌

Poisson distributions

Supported types for Poisson distributions on the device

Type	rocRAND support	Supported rocRAND generators	cuRAND support
unsigned int	✅	Philox 4x32-10, MRG31k3p, MRG32K3A, XORWOW, MTGP32, Sobol32, Scrambled Sobol32, LFSR113, all ThreeFry generators	✅
unsigned long long int	✅	Sobol64, Scrambled Sobol64	❌
uint4	✅	Philox 4x32-10	✅

Discrete distributions

Supported types for discrete distributions on the device

Type	rocRAND support	Supported rocRAND generators	cuRAND support
unsigned int	✅	All generators	✅
uint4	✅	Philox 4x32-10	✅ - only Philox - 4x32-10