Atomic Memory Operations

An AMO is a one-sided communication mechanism that combines memory read, update, or write operations with atomicity guarantees described in Section  Atomicity Guarantees. Similar to the RMA routines, described in Section Remote Memory Access, the AMOs are performed only on symmetric objects. NVSHMEM defines two types of AMO routines:

• The fetching routines return the original value of, and optionally update, the remote data object in a single atomic operation. The routines return after the data has been fetched from the target PE and delivered to the calling PE. The data type of the returned value is the same as the type of the remote data object.

• The non-fetching routines update the remote data object in a single atomic operation. A call to a non-fetching atomic routine issues the atomic operation and may return before the operation executes on the target PE. The nvshmem_quiet, shmem_barrier, or shmem_barrier_all routines can be used to force completion for these non-fetching atomic routines.

  The non-fetching routines include:

NVSHMEM provides AMO interfaces with the following types:

Standard AMO Types and Names

TYPE	TYPENAME
int	int
long	long
long long	longlong
size_t	size
ptrdiff_t	ptrdiff

Extended AMO Types and Names

TYPE	TYPENAME
float	float
double	double
int	int
long	long
long long	longlong
size_t	size
ptrdiff_t	ptrdiff

Bitwise AMO Types and Names

TYPE	TYPENAME
unsigned int	uint
unsigned long	ulong
unsigned long long	ulonglong
int32_t	int32
int64_t	int64
uint32_t	uint32
uint64_t	uint64

NVSHMEM_ATOMIC_FETCH

TYPE nvshmem_TYPENAME_atomic_fetch(const TYPE *source, int pe)

__device__ TYPE nvshmem_TYPENAME_atomic_fetch(const TYPE *source, int pe)

where TYPE is one of the extended AMO types and has a corresponding TYPENAME specified by Table Extended AMO Types and Names.

TYPE nvshmem_fetch(const TYPE *source, int pe)

__device__ TYPE nvshmem_fetch(const TYPE *source, int pe)

where TYPE is one of {float, double, int, long, long long}.

TYPE nvshmem_TYPENAME_fetch(const TYPE *source, int pe)

__device__ TYPE nvshmem_TYPENAME_fetch(const TYPE *source, int pe)

where TYPE is one of {float, double, int, long, long long} and has a corresponding TYPENAME specified by Table Extended AMO Types and Names.

source [IN]

Symmetric address of the source data object. The type of source should match that implied in the SYNOPSIS section.

pe [IN]

An integer that indicates the PE number from which source is to be fetched.

Description

nvshmem_atomic_fetch performs an atomic fetch operation. It returns the contents of the source as an atomic operation.

Returns

The contents at the source address on the remote PE. The data type of the return value is the same as the type of the remote data object.

NVSHMEM_ATOMIC_SET

void nvshmem_TYPENAME_atomic_set(TYPE *dest, TYPE value, int pe)

__device__ void nvshmem_TYPENAME_atomic_set(TYPE *dest, TYPE value, int pe)

where TYPE is one of the extended AMO types and has a corresponding TYPENAME specified by Table Extended AMO Types and Names.

void nvshmem_set(TYPE *dest, TYPE value, int pe)

__device__ void nvshmem_set(TYPE *dest, TYPE value, int pe)

where TYPE is one of {float, double, int, long, long long}.

void nvshmem_TYPENAME_set(TYPE *dest, TYPE value, int pe)

__device__ void nvshmem_TYPENAME_set(TYPE *dest, TYPE value, int pe)

where TYPE is one of {float, double, int, long, long long} and has a corresponding TYPENAME specified by Table Extended AMO Types and Names.

dest [OUT]

Symmetric address of the destination data object. The type of dest should match that implied in the SYNOPSIS section.

value [IN]

The operand to the atomic set operation. The type of value should match that implied in the SYNOPSIS section.

pe [IN]

An integer that indicates the PE number on which dest is to be updated.

Description

nvshmem_atomic_set performs an atomic set operation. It writes the value into dest on pe as an atomic operation.

Returns

None.

NVSHMEM_ATOMIC_COMPARE_SWAP

TYPE nvshmem_TYPENAME_atomic_compare_swap(TYPE *dest, TYPE cond, TYPE value, int pe)

__device__ TYPE nvshmem_TYPENAME_atomic_compare_swap(TYPE *dest, TYPE cond, TYPE value, int pe)

where TYPE is one of the standard AMO types and has a corresponding TYPENAME specified by Table Standard AMO Types and Names.

TYPE nvshmem_cswap(TYPE *dest, TYPE cond, TYPE value, int pe)

__device__ TYPE nvshmem_cswap(TYPE *dest, TYPE cond, TYPE value, int pe)

where TYPE is one of {int, long, long long}.

TYPE nvshmem_TYPENAME_cswap(TYPE *dest, TYPE cond, TYPE value, int pe)

__device__ TYPE nvshmem_TYPENAME_cswap(TYPE *dest, TYPE cond, TYPE value, int pe)

where TYPE is one of {int, long, long long} and has a corresponding TYPENAME specified by Table Standard AMO Types and Names.

dest [OUT]

Symmetric address of the destination data object. The type of dest should match that implied in the SYNOPSIS section.

cond [IN]

cond is compared to the remote dest value. If cond and the remote dest are equal, then value is swapped into the remote dest; otherwise, the remote dest is unchanged. In either case, the old value of the remote dest is returned as the routine return value. cond must be of the same data type as dest.

value [IN]

The value to be atomically written to the remote PE. The type of value should match that implied in the SYNOPSIS section.

pe [IN]

An integer that indicates the PE number upon which dest is to be updated.

Description

The conditional swap routines conditionally update a dest data object on the specified PE and return the prior contents of the data object in one atomic operation.

Returns

The contents that had been in the dest data object on the remote PE prior to the conditional swap. Data type is the same as the dest data type.

NVSHMEM_ATOMIC_SWAP

TYPE nvshmem_TYPENAME_atomic_swap(TYPE *dest, TYPE value, int pe)

__device__ TYPE nvshmem_TYPENAME_atomic_swap(TYPE *dest, TYPE value, int pe)

where TYPE is one of the extended AMO types and has a corresponding TYPENAME specified by Table Extended AMO Types and Names.

TYPE nvshmem_swap(TYPE *dest, TYPE value, int pe)

__device__ TYPE nvshmem_swap(TYPE *dest, TYPE value, int pe)

where TYPE is one of {float, double, int, long, long long}.

TYPE nvshmem_TYPENAME_swap(TYPE *dest, TYPE value, int pe)

__device__ TYPE nvshmem_TYPENAME_swap(TYPE *dest, TYPE value, int pe)

where TYPE is one of {float, double, int, long, long long} and has a corresponding TYPENAME specified by Table Extended AMO Types and Names.

dest [OUT]

Symmetric address of the destination data object. The type of dest should match that implied in the SYNOPSIS section.

value [IN]

The value to be atomically written to the remote PE. The type of value should match that implied in the SYNOPSIS section.

pe [IN]

An integer that indicates the PE number on which dest is to be updated.

Description

nvshmem_atomic_swap performs an atomic swap operation. It writes value into dest on PE and returns the previous contents of dest as an atomic operation.

Returns

The content that had been at the dest address on the remote PE prior to the swap is returned.

NVSHMEM_ATOMIC_FETCH_INC

TYPE nvshmem_TYPENAME_atomic_fetch_inc(TYPE *dest, int pe)

__device__ TYPE nvshmem_TYPENAME_atomic_fetch_inc(TYPE *dest, int pe)

where TYPE is one of the standard AMO types and has a corresponding TYPENAME specified by Table Standard AMO Types and Names.

TYPE nvshmem_finc(TYPE *dest, int pe)

__device__ TYPE nvshmem_finc(TYPE *dest, int pe)

where TYPE is one of {int, long, long long}.

TYPE nvshmem_TYPENAME_finc(TYPE *dest, int pe)

__device__ TYPE nvshmem_TYPENAME_finc(TYPE *dest, int pe)

where TYPE is one of {int, long, long long} and has a corresponding TYPENAME specified by Table Standard AMO Types and Names.

dest [OUT]

Symmetric address of the destination data object. The type of dest should match that implied in the SYNOPSIS section.

pe [IN]

An integer that indicates the PE number on which dest is to be updated.

Description

These routines perform a fetch-and-increment operation. The dest on PE pe is increased by one and the routine returns the previous contents of dest as an atomic operation.

Returns

The contents that had been at the dest address on the remote PE prior to the increment. The data type of the return value is the same as the dest.

NVSHMEM_ATOMIC_INC

void nvshmem_TYPENAME_atomic_inc(TYPE *dest, int pe)

__device__ void nvshmem_TYPENAME_atomic_inc(TYPE *dest, int pe)

where TYPE is one of the standard AMO types and has a corresponding TYPENAME specified by Table Standard AMO Types and Names.

void nvshmem_inc(TYPE *dest, int pe)

__device__ void nvshmem_inc(TYPE *dest, int pe)

where TYPE is one of {int, long, long long}.

void nvshmem_TYPENAME_inc(TYPE *dest, int pe)

__device__ void nvshmem_TYPENAME_inc(TYPE *dest, int pe)

where TYPE is one of {int, long, long long} and has a corresponding TYPENAME specified by Table Standard AMO Types and Names.

dest [OUT]

Symmetric address of the destination data object. The type of dest should match that implied in the SYNOPSIS section.

pe [IN]

An integer that indicates the PE number on which dest is to be updated.

Description

These routines perform an atomic increment operation on the dest data object on PE.

Returns

None.

NVSHMEM_ATOMIC_FETCH_ADD

TYPE nvshmem_TYPENAME_atomic_fetch_add(TYPE *dest, TYPE value, int pe)

__device__ TYPE nvshmem_TYPENAME_atomic_fetch_add(TYPE *dest, TYPE value, int pe)

where TYPE is one of the standard AMO types and has a corresponding TYPENAME specified by Table Standard AMO Types and Names.

TYPE nvshmem_fadd(TYPE *dest, TYPE value, int pe)

__device__ TYPE nvshmem_fadd(TYPE *dest, TYPE value, int pe)

where TYPE is one of {int, long, long long}.

TYPE nvshmem_TYPENAME_fadd(TYPE *dest, TYPE value, int pe)

__device__ TYPE nvshmem_TYPENAME_fadd(TYPE *dest, TYPE value, int pe)

where TYPE is one of {int, long, long long} and has a corresponding TYPENAME specified by Table Standard AMO Types and Names.

dest [OUT]

Symmetric address of the destination data object. The type of dest should match that implied in the SYNOPSIS section.

value [IN]

The operand to the atomic fetch-and-add operation. The type of value should match that implied in the SYNOPSIS section.

pe [IN]

An integer that indicates the PE number on which dest is to be updated.

Description

nvshmem_atomic_fetch_add routines perform an atomic fetch-and-add operation. An atomic fetch-and-add operation fetches the old dest and adds value to dest without the possibility of another atomic operation on the dest between the time of the fetch and the update. These routines add value to dest on pe and return the previous contents of dest as an atomic operation.

Returns

The contents that had been at the dest address on the remote PE prior to the atomic addition operation. The data type of the return value is the same as the dest.

NVSHMEM_ATOMIC_ADD

void nvshmem_TYPENAME_atomic_add(TYPE *dest, TYPE value, int pe)

__device__ void nvshmem_TYPENAME_atomic_add(TYPE *dest, TYPE value, int pe)

where TYPE is one of the standard AMO types and has a corresponding TYPENAME specified by Table Standard AMO Types and Names.

void nvshmem_add(TYPE *dest, TYPE value, int pe)

__device__ void nvshmem_add(TYPE *dest, TYPE value, int pe)

where TYPE is one of {int, long, long long}.

void nvshmem_TYPENAME_add(TYPE *dest, TYPE value, int pe)

__device__ void nvshmem_TYPENAME_add(TYPE *dest, TYPE value, int pe)

where TYPE is one of {int, long, long long} and has a corresponding TYPENAME specified by Table Standard AMO Types and Names.

dest [OUT]

Symmetric address of the destination data object. The type of dest should match that implied in the SYNOPSIS section.

value [IN]

The operand to the atomic add operation. The type of value should match that implied in the SYNOPSIS section.

pe [IN]

An integer that indicates the PE number upon which dest is to be updated.

Description

The nvshmem_atomic_add routine performs an atomic add operation. It adds value to dest on PE pe and atomically updates the dest without returning the value.

Returns

None.

NVSHMEM_ATOMIC_FETCH_AND

TYPE nvshmem_TYPENAME_atomic_fetch_and(TYPE *dest, TYPE value, int pe)

__device__ TYPE nvshmem_TYPENAME_atomic_fetch_and(TYPE *dest, TYPE value, int pe)

where TYPE is one of the bitwise AMO types and has a corresponding TYPENAME specified by Table Bitwise AMO Types and Names.

dest [OUT]

Symmetric address of the destination data object. The type of dest should match that implied in the SYNOPSIS section.

value [IN]

The operand to the bitwise AND operation. The type of value should match that implied in the SYNOPSIS section.

pe [IN]

An integer value for the PE on which dest is to be updated.

Description

nvshmem_atomic_fetch_and atomically performs a fetching bitwise AND on the remotely accessible data object pointed to by dest at PE pe with the operand value.

Returns

The value pointed to by dest on PE pe immediately before the operation is performed.

NVSHMEM_ATOMIC_AND

void nvshmem_TYPENAME_atomic_and(TYPE *dest, TYPE value, int pe)

__device__ void nvshmem_TYPENAME_atomic_and(TYPE *dest, TYPE value, int pe)

where TYPE is one of the bitwise AMO types and has a corresponding TYPENAME specified by Table Bitwise AMO Types and Names.

dest [OUT]

Symmetric address of the destination data object. The type of dest should match that implied in the SYNOPSIS section.

value [IN]

The operand to the bitwise AND operation. The type of value should match that implied in the SYNOPSIS section.

pe [IN]

An integer value for the PE on which dest is to be updated.

Description

nvshmem_atomic_and atomically performs a non-fetching bitwise AND on the remotely accessible data object pointed to by dest at PE pe with the operand value.

Returns

None.

NVSHMEM_ATOMIC_FETCH_OR

TYPE nvshmem_TYPENAME_atomic_fetch_or(TYPE *dest, TYPE value, int pe)

__device__ TYPE nvshmem_TYPENAME_atomic_fetch_or(TYPE *dest, TYPE value, int pe)

where TYPE is one of the bitwise AMO types and has a corresponding TYPENAME specified by Table Bitwise AMO Types and Names.

dest [OUT]

Symmetric address of the destination data object. The type of dest should match that implied in the SYNOPSIS section.

value [IN]

The operand to the bitwise OR operation. The type of value should match that implied in the SYNOPSIS section.

pe [IN]

An integer value for the PE on which dest is to be updated.

Description

nvshmem_atomic_fetch_or atomically performs a fetching bitwise OR on the remotely accessible data object pointed to by dest at PE pe with the operand value.

Returns

The value pointed to by dest on PE pe immediately before the operation is performed.

NVSHMEM_ATOMIC_OR

void nvshmem_TYPENAME_atomic_or(TYPE *dest, TYPE value, int pe)

__device__ void nvshmem_TYPENAME_atomic_or(TYPE *dest, TYPE value, int pe)

where TYPE is one of the bitwise AMO types and has a corresponding TYPENAME specified by Table Bitwise AMO Types and Names.

dest [OUT]

Symmetric address of the destination data object. The type of dest should match that implied in the SYNOPSIS section.

value [IN]

The operand to the bitwise OR operation. The type of value should match that implied in the SYNOPSIS section.

pe [IN]

An integer value for the PE on which dest is to be updated.

Description

nvshmem_atomic_or atomically performs a non-fetching bitwise OR on the remotely accessible data object pointed to by dest at PE pe with the operand value.

Returns

None.

NVSHMEM_ATOMIC_FETCH_XOR

TYPE nvshmem_TYPENAME_atomic_fetch_xor(TYPE *dest, TYPE value, int pe)

__device__ TYPE nvshmem_TYPENAME_atomic_fetch_xor(TYPE *dest, TYPE value, int pe)

where TYPE is one of the bitwise AMO types and has a corresponding TYPENAME specified by Table Bitwise AMO Types and Names.

dest [OUT]

Symmetric address of the destination data object. The type of dest should match that implied in the SYNOPSIS section.

value [IN]

The operand to the bitwise XOR operation. The type of value should match that implied in the SYNOPSIS section.

pe [IN]

An integer value for the PE on which dest is to be updated.

Description

nvshmem_atomic_fetch_xor atomically performs a fetching bitwise XOR on the remotely accessible data object pointed to by dest at PE pe with the operand value.

Returns

The value pointed to by dest on PE pe immediately before the operation is performed.

NVSHMEM_ATOMIC_XOR

void nvshmem_TYPENAME_atomic_xor(TYPE *dest, TYPE value, int pe)

__device__ void nvshmem_TYPENAME_atomic_xor(TYPE *dest, TYPE value, int pe)

where TYPE is one of the bitwise AMO types and has a corresponding TYPENAME specified by Table Bitwise AMO Types and Names.

dest [OUT]

Symmetric address of the destination data object. The type of dest should match that implied in the SYNOPSIS section.

value [IN]

The operand to the bitwise XOR operation. The type of value should match that implied in the SYNOPSIS section.

pe [IN]

An integer value for the PE on which dest is to be updated.

Description

nvshmem_atomic_xor atomically performs a non-fetching bitwise XOR on the remotely accessible data object pointed to by dest at PE pe with the operand value.

Returns

None.