atomics.3erl man page

atomics — Atomic Functions

Description

This module provides a set of functions to do atomic operations towards mutable atomic variables. The implementation utilizes only atomic hardware instructions without any software level locking, which makes it very efficient for concurrent access. The atomics are organized into arrays with the following semantics:

Data Types

atomics_ref()

Identifies an atomic array returned from new/2.

Exports

new(Arity, Opts) -> atomics_ref()
Types:

Arity = integer() >= 1
Opts = [Opt]
Opt = {signed, boolean()}

Create a new atomic array of Arity atomics.

Argument Opts is a list of the following possible options:

{signed, boolean()}:

Indicate if the elements of the array will be treated as signed or unsigned integers. Default is true (signed).

The integer interval for signed atomics are from -(1 bsl 63) to (1 bsl 63)-1 and for unsigned atomics from 0 to (1 bsl 64)-1.

Atomics are not tied to the current process and are automatically garbage collected when they are no longer referenced.

put(Ref, Ix, Value) -> ok
Types:

Ref = atomics_ref()
Ix = Value = integer()

Set atomic to Value.

get(Ref, Ix) -> integer()
Types:

Ref = atomics_ref()
Ix = integer()

Read atomic value.

add(Ref, Ix, Incr) -> ok
Types:

Ref = atomics_ref()
Ix = Incr = integer()

Add Incr to atomic.

add_get(Ref, Ix, Incr) -> integer()
Types:

Ref = atomics_ref()
Ix = Incr = integer()

Atomic addition and return of the result.

sub(Ref, Ix, Decr) -> ok
Types:

Ref = atomics_ref()
Ix = Decr = integer()

Subtract Decr from atomic.

sub_get(Ref, Ix, Decr) -> integer()
Types:

Ref = atomics_ref()
Ix = Decr = integer()

Atomic subtraction and return of the result.

exchange(Ref, Ix, Desired) -> integer()
Types:

Ref = atomics_ref()
Ix = Desired = integer()

Atomically replaces the value of the atomic with Desired and returns the value it held previously.

compare_exchange(Ref, Ix, Expected, Desired) -> ok | integer()
Types:

Ref = atomics_ref()
Ix = Expected = Desired = integer()

Atomically compares the atomic with Expected, and if those are equal, set atomic to Desired. Returns ok if Desired was written. Returns the actual atomic value if not equal to Expected.

info(Ref) -> Info
Types:

Ref = atomics_ref()
Info =
   #{size := Size, max := Max, min := Min, memory := Memory}
Size = integer() >= 0
Max = Min = integer()
Memory = integer() >= 0

Return information about an atomic array in a map. The map has the following keys:

size:

The number of atomics in the array.

max:

The highest possible value an atomic in this array can hold.

min:

The lowest possible value an atomic in this array can hold.

memory:

Approximate memory consumption for the array in bytes.

Info

erts 10.4.4 Ericsson AB Erlang Module Definition