Atomic Functions
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:

Atomics are 64 bit integers.

Atomics can be represented as either signed or unsigned.

Atomics wrap around at overflow and underflow operations.

All operations guarantee atomicity. No intermediate results can be seen. The result of one mutation can only be the input to one following mutation.

All atomic operations are mutually ordered. If atomic B is updated after atomic A, then that is how it will appear to any concurrent readers. No one can read the new value of B and then read the old value of A.

Indexes into atomic arrays are onebased. An atomic array of arity N contains N atomics with index from 1 to N.
Functions
new(Arity, Opts) > atomics_ref()
Arity = integer() >= 1
Opts = [Opt]
Opt = {signed, boolean()}
Create a new atomic array of
atomics.
Argument
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.
add_get(Ref, Ix, Incr) > integer()
Ref = atomics_ref()
Ix = Incr = integer()
Atomic addition and return of the result.
sub_get(Ref, Ix, Decr) > integer()
Ref = atomics_ref()
Ix = Decr = integer()
Atomic subtraction and return of the result.
exchange(Ref, Ix, Desired) > integer()
Ref = atomics_ref()
Ix = Desired = integer()
Atomically replaces the value of the atomic with
and returns the value it held
previously.
compare_exchange(Ref, Ix, Expected, Desired) > ok  integer()
Ref = atomics_ref()
Ix = Expected = Desired = integer()
Atomically compares the atomic with
,
and if those are equal, set atomic to
.
Returns ok
if
was written. Returns
the actual atomic value if not equal to
.
info(Ref) > Info
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.