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8.30 ATOMIC_CAS — Atomic compare and swap ¶

Description:

ATOMIC_CAS compares the variable ATOM with the value of COMPARE; if the value is the same, ATOM is set to the value of NEW. Additionally, OLD is set to the value of ATOM that was used for the comparison. When STAT is present and the invocation was successful, it is assigned the value 0. If it is present and the invocation has failed, it is assigned a positive value; in particular, for a coindexed ATOM, if the remote image has stopped, it is assigned the value of ISO_FORTRAN_ENV’s STAT_STOPPED_IMAGE and if the remote image has failed, the value STAT_FAILED_IMAGE.

Standard:

TS 18508 or later

Class:

Atomic subroutine

Syntax:

CALL ATOMIC_CAS (ATOM, OLD, COMPARE, NEW [, STAT])

Arguments:

ATOM	Scalar coarray or coindexed variable of either integer type with ATOMIC_INT_KIND kind or logical type with ATOMIC_LOGICAL_KIND kind.
OLD	Scalar of the same type and kind as ATOM.
COMPARE	Scalar variable of the same type and kind as ATOM.
NEW	Scalar variable of the same type as ATOM. If kind is different, the value is converted to the kind of ATOM.
STAT	(optional) Scalar default-kind integer variable.

Example:

program atomic
  use iso_fortran_env
  logical(atomic_logical_kind) :: atom[*], prev
  call atomic_cas (atom[1], prev, .false., .true.))
end program atomic

See also:

ATOMIC_DEFINE — Setting a variable atomically, ATOMIC_REF — Obtaining the value of a variable atomically, ISO_FORTRAN_ENV