C Library Functions  - atomic_xor (3)

NAME

ATOMIC_XOR(3) - [ATOMIC:BIT MANIPULATION] Atomically perform a bitwise XOR operation

SYNOPSIS

call atomic_xor(atom, value [,stat] ) 

         subroutine atomic_xor(atom,value,stat)


          integer(atomic_int_kind)            :: atom[*]
          integer(atomic_int_kind),intent(in) :: value
          integer,intent(out),intent(out)     :: stat

CHARACTERISTICS

o ATOM is a scalar coarray or coindexed variable of integer type with atomic_int_kind kind.
o VALUE is a scalar of the same type as ATOM. If the kind is different, the value is converted to the kind of ATOM.
o STAT is a Scalar default-kind integer variable.

CHARACTERISTICS

DESCRIPTION

ATOMIC_XOR(ATOM, VALUE, STAT) atomically performs a bitwise XOR operation between the value of ATOM and VALUE, storing the result in ATOM.

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.

Unlike ATOMIC_FETCH_XOR, this does not return the previous value.

Use for toggling bits atomically.

OPTIONS

o ATOM : Scalar coarray or coindexed variable of integer type with atomic_int_kind kind.
o VALUE : Scalar of the same type as ATOM. If the kind is different, the value is converted to the kind of ATOM.
o STAT : (optional) Scalar default-kind integer variable. Set to 0 on success, or a positive value on failure.

EXAMPLES

Sample program: 

    program demo_atomic_xor
      use iso_fortran_env
      implicit none
      integer(atomic_int_kind) :: flags[*]
      integer :: stat, me


      if (this_image() == 1) flags = int(b’1100’, atomic_int_kind)
      sync all


      me = this_image()
      call atomic_xor(flags[1], int(b’1010’, atomic_int_kind), stat)


      if (stat /= 0) print *, "Image", me, ": Failed with STAT =", stat
      sync all


      if (this_image() == 1) print *, "Final flags:", flags
    end program demo_atomic_xor
Expected Output (4 images) 

        > Final flags: 6

STANDARD

TS 18508

SEE ALSO

ATOMIC_DEFINE(3), ATOMIC_FETCH_XOR(3), ISO_FORTRAN_ENV(3), ATOMIC_ADD(3), ATOMIC_OR(3), ATOMIC_XOR(3)

See ISO_FORTRAN_ENV for constants like ATOMIC_INT_KIND, STAT_STOPPED_IMAGE, and STAT_FAILED_IMAGE.

Fortran intrinsic descriptions

Nemo Release 3.1 atomic_xor (3) June 29, 2025
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