ISO/IEC TS 18508:2015
(Main)Information technology — Additional Parallel Features in Fortran
Information technology — Additional Parallel Features in Fortran
ISO/IEC TS 18508:2015 specifies the form and establishes the interpretation of facilities that extend the For-tran language defined by ISO/IEC 1539-1:2010, ISO/IEC 1539-1:2010/Cor 1:2012, and ISO/IEC 1539-1:2010/Cor 2:2013. The purpose of this Technical Specification is to promote portability, reliability, maintainability, and ef-ficient execution of parallel programs written in Fortran, for use on a variety of computing systems. ISO/IEC TS 18508:2015 does not specify formal data consistency model. Developing the formal data consist-ency model is left until the integration of these facilities into ISO/IEC 1539-1.
Technologies de l'information — Caractéristiques parallèles supplémentaires en Fortran
General Information
Standards Content (Sample)
TECHNICAL ISO/IEC TS
SPECIFICATION 18508
First edition
2015-12-01
Information technology — Additional
Parallel Features in Fortran
Technologies de l’information — Caractéristiques parallèles
supplémentaires en Fortran
Reference number
ISO/IEC TS 18508:2015(E)
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ISO/IEC TS 18508:2015(E)
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ISO/IEC TS 18508:2015(E)
Contents
1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3 Terms and de nitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1 New intrinsic procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2 Fortran 2008 compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5 Teams of images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1 Team concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.2 TEAM TYPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.3 CHANGE TEAM construct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.4 Image selectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.5 FORM TEAM statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.6 SYNC TEAM statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6 Failed images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.2 FAIL IMAGE statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.3 CRITICAL construct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.4 STAT FAILED IMAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7 Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.2 EVENT TYPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.3 EVENT POST statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.4 EVENT WAIT statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8 Intrinsic procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.2 Atomic subroutines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.3 Collective subroutines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.4 New intrinsic procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.4.1 ATOMIC ADD (ATOM, VALUE [, STAT]) . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.4.2 ATOMIC AND (ATOM, VALUE [, STAT]) . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.4.3 ATOMIC CAS (ATOM, OLD, COMPARE, NEW [, STAT]) . . . . . . . . . . . . . . . . 22
8.4.4 ATOMIC FETCH ADD (ATOM, VALUE, OLD [, STAT]) . . . . . . . . . . . . . . . . . 22
8.4.5 ATOMIC FETCH AND (ATOM, VALUE, OLD [, STAT]) . . . . . . . . . . . . . . . . . 22
8.4.6 ATOMIC FETCH OR (ATOM, VALUE, OLD [, STAT]) . . . . . . . . . . . . . . . . . . 23
8.4.7 ATOMIC FETCH XOR (ATOM, VALUE, OLD [, STAT]) . . . . . . . . . . . . . . . . . 23
8.4.8 ATOMIC OR (ATOM, VALUE [, STAT]) . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.4.9 ATOMIC XOR (ATOM, VALUE [, STAT]) . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.4.10 CO BROADCAST (A, SOURCE IMAGE [, STAT, ERRMSG]) . . . . . . . . . . . . . . 24
8.4.11 CO MAX (A [, RESULT IMAGE, STAT, ERRMSG]) . . . . . . . . . . . . . . . . . . . . 25
8.4.12 CO MIN (A [, RESULT IMAGE, STAT, ERRMSG]) . . . . . . . . . . . . . . . . . . . . 25
8.4.13 CO REDUCE (A, OPERATOR [, RESULT IMAGE, STAT, ERRMSG]) . . . . . . . . . 26
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8.4.14 CO SUM (A [, RESULT IMAGE, STAT, ERRMSG]) . . . . . . . . . . . . . . . . . . . . 27
8.4.15 EVENT QUERY ( EVENT, COUNT [, STAT]) . . . . . . . . . . . . . . . . . . . . . . . 27
8.4.16 FAILED IMAGES ([TEAM, KIND]) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8.4.17 GET TEAM ([LEVEL]) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8.4.18 IMAGE STATUS (IMAGE, [TEAM]) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
8.4.19 STOPPED IMAGES ([TEAM, KIND]) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
8.4.20 TEAM NUMBER ([TEAM]) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.5 Modi ed intrinsic procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.5.1 ATOMIC DEFINE and ATOMIC REF . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.5.2 IMAGE INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.5.3 MOVE ALLOC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.5.4 NUM IMAGES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.5.5 THIS IMAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
9 Required editorial changes to ISO/IEC 1539-1:2010(E) . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
9.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
9.2 Edits to Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
9.3 Edits to clause 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
9.4 Edits to clause 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
9.5 Edits to clause 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
9.6 Edits to clause 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
9.7 Edits to clause 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
9.8 Edits to clause 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
9.9 Edits to clause 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
9.10 Edits to clause 16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
9.11 Edits to annex A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
9.12 Edits to annex C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Annex A (informative) Extended notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
A.1 Clause 5 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
A.1.1 Example using three teams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
A.1.2 Accessing coarrays in sibling teams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
A.1.3 Reducing the codimension of a coarray . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
A.2 Clause 6 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
A.2.1 Example involving failed images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
A.3 Clause 7 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
A.3.1 EVENT QUERY example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
A.3.2 EVENT QUERY example that tolerates image failure . . . . . . . . . . . . . . . . . . . . 50
A.3.3 EVENTS example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
A.4 Clause 8 notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
A.4.1 Collective subroutine examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
A.4.2 Atomic memory consistency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
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Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commis-
sion) form the specialized system for worldwide standardization. National bodies that are members of ISO or
IEC participate in the development of International Standards through technical committees established by the
respective organization to deal with particular elds of technical activity. ISO and IEC technical committees
collaborate in elds of mutual interest. Other international organizations, governmental and nongovernmental,
in liaison with ISO and IEC, also take part in the work. In the eld of information technology, ISO and IEC have
established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International Stand-
ards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the national bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, the joint
technical committee may decide to publish an ISO/IEC Technical Speci cation (ISO/IEC TS), which represents
an agreement between the members of the joint technical committee and is accepted for publication if it is
approved by 2/3 of the members of the committee casting a vote.
An ISO/IEC TS is reviewed after three years in order to decide whether it will be con rmed for a further three
years, revised to become an International Standard, or withdrawn. If the ISO/IEC TS is con rmed, it is reviewed
again after a further three years, at which time it must either be transformed into an International Standard or
be withdrawn.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
ISO/IEC TS 18508:2015 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC22, Programming languages, their environments and system software interfaces.
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Introduction
The system for parallel programming in Fortran, as standardized by ISO/IEC 1539-1:2010, de nes simple syntax
for access to data on another image of a program, synchronization statements for controlling the ordering of
execution segments between images, and collective allocation and deallocation of memory on all images.
The existing system for parallel programming does not provide for an environment where a subset of the images
can easily work on part of an application while not a ecting other images in the program. This complicates
development of independent parts of an application by separate teams of programmers. The existing system
does not provide a mechanism for a processor to identify what images have failed during execution of a program.
This adversely a ects the resilience of programs executing on large systems. The synchronization primitives
available in the existing system do not provide a convenient mechanism for ordering execution segments on
di erent images without requiring that those images arrive at a synchronization point before either is allowed to
proceed. This introduces unnecessary ineciency into programs. Finally, the existing system does not provide
intrinsic procedures for commonly used collective and atomic memory operations. Intrinsic procedures for these
operations can be highly optimized for the target computational system, providing signi cantly improved program
performance.
This Technical Speci cation extends the facilites of Fortran for parallel programming to provide for grouping the
images of a program into nonoverlapping teams that can more e ectively execute independently parts of a larger
problem, for the processor to indicate which images have failed during execution and allow continued execution of
the program on the remaining images, for a system of events that can be used for ne grain ordering of execution
segments, and for collective and atomic memory operation subroutines that can provide better performance for
speci c operations involving more than one image.
The facility speci ed in this Technical Speci cation is a compatible extension of Fortran as standardized by
ISO/IEC 1539-1:2010, ISO/IEC 1539-1:2010/Cor 1:2012, and ISO/IEC 1539-1:2010/Cor 2:2013.
It is the intention of ISO/IEC JTC 1/SC22 that the semantics and syntax speci ed by this Technical Speci cation
be included in the next revision of ISO/IEC 1539-1 without change unless experience in the implementation
and use of this feature identi es errors that need to be corrected, or changes are needed to achieve proper
integration, in which case every reasonable e ort will be made to minimize the impact of such changes on existing
implementations.
This Technical Speci cation is organized in 8 clauses:
Scope Clause 1
Normative references Clause 2
Terms and de nitions Clause 3
Compatibility Clause 4
Teams of images Clause 5
Failed images Clause 6
Events Clause 7
Intrinsic procedures Clause 8
Required editorial changes to ISO/IEC 1539-1:2010(E) Clause 9
It also contains the following nonnormative material:
Extended notes Annex A
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1 Scope
This Technical Speci cation speci es the form and establishes the interpretation of facilities that extend the For-
tran language de ned by ISO/IEC 1539-1:2010, ISO/IEC 1539-1:2010/Cor 1:2012, and ISO/IEC 1539-1:2010/Cor
2:2013. The purpose of this Technical Speci cation is to promote portability, reliability, maintainability, and ef-
cient execution of parallel programs written in Fortran, for use on a variety of computing systems.
This Technical Speci cation does not specify formal data consistency model. Developing the formal data consist-
ency model is left until the integration of these facilities into ISO/IEC 1539-1.
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2 Normative references
The following referenced standards are indispensable for the application of this document. For dated references,
only the edition cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
ISO/IEC 1539-1:2010, Information technology|Programming languages|Fortran|Part 1:Base language
ISO/IEC 1539-1:2010/Cor 1:2012, Information technology|Programming languages|Fortran|Part 1:Base lan-
guage TECHNICAL CORRIGENDUM 1
ISO/IEC 1539-1:2010/Cor 2:2013, Information technology|Programming languages|Fortran|Part 1:Base lan-
guage TECHNICAL CORRIGENDUM 2
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3 Terms and de nitions
For the purposes of this document, the terms and de nitions given in ISO/IEC 1539-1:2010 and the following
apply. The intrinsic module ISO FORTRAN ENV is extended by this Technical Speci cation.
3.1
active image
image that has not failed or initiated termination
3.2
asynchronous progress
ability of an image to reference or de ne a coarray on another image without waiting for that image to execute
any particular statement or class of statement
3.3
established coarray
hin a teami coarray that is accessible using a coindexed designator (5.1)
3.4
team
set of images that can readily execute independently of other images (5.1)
3.4.1
current team
hof an imagei team speci ed by the most recently executed CHANGE TEAM statement of an active CHANGE
TEAM construct, or initial team if no CHANGE TEAM construct is active (5.1)
3.4.2
initial team
team, consisting of all images, that began execution of the program (5.1)
3.4.3
parent team
hof a teami current team during the execution of the CHANGE TEAM statement that established the team (5.1)
3.4.4
team number
integer value identifying a team within its parent team (5.1)
3.5
failed image
image that has ceased participating in program execution but has not initiated termination (6.1)
3.6
stopped image
image that has initiated normal termination
3.7
event variable
scalar variable of type EVENT TYPE (7.2) in the intrinsic module ISO FORTRAN ENV
3.8
team variable
scalar variable of type TEAM TYPE (5.2) in the intrinsic module ISO FORTRAN ENV
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4 Compatibility
4.1 New intrinsic procedures
This Technical Speci cation de nes intrinsic procedures in addition to those speci ed in ISO/IEC 1539-1:2010.
Therefore, a Fortran program conforming to ISO/IEC 1539-1:2010 might have a di erent interpretation under
this Technical Speci cation if it invokes an external procedure having the same name as one of the new intrinsic
procedures, unless that procedure is speci ed to have the EXTERNAL attribute.
4.2 Fortran 2008 compatibility
This Technical Speci cation speci es an upwardly compatible extension to ISO/IEC 1539-1:2010, as modi ed by
ISO/IEC 1539-1:2010/Cor 1:2012 and ISO/IEC 1539-1:2010/Cor 2:2013.
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5 Teams of images
5.1 Team concepts
A team of images is a set of images that can readily execute independently of other images. Syntax and semantics
of image-selector (R624 in ISO/IEC 1539-1:2010) are extended to determine how cosubscripts are mapped to
image indices for sibling or ancestor team references. Initially, the current team consists of all images and this is
known as the initial team. Except for the initial team, every team has a unique parent team. A team is divided
into new teams by executing a FORM TEAM statement. Each new team is identi ed by an integer value known
as its team number. Information about the team to which the current image belongs can be determined by the
processor from the collective value of the team variables on the images of the team.
During execution, each image has a current team, which is only changed by execution of CHANGE TEAM and
END TEAM statements. Executing a CHANGE TEAM statement changes the current team to the team speci ed
by the team-variable, and execution of the corresponding END TEAM statement restores the current team back
to that immediately prior to execution of the CHANGE TEAM statement.
A nonallocatable coarray that is neither a dummy argument, host associated with a dummy argument, declared
as a local variable of a subprogram, nor declared in a BLOCK construct is established in the initial team. An
allocated allocatable coarray is established in the team in which it was allocated. An unallocated allocatable
coarray is not established. A coarray that is an associating entity in a coarray-association of a CHANGE TEAM
statement is established in the team of its CHANGE TEAM construct. A nonallocatable coarray that is a
dummy argument or host associated with a dummy argument is established in the team in which the procedure
was invoked. A nonallocatable coarray that is a local variable of a subprogram or host associated with a local
variable of a subprogram is established in the team in which the procedure was invoked. A nonallocatable
coarray declared in a BLOCK construct is established in the team in which the BLOCK statement was executed.
A coarray dummy argument is not established in any ancestor team even if the corresponding actual argument
is established in one or more of them.
5.2 TEAM TYPE
TEAM TYPE is a derived type with private components. It is an extensible type with no type parameters. Each
component is fully default-initialized. A scalar variable of this type describes a team. TEAM TYPE is de ned
in the intrinsic module ISO FORTRAN ENV.
A scalar variable of type TEAM TYPE is a team variable. The default initial value of a team variable shall not
represent any valid team.
5.3 CHANGE TEAM construct
The CHANGE TEAM construct changes the current team to which the executing image belongs.
R501 change-team-construct is change-team-stmt
block
end-change-team-stmt
R502 change-team-stmt is [ team-construct-name: ] CHANGE TEAM ( team-variable
[, coarray-association-list] [, sync-stat-list ] )
R503 coarray-association is codimension-decl => coselector-name
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R504 end-change-team-stmt is END TEAM [ ( sync-stat-list ) ] [ team-construct-name ]
R505 team-variable is scalar-variable
C501 (R501) A branch within a CHANGE TEAM construct shall not have a branch target that is outside the
construct.
C502 (R501) A RETURN statement shall not appear within a CHANGE TEAM construct.
C503 (R501) An exit-stmt or cycle-stmt within a CHANGE TEAM construct shall not belong to an outer
construct.
C504 (R501) If the change-team-stmt of a change-team-construct speci es a team-construct-name, the corres-
ponding end-change-team-stmt shall specify the same team-construct-name. If the change-team-stmt of a
change-team-construct does not specify a team-construct-name, the corresponding end-change-team-stmt
shall not specify a team-construct-name.
C505 (R503) The coarray-name in the codimension-decl shall not be the same as any coselector-name in the
change-team-stmt or the same as a coarray-name in another codimension-decl in the change-team-stmt.
C506 (R505) A team-variable shall be of type TEAM TYPE (5.2).
C507 (R502) No coselector-name shall appear more than once in a change-team-stmt.
C508 (R503) A coselector-name shall be the name of an accessible coarray.
The values of the team-variables on the active images of the team shall be those of team variables de ned by
execution of the same FORM TEAM statement on all active images of the team or be the values of team variables
for the initial team. The current team for the statements of the CHANGE TEAM block is the team speci ed by
the value of the team-variable. The current team is not changed by a rede nition of the team variable during
execution of the CHANGE TEAM construct. A CHANGE TEAM construct completes execution by executing
its END TEAM statement.
A coselector name identi es a coarray. The coarray shall be established when the CHANGE TEAM statement
begins execution. A codimension-decl in a coarray-association associates a coarray with an established coarray
during the execution of the block. This coarray is an associating entity (8.1.3.2, 8.1.3.3, 16.5.1.6 of ISO/IEC
1539-1:2010). Its name is an associate name that has the scope of the construct. It has the declared type,
dynamic type, type parameters, rank, and bounds of the established coarray. Its corank and cobounds are those
speci ed in the codimension-decl.
Within a CHANGE TEAM construct, a coarray that is not an associating entity has the corank and cobounds
that it had when it was established.
An allocatable coarray that was allocated when execution of a CHANGE TEAM construct began shall not be
deallocated during execution of the construct. An allocatable coarray that is allocated when execution of a
CHANGE TEAM construct completes is deallocated if it was not allocated when execution of the construct
began.
The CHANGE TEAM and END TEAM statements are image control statements. All active images of the current
team shall execute the same CHANGE TEAM statement. When a CHANGE TEAM statement is executed, there
is an implicit synchronization of all active images of the team containing the executing image that is identi ed
by team-variable. On each active image of the team, execution of the segment following the statement is delayed
until all other active images of the team have executed the same statement the same number of times since
execution last began in the team that was current before execution of the CHANGE TEAM statement. When a
CHANGE TEAM construct completes execution, there is an implicit synchronization of all active images in the
current team. On each active image of the team, execution of the segment following the END TEAM statement
is delayed until all other active images of the team have executed the same construct the same number of times
since execution last began in the team that was current before execution of the corresponding CHANGE TEAM
c
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ISO/IEC TS 18508:2015(E)
statement.
NOTE 5.1
Deallocation of an allocatable coarray that was not allocated at the beginning of a CHANGE TEAM
construct, but is allocated at the end of execution of the construct, occurs even for allocatable coarrays
with the SAVE attribute.
5.4 Image selectors
The syntax rule R624 image-selector in subclause 6.6 of ISO/IEC 1539-1:2010 is replaced by:
R624 image-selector is lbracket cosubscript-list
[, team-identi er] [, STAT = stat-variable] rbracket
R624a team-identi er is TEAM NUMBER = scalar-int-expr
or TEAM = team-variable
C509 (R624) stat-variable shall not be a coindexed object.
If TEAM= appears in a coarray designator, team-variable shall be de ned with a value that represents the
current or an ancestor team. The coarray shall be established in that team or an ancestor of that team and the
cosubscripts determine the image index in that team.
If TEAM NUMBER = appears in a coarray designator and the current team is not the initial team, the scalar-
int-expr shall be de ned with the value of a team number for one of the teams that were formed by execution of
the FORM TEAM statement for the current team. The coarray shall be established in an ancestor of the current
team and the cosubscripts determine the image index in the team identi ed by TEAM NUMBER. If TEAM -
NUMBER = appears in a coarray designator and the current team is the initial team, the value of scalar-int-expr
is ignored.
Execution of a statement containing an image-selector with a STAT= speci er causes the stat-variable to become
de ned. If the designator is part of an operand that is evaluated, and the object designated is on a failed image,
the stat-variable is de ned with the value STAT FAILED IMAGE in the intrinsic module ISO FORTRAN ENV;
otherwise, it is de ned with the value zero.
The denotation of a stat-variable in an image-selector shall not depend on the evaluation of any entity in the
same statement. The value of an expression shall not depend on the value of any stat-variable that appears in
the same statement. The value of a stat-variable in an image-selector shall not be a ected by the execution of
any part of the statement, other than by whether the image speci ed by the image-selector has failed.
NOTE 5.2
The image selector inb[i] identi es the current team. The image selector inb[i,team_number=1] identi es
a sibling team. The image selector in b[i,TEAM=ancestor] identi es the team ancestor.
NOTE 5.3
The expression x[i,stat=is(f(n))], where is is an array and f(n) is a function that returns an integer
value is an example of the denotation of a stat-variable in an image-selector that depends on the evaluation
of
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