D.16 Multiprocessor Implementation
This subclause allows implementations on multiprocessor platforms to
The following language-defined library package exists:
CPU_Range is range
0 .. implementation-defined
Not_A_Specific_CPU : constant
CPU_Range := 0;
1 .. CPU_Range'Last;
Implementation defined: The value of
CPU_Range'Last in System.Multiprocessors.
A call of Number_Of_CPUs returns the number of processors available to
the program. Within a given partition, each call on Number_Of_CPUs will
return the same value.
For a task type (including the anonymous type of a single_task_declaration
or subprogram, the following language-defined representation aspect may
The aspect CPU is an expression
which shall be of type System.Multiprocessors.CPU_Range.
Aspect Description for CPU: Processor
on which a given task should run.
The CPU aspect shall not be specified on a task interface type.
specified for the CPU aspect of a task type
is evaluated for
the task type is created
The CPU value is then associated with the task object whose task declaration specifies the aspect
The CPU aspect has no effect if it is specified for a subprogram other
than the main subprogram; the CPU value is not associated with any task.
The CPU value is associated with the environment task if the CPU aspect
is specified for the main subprogram. If the CPU aspect is not specified
for the main subprogram it is implementation defined on which processor
the environment task executes.
Implementation defined: The processor
on which the environment task executes in the absence of a value for
the aspect CPU.
The CPU value determines the processor on which the task will activate
and execute; the task is said to be assigned to that processor. If the
CPU value is Not_A_Specific_CPU, then the task is not assigned to a processor.
A task without a CPU aspect specified will activate and execute on the
same processor as its activating task if the activating task is assigned
a processor. If the CPU value is not in the range of System.Multiprocessors.CPU_Range
or is greater than Number_Of_CPUs the task is defined to have failed,
and it becomes a completed task (see 9.2
Extensions to Ada 2005
Wording Changes from Ada 2012
Corrigendum: Clarified when the CPU aspect
expression is evaluated.
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe