D.16 Multiprocessor Implementation
This subclause allows implementations on multiprocessor
platforms to be configured.
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;
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.
If the CPU aspect is specified for a subprogram,
shall be static.
The CPU aspect shall not be specified on a task
specified for the CPU aspect of a task type is evaluated each time an
object of the task type is created (see 9.1
The CPU value is then associated with the task object.
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.
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
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