ICV Initialization

| OPENMP API Specification: Version 5.0 November 2018

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2.5.2 ICV Initialization

Table 2.1:

ICV Initial Values


ICV	Environment Variable	Initial value




dyn-var	OMP_DYNAMIC	See description below
nthreads-var	OMP_NUM_THREADS	Implementation defined
run-sched-var	OMP_SCHEDULE	Implementation defined
def-sched-var	(none)	Implementation defined
bind-var	OMP_PROC_BIND	Implementation defined
stacksize-var	OMP_STACKSIZE	Implementation defined
wait-policy-var	OMP_WAIT_POLICY	Implementation defined
thread-limit-var	OMP_THREAD_LIMIT	Implementation defined
max-active-levels-var	OMP_MAX_ACTIVE_LEVELS, OMP_NESTED	See description below
active-levels-var	(none)	zero
levels-var	(none)	zero
place-partition-var	OMP_PLACES	Implementation defined
cancel-var	OMP_CANCELLATION	false
display-affinity-var	OMP_DISPLAY_AFFINITY	false
affinity-format-var	OMP_AFFINITY_FORMAT	Implementation defined
default-device-var	OMP_DEFAULT_DEVICE	Implementation defined
target-offload-var	OMP_TARGET_OFFLOAD	DEFAULT
max-task-priority-var	OMP_MAX_TASK_PRIORITY	zero
tool-var	OMP_TOOL	enabled
tool-libraries-var	OMP_TOOL_LIBRARIES	empty string
debug-var	OMP_DEBUG	disabled
def-allocator-var	OMP_ALLOCATOR	Implementation defined

Table 2.1 shows the ICVs, associated environment variables, and initial values.

Description

Each device has its own ICVs.
The initial value of dyn-var is implementation defined if the implementation supports dynamic adjustment of the number of threads; otherwise, the initial value is false.
The value of the nthreads-var ICV is a list.
The value of the bind-var ICV is a list.
The initial value of max-active-levels-var is the number of active levels of parallelism that the implementation supports if OMP_NUM_THREADS or OMP_PROC_BIND is set to a comma-separated list of more than one value. Otherwise, the initial value of max-active-levels-var is implementation defined.

The host and target device ICVs are initialized before any OpenMP API construct or OpenMP API routine executes. After the initial values are assigned, the values of any OpenMP environment variables that were set by the user are read and the associated ICVs for the host device are modified accordingly. The method for initializing a target device’s ICVs is implementation defined.

Cross References

OMP_SCHEDULE environment variable, see Section 6.1 on page 1646.
OMP_NUM_THREADS environment variable, see Section 6.2 on page 1650.
OMP_DYNAMIC environment variable, see Section 6.3 on page 1652.
OMP_PROC_BIND environment variable, see Section 6.4 on page 1653.
OMP_PLACES environment variable, see Section 6.5 on page 1655.
OMP_STACKSIZE environment variable, see Section 6.6 on page 1659.
OMP_WAIT_POLICY environment variable, see Section 6.7 on page 1662.
OMP_MAX_ACTIVE_LEVELS environment variable, see Section 6.8 on page 1664.
OMP_NESTED environment variable, see Section 6.9 on page 1665.
OMP_THREAD_LIMIT environment variable, see Section 6.10 on page 1667.
OMP_CANCELLATION environment variable, see Section 6.11 on page 1668.
OMP_DISPLAY_AFFINITY environment variable, see Section 6.13 on page 1671.
OMP_AFFINITY_FORMAT environment variable, see Section 6.14 on page 1674.
OMP_DEFAULT_DEVICE environment variable, see Section 6.15 on page 1677.
OMP_MAX_TASK_PRIORITY environment variable, see Section 6.16 on page 1678.
OMP_TARGET_OFFLOAD environment variable, see Section 6.17 on page 1680.
OMP_TOOL environment variable, see Section 6.18 on page 1681.
OMP_TOOL_LIBRARIES environment variable, see Section 6.19 on page 1682.
OMP_DEBUG environment variable, see Section 6.20 on page 1684.
OMP_ALLOCATOR environment variable, see Section 6.21 on page 1686.

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