# Supported Environment Variables

You can customize your system environment by specifying paths where the compiler searches for certain files such as libraries, include files, configuration files, and certain settings.

## Compiler Compile-Time Environment Variables

The following table shows the compile-time environment variables that affect the compiler:

Compile-Time Environment Variable | Description
--- | ---
CL (Windows) _CL_ (Windows) | Define the files and options you use most often with the CL variable. Note: You cannot set the CL environment variable to a string that contains an equal sign. You can use the pound sign instead. In the following example, the pound sign (#) is used as a substitute for an equal sign in the assigned string: `SET CL=/Dtest#100`
COV_DIR (Windows) | Same as PROF_DIR.
COV_DPI (Windows) | Same as PROF_DPI.
IA32ROOT (IA-32 architecture and Intel® 64 architecture) | Points to the directories containing the include and library files for a non-standard installation structure. ### Note IA-32 architecture is no longer supported on macOS*.
ICCCFG | Specifies the configuration file for customizing compilations when invoking the compiler using icc. Used instead of the default configuration file.
ICPCCFG | Specifies the configuration file for customizing compilations when invoking the compiler using icpc. Used instead of the default configuration file.
ICLCFG (Windows) | Specifies a configuration file, which the compiler should use instead of the default configuration file.
INTEL_LICENSE_FILE | Specifies the location for the Intel license file. ### Note On Windows, this environment variable cannot be set from Visual Studio.
__INTEL_PRE_CFLAGS __INTEL_POST_CFLAGS | Specifies a set of compiler options to add to the compile line. This is an extension to the facility already provided in the compiler configuration file icl.cfg. ### Note By default, a configuration file named icl.cfg (Windows), icc.cfg (Linux, macOS), or icpc.cfg (Linux, macOS) is used. This file is in the same directory as the compiler executable. To use another configuration file in another location, you can use the `ICLCFG` (Windows), `ICCCFG` (Linux, macOS), or `ICPCCFG` (Linux, macOS) environment variable to assign the directory and file name for the configuration file. You can insert command line options in the prefix position using `__INTEL_PRE_CFLAGS` or in the suffix position using `__INTEL_POST_CFLAGS`. The command line is built as follows: Syntax: (On Windows, use icl. On Linux or macOS, use icc) `icl/icc``<PRE flags> <flags from configuration file> <flags from the compiler invocation> <POST flags>` ### Note The driver issues a warning that the compiler is overriding an option because of an environment variable, but only when you include the option /W5 (Windows) or -w3 (Linux and macOS).
INTEL_TARGET_ARCH_IA32 (Linux and Windows) | Set this environment variable to target 32-bit compilations for all associated tools (this includes the compiler and Intel-specific linker tools). Without this environment variable, you will be required to use the explicit command line options, /Qm32 on Windows and -m32 on Linux, for each compiler invocation. ### Note IA-32 architecture is no longer supported on macOS. IA-32 is deprecated for other operating systems and will be removed in a future release.
PATH | Specifies the directories the system searches for binary executable files. ### Note On Windows, this also affects the search for Dynamic Link Libraries (DLLs).
TMP TMPDIR TEMP | Specifies the location for temporary files. If none of these are specified, or writeable, or found, the compiler stores temporary files in /tmp (Linux, macOS) or the current directory (Windows). The compiler searches for these variables in the following order: TMP, TMPDIR, and TEMP. ### Note On Windows, these environment variables cannot be set from Visual Studio.
LD_LIBRARY_PATH (Linux) | Specifies the location for shared objects (.so files).
DYLD_LIBRARY_PATH (macOS) | Specifies the path for dynamic libraries.
INCLUDE (Windows) | Specifies the directories for the source header files (include files).
LIB (Windows) | Specifies the directories for all libraries used by the compiler and linker.
GNU Environment Variables and Extensions
CPATH (Linux and macOS) | Specifies the path to include directory for C/C++ compilations.
C_INCLUDE_PATH (Linux and macOS) | Specifies path to include directory for C compilations.
CPLUS_INCLUDE_PATH (Linux and macOS) | Specifies path to include directory for C++ compilations.
DEPENDENCIES_OUTPUT (Linux and macOS) | Specifies how to output dependencies for make based on the non-system header files processed by the compiler. System header files are ignored in the dependency output.
GCC_EXEC_PREFIX (Linux) | Specifies alternative names for the linker (ld) and assembler (as).
GCCROOT (Linux) | Specifies the location of the GCC* binaries. Set this variable only when the compiler cannot locate the GCC binaries when using the -gcc-name option.
GXX_INCLUDE (Linux) | Specifies the location of the GCC headers. Set this variable to specify the locations of the GCC installed files when the compiler does not find the needed values as specified by the use of `-gcc-name=directory-name/gcc` or `-gxx-name=directory-name/g++`.
GXX_ROOT (Linux) | Specifies the location of the GCC binaries. Set this variable to specify the locations of the GCC installed files when the compiler does not find the needed values as specified by the use of `-gcc-name=directory-name/gcc` or `-gxx-name=directory-name/g++`.
LIBRARY_PATH (Linux and macOS) | Specifies the path for libraries to be used during the link phase.
SUNPRO_DEPENDENCIES (Linux) | This variable is the same as DEPENDENCIES_OUTPUT, except that system header files are not ignored.

### Note

INTEL_ROOT is an environment variable that is reserved for the Intel® Compiler. Its use is not supported.

## Compiler Run-Time Environment Variables

The following table summarizes compiler environment variables that are recognized at run time.

Run-Time Environment Variable | Description
--- | ---
INTEL_CHKP_REPORT_MODE (Linux) | Changes the pointer checker reporting mode at run time. See Finding and Reporting Out-of-Bounds Errors.
INTEL_ISA_DISABLE | Causes named features (in a comma-separated list) not to be visible on the host even if the CPUID reports that it has them onboard. See CPU Feature Targeting.
GNU extensions (recognized by the Intel OpenMP* compatibility library)
GOMP_CPU_AFFINITY (Linux) | GNU extension recognized by the Intel OpenMP compatibility library. Specifies a list of OS processor IDs. You must set this environment variable before the first parallel region or before certain API calls including `omp_get_max_threads()`, `omp_get_num_procs()` and any affinity API calls. For detailed information on this environment variable, see Thread Affinity Interface. Default: Affinity is disabled
GOMP_STACKSIZE (Linux) | GNU extension recognized by the Intel OpenMP compatibility library. Same as OMP_STACKSIZE.KMP_STACKSIZE overrides GOMP_STACKSIZE, which overrides OMP_STACKSIZE. Default: See the description for OMP_STACKSIZE.
OpenMP Environment Variables (OMP_) and Extensions (KMP_)
OMP_CANCELLATION | Activates cancellation of the innermost enclosing region of the type specified. If set to TRUE, the effects of the cancel construct and of cancellation points are enabled and cancellation is activated. If set to FALSE, cancellation is disabled and the cancel construct and cancellation points are effectively ignored. ### Note Internal barrier code will work differently depending on whether the cancellation is enabled. Barrier code should repeatedly check the global flag to figure out if the cancellation had been triggered. If a thread observes the cancellation it should leave the barrier prematurely with the return value 1 (may wake up other threads). Otherwise, it should leave the barrier with the return value 0. Enables (TRUE) or disables (FALSE) cancellation of the innermost enclosing region of the type specified. Default: FALSE Example: `OMP_CANCELLATION=TRUE`
OMP_DISPLAY_ENV | Enables (TRUE) or disables (FALSE) the printing to stderr of the OpenMP version number and the values associated with the OpenMP environment variable. Possible values are: TRUE, FALSE, or VERBOSE. Default: FALSE Example:`OMP_DISPLAY_ENV=TRUE`
OMP_DEFAULT_DEVICE | Sets the device that will be used in a target region. The OpenMP routine omp_set_default_device or a device clause in a target pragma can override this variable. If no device with the specified device number exists, the code is executed on the host. If this environment variable is not set, device number 0 is used.
OMP_DYNAMIC | Enables (TRUE) or disables (FALSE) the dynamic adjustment of the number of threads. Default: FALSE Example:`OMP_DYNAMIC=TRUE`
OMP_MAX_ACTIVE_LEVELS | The maximum number of levels of parallel nesting for the program. Possible values: Non-negative integer. Default: 1
OMP_NESTED | Deprecated; use OMP_MAX_ACTIVE_LEVELS instead.
OMP_NUM_THREADS | Sets the maximum number of threads to use for OpenMP parallel regions if no other value is specified in the application. The value can be a single integer, in which case it specifies the number of threads for all parallel regions. The value can also be a comma-separated list of integers, in which case each integer specifies the number of threads for a parallel region at a nesting level. The first position in the list represents the outer-most parallel nesting level, the second position represents the next-inner parallel nesting level, and so on. At any level, the integer can be left out of the list. If the first integer in a list is left out, it implies the normal default value for threads is used at the outer-most level. If the integer is left out of any other level, the number of threads for that level is inherited from the previous level. This environment variable applies to the options Qopenmp (Windows) or qopenmp (Linux and macOS), and Qparallel (Windows) or parallel (Linux and macOS. Default: The number of processors visible to the operating system on which the program is executed. Syntax:`OMP_NUM_THREADS=value[,value]*`
OMP_PLACES | Specifies an explicit ordered list of places, either as an abstract name describing a set of places or as an explicit list of places described by nonnegative numbers. An exclusion operator “!” can also be used to exclude the number or place immediately following the operator. For explicit lists, the meaning of the numbers and how the numbering is done for a list of nonnegative numbers are implementation defined. Generally, the numbers represent the smallest unit of execution exposed by the execution environment, typically a hardware thread. Intervals can be specified using the `<lower-bound>` : `<length>` : `<stride>` notation to represent the following list of numbers:
    "<lower-bound>, <lower-bound> + <stride>, ...,
    <lower-bound> +(<length>-1)*<stride>."
When `<stride>` is omitted, a unit stride is assumed. Intervals can specify numbers within a place as well as sequences of places.
    # EXPLICIT LIST EXAMPLE
    setenv OMP_PLACES "{0,1,2,3},{4,5,6,7},{8,9,10,11},{12,13,14,15}"
    setenv OMP_PLACES "{0:4},{4:4},{8:4},{12:4}"
    setenv OMP_PLACES "{0:4}:4:4"
The abstract names listed below should be understood by the execution and run-time environment: `threads`: Each place corresponds to a single hardware thread on the target machine. `cores`: Each place corresponds to a single core (having one or more hardware threads) on the target machine. `ll_caches`: Each place corresponds to a set of cores that share the last level cache on the device. `numa_domains`: Each place corresponds to a set of cores for which their closest memory on the device is 1) the same memory and 2) at a similar distance from the cores. `sockets`: Each place corresponds to a single socket (consisting of one or more cores) on the target machine. When requesting fewer places or more resources than available on the system, the determination of which resources of type `abstract_name` are to be included in the place list is implementation-defined. The precise definitions of the abstract names are implementation defined. An implementation may also add abstract names as appropriate for the target platform. The abstract name may be appended by a positive number in parentheses to denote the length of the place list to be created, that is `abstract_name(num-places)`.
    # ABSTRACT NAMES EXAMPLE
      setenv OMP_PLACES threads
      setenv OMP_PLACES threads(4)
### Note If any numerical values cannot be mapped to a processor on the target platform the behavior is implementation-defined. The behavior is also implementation-defined when the OMP_PLACES environment variable is defined using an abstract name.
OMP_PROC_BIND (Windows, Linux) | Sets the thread affinity policy to be used for parallel regions at the corresponding nested level. Enables (TRUE) or disables (FALSE) the binding of threads to processor contexts. If enabled, this is the same as specifying KMP_AFFINITY=scatter. If disabled, this is the same as specifying KMP_AFFINITY=none. Acceptable values: TRUE, FALSE, or a comma separated list, each element of which is one of the following values: PRIMARY, MASTER (deprecated), CLOSE, SPREAD. Default: FALSE If set to FALSE, the execution environment may move OpenMP threads between OpenMP places, thread affinity is disabled, and proc_bind clauses on parallel constructs are ignored. Otherwise, the execution environment should not move OpenMP threads between OpenMP places, thread affinity is enabled, and the initial thread is bound to the first place in the OpenMP place list. If set to PRIMARY, all threads are bound to the same place as the primary thread. If set to CLOSE, threads are bound to successive places, close to where the primary thread is bound. If set to SPREAD, the primary thread's partition is subdivided and threads are bound to single place successive sub-partitions. ### Note KMP_AFFINITY takes precedence over GOMP_CPU_AFFINITY and OMP_PROC_BIND. GOMP_CPU_AFFINITY takes precedence over OMP_PROC_BIND.
OMP_SCHEDULE | Sets the run-time schedule type and an optional chunk size. Default: static, no chunk size specified Example syntax:`OMP_SCHEDULE="[modifier:]kind[,chunk_size]"` where `modifier` is one of monotonic or nonmonotonic `kind` is one of static, dynamic, guided, or auto `chunk_size` is a positive integer ### Note Some environment variables are available for both Intel® microprocessors and non-Intel microprocessors, but may perform additional optimizations for Intel® microprocessors than for non-Intel microprocessors.
OMP_STACKSIZE | Sets the number of bytes to allocate for each OpenMP thread to use as the private stack for the thread. Recommended size is 16M. Use the optional suffixes to specify byte units: B (bytes), K (Kilobytes), M (Megabytes), G (Gigabytes), or T (Terabytes) to specify the units. If you specify a value without a suffix, the byte unit is assumed to be K (Kilobytes). This variable does not affect the native operating system threads created by the user program, or the thread executing the sequential part of an OpenMP program or parallel programs created using the option Qparallel (Windows) or parallel (Linux and macOS) . The kmp_{set,get}_stacksize_s() routines set/retrieve the value. The kmp_set_stacksize_s() routine must be called from sequential part, before first parallel region is created. Otherwise, calling kmp_set_stacksize_s() has no effect. Default (IA-32 architecture): 2M Default (Intel® 64 architecture): 4M ### Note IA-32 architecture is no longer supported on macOS. IA-32 is deprecated for other operating systems and will be removed in a future release. Related environment variables: KMP_STACKSIZE (overrides OMP_STACKSIZE). Syntax:`OMP_STACKSIZE=value`
OMP_THREAD_LIMIT | Limits the number of simultaneously-executing threads in an OpenMP program. If this limit is reached and another native operating system thread encounters OpenMP API calls or constructs, the program can abort with an error message. If this limit is reached when an OpenMP parallel region begins, a one-time warning message might be generated indicating that the number of threads in the team was reduced, but the program will continue. This environment variable is only used for programs compiled with the following options: Qopenmp (Windows) or qopenmp (Linux and macOS), or Qparallel (Windows) or parallel (Linux and macOS) . The omp_get_thread_limit() routine returns the value of the limit. Default: No enforced limit Related environment variable: KMP_ALL_THREADS (overrides OMP_THREAD_LIMIT). Example syntax:`OMP_THREAD_LIMIT=value`
OMP_WAIT_POLICY | Decides whether threads spin (active) or yield (passive) while they are waiting. `OMP_WAIT_POLICY=ACTIVE` is an alias for `KMP_LIBRARY=turnaround`, and `OMP_WAIT_POLICY=PASSIVE` is an alias for `KMP_LIBRARY=throughput`. Default: Passive Syntax:`OMP_WAIT_POLICY=value`
OMP_DISPLAY_AFFINITY | Instructs the runtime to display formatted affinity information for all OpenMP threads in the parallel region upon entering the first parallel region and when any change occurs in the information accessible by the format specifiers listed in the OMP_AFFINITY_FORMAT entry. Possible values: TRUE or FALSE Default: FALSE
OMP_AFFINITY_FORMAT | Defines the format when displaying OpenMP thread affinity information. Possible values are any string with the following format field available: `%t` or `%{team_num}`: Value returned by `omp_get_team_num()` `%T` or `%{num_teams}`: Value returned by `omp_get_num_teams()` `%L` or `%{nesting_level}`: Value returned by `omp_get_level()` `%n` or `%{thread_num}`: Value returned by `omp_get_thread_num()` `%a` or `%{ancestor_tnum}`: Value returned by `omp_get_ancestor_thread_num(omp_get_level() – 1)` `%H` or `%{host}`: Name of host device `%P` or `%{process_id}`: Process ID `%i` or `%{native_thread_id}`: Native thread ID on the platform `%A` or `%{thread_affinity}`: List of processor ID on which a thread may execute Default: '`OMP: pid %P tid %i thread %n bound to OS proc set {%A}`'
OMP_MAX_TASK_PRIORITY | Controls the use of task priorities by setting the initial value. Possible values: Non-negative integer. Default: `0`
OMP_TOOL | Controls whether the OpenMP runtime will try to register a first party tool that uses OMPT interface. Possible values: ENABLED or DISABLED. Default: ENABLED ### Note Only the host OpenMP runtime is supported.
OMP_TOOL_LIBRARIES | Sets a list of first-party tool locations that use the OMPT interface. The list enumerates names of dynamically-loadable libraries with OS-specific path separator. Default: Empty ### Note Only the host OpenMP runtime is supported.
OMP_TOOL_VERBOSE_INIT | Controls whether the OpenMP runtime will verbosely log the registration of a tool that uses the OMPT interface. Possible values: DISABLED: Do not log the registration. STDOUT: Log the registration to stdout. STDERR: Log the registration to stderr. File_Name: Log the registration to the location specified by File_Name. Default:DISABLED ### Note Only the host OpenMP runtime is supported.
OMP_DEBUG | Controls whether the OpenMP runtime collects information that an OMPD library may need to support a tool. Possible values: ENABLED or DISABLED. Default: DISABLED ### Note Only the host OpenMP runtime is supported.
OMP_ALLOCATOR | Specifies the default allocator for allocation calls, directives, and clauses that do not specify an allocator. Default: `omp_default_mem_alloc` Syntax: `<PredefinedMemAllocator> | <PredefinedMemSpace> | <PredefinedMemSpace>:<Traits>` Currently supported values for <PredefinedMemAllocator> and <PredefinedMemSpace> : `omp_default_mem_alloc` and `omp_default_mem_space` Additional values are supported if `libmemkind` is available and there is system support for it: `omp_high_bw_mem_alloc` and `omp_high_bw_mem_space` `omp_large_cap_mem_alloc` and `omp_large_cap_mem_space` Refer to the OpenMP specification for more information.
OMP_NUM_TEAMS | Sets the maximum number of teams created by a teams construct by setting nteams-var ICV. Possible values: Positive integer. Default: 1
OMP_TEAMS_THREAD_LIMIT | Sets the maximum number of OpenMP threads to use in each team created by a teams construct. Possible values: Positive integer. Default: <NumberOfProcessors> / <nteams-var ICV>
KMP_AFFINITY (Linux, Windows) | Enables run-time library to bind threads to physical processing units. You must set this environment variable before the first parallel region, or certain API calls including `omp_get_max_threads()`, `omp_get_num_procs()` and any affinity API calls. For detailed information on this environment variable, see Thread Affinity Interface. Default: noverbose,warnings,noreset,respect,granularity=core,none Default (Windows with multiple processor groups): noverbose,warnings,noreset,norespect,granularity=group,compact,0,0 ### Note On Windows with multiple processor groups, the norespect affinity modifier is assumed when the process affinity mask equals a single processor group (which is default on Windows). Otherwise, the respect affinity modifier is used.
KMP_ALL_THREADS | Limits the number of simultaneously-executing threads in an OpenMP program. If this limit is reached and another native operating system thread encounters OpenMP API calls or constructs, then the program may abort with an error message. If this limit is reached at the time an OpenMP parallel region begins, a one-time warning message may be generated indicating that the number of threads in the team was reduced, but the program will continue execution. This environment variable is only used for programs compiled with the Qopenmp(Windows) or qopenmp (Linux and macOS) option. Default: No enforced limit.
KMP_BLOCKTIME | Sets the time, in milliseconds, that a thread should wait, after completing the execution of a parallel region, before sleeping. Use the optional character suffixes: s (seconds), m (minutes), h (hours), or d (days) to specify the units. Specify infinite for an unlimited wait time. Default: 200 milliseconds Related Environment Variable: KMP_LIBRARY environment variable.
KMP_CPUINFO_FILE | Specifies an alternate file name for a file containing the machine topology description. The file must be in the same format as /proc/cpuinfo. Default: None
KMP_DETERMINISTIC_REDUCTION | Enables (TRUE) or disables (FALSE) the use of a specific ordering of the reduction operations for implementing the reduction clause for an OpenMP parallel region. This has the effect that, for a given number of threads, in a given parallel region, for a given data set and reduction operation, a floating point reduction done for an OpenMP reduction clause has a consistent floating point result from run to run, since round-off errors are identical. ### Note When compiling, you must set the following flag to ensure correct behavior: `-fp-model precise` (Linux) `-fp:precise` (Windows) Default: FALSE
KMP_DYNAMIC_MODE | Selects the method used to determine the number of threads to use for a parallel region when `OMP_DYNAMIC=TRUE`. Possible values: (asat | load_balance | thread_limit), where, asat: estimates number of threads based on parallel start time; ### Note Support for asat (automatic self-allocating threads) is now deprecated and will be removed in a future release. load_balance: tries to avoid using more threads than available execution units on the machine; thread_limit: tries to avoid using more threads than total execution units on the machine. Default (IA-32 architecture): load_balance (on all supported OSes) Default (Intel® 64 architecture): load_balance (on all supported OSes) ### Note IA-32 architecture is no longer supported on macOS. IA-32 is deprecated for other operating systems and will be removed in a future release.
KMP_HOT_TEAMS_MAX_LEVEL | Sets the maximum nested level to which teams of threads will be hot. ### Note A hot team is a team of threads optimized for faster reuse by subsequent parallel regions. In a hot team, threads are kept ready for execution of the next parallel region, in contrast to the cold team, which is freed after each parallel region, with its threads going into a common pool of threads. For values of 2 and above, nested parallelism should be enabled. Default: 1
KMP_HOT_TEAMS_MODE | Specifies the run-time behavior when the number of threads in a hot team is reduced. Possible values: 0: Extra threads are freed and put into a common pool of threads. 1: Extra threads are kept in the team in reserve, for faster reuse in subsequent parallel regions. Default: 0
KMP_HW_SUBSET | Specifies the subset of available hardware resources for the hardware topology hierarchy. The subset is specified in terms of number of units per upper layer unit starting from top layer downwards. For example, it can specify the number of sockets (top layer units), cores per socket, and the threads per core, to use with an OpenMP application. It is a convenient alternative to writing complicated explicit affinity settings or a limiting process affinity mask. You can also specify an offset value to set which resources to use. When available, you can specify attributes to select different subsets of resources. An extended syntax is available when `KMP_TOPOLOGY_METHOD=hwloc`. Depending on what resources are detected, you may be able to specify additional resources, such as NUMA nodes and groups of hardware resources that share certain cache levels. Basic syntax: `[num_units]ID[@offset][:attribute] [,[num_units]ID[@offset][:attribute]...]` where `num_units` is either a positive integer, which requests an exact number of resources, or an asterisk (*), which means using all available resources at that layer (for example, using all cores per socket). If `num_units` is not specified, the asterisk (*) semantics are assumed. `ID` is a supported ID: S - socket num_units specifies the requested number of sockets. D - die num_units specifies the requested number of dies per socket. C - core num_units specifies the requested number of cores per die - if any - otherwise, per socket. T - thread num_units specifies the requested number of HW threads per core. Supported unit IDs are not case-sensitive. `offset` is the number of units to skip (optional). `attribute` is an attribute differentiating resources at a particular layer (optional). This is only available for the core layer on machines with Intel® Hybrid Technology. The attributes available to users are: Core type: Either intel_atom or intel_core Core efficiency: Specified as `effnum` where num is a number from 0 to the number of core efficiencies detected in the machine topology minus one. For example: `eff0`. The greater the efficiency number, the more performant the core. There may be more core efficiencies than core types, which can be viewed by setting `KMP_AFFINITY=verbose`. ### Note The hardware cache can be specified as a unit, for example L2 for L2 cache, or LL for last level cache. Extended syntax when `KMP_TOPOLOGY_METHOD=hwloc`: Additional IDs can be specified if detected. For example: N - numa num_units specifies the requested number of NUMA nodes per upper layer unit, e.g. per socket. TI - tile num_units specifies the requested number of tiles to use per upper layer unit, e.g. per NUMA node. When any numa or tile units are specified in KMP_HW_SUBSET, the KMP_TOPOLOGY_METHOD will be automatically set to hwloc,so there is no need to set it explicitly. If you don't specify one or more types of resource, such as socket or thread, all available resources of that type are used. The run-time library prints a warning, and the setting of KMP_HW_SUBSET is ignored if: a resource is specified, but detection of that resource is not supported by the chosen topology detection method and/or a resource is specified twice. An exception to this condition is if attributes differentiate the resource. attributes are used when unavailable, not detected in the machine topology, or conflict with each other. This variable does not work if the OpenMP affinity is set to `disabled`. Default: If omitted, the default value is to use all the available hardware resources. Examples: `2s,4c,2t`: Use the first 2 sockets (s0 and s1), the first 4 cores on each socket (c0 - c3), and 2 threads per core. `2s@2,4c@8,2t`: Skip the first 2 sockets (s0 and s1) and use 2 sockets (s2-s3), skip the first 8 cores (c0-c7) and use 4 cores on each socket (c8-c11), and use 2 threads per core. `5C@1,3T`: Use all available sockets, skip the first core and use 5 cores, and use 3 threads per core. `1T`: Use all cores on all sockets, 1 thread per core. `1s, 1d, 1n, 1c, 1t`: Use 1 socket, 1 die, 1 NUMA node, 1 core, 1 thread - use HW thread as a result. `4c:intel_atom,5c:intel_core`: Use all available sockets and use 4 Intel Atom® processor cores and 5 Intel® Core™ processor cores per socket. `2c:eff0,3c:eff1`: Use all available sockets and use 2 cores with efficiency 0 and 3 cores with efficiency 1 per socket. `1s, 1c, 1t`: Use 1 socket, 1 core, 1 thread. This may result in using single thread on a 3-layer topology architecture, or multiple threads on 4-layer or 5-layer architecture. Result may even be different on the same architecture, depending on KMP_TOPOLOGY_METHOD specified, as hwloc can often detect more topology layers than default method used by the OpenMP run-time library. To see the result of the setting, you can specify the verbose modifier in for the KMP_AFFINITY environment variable. The OpenMP run-time library will output to stderr stream the information about discovered HW topology before and after the KMP_HW_SUBSET setting was applied. For example, on Intel® Xeon Phi™ 7210 CPU in SNC-4 Clustering Mode, the setting KMP_AFFINITY=verbose KMP_HW_SUBSET=1N,1L2,1L1,1T outputs various verbose information to stderr, including the following lines about discovered HW topology before and after KMP_HW_SUBSET was applied: Info #191: KMP_AFFINITY: 1 socket x 4 NUMA domains/socket x 8 tiles/NUMA domain x 2 cores/tile x 4 threads/core. (64 total cores) Info #191: KMP_HW_SUBSET 1 socket x 1 NUMA domain/socket x 1 tile/NUMA domain x 1 core/tile x 1 thread/core (1 total cores)
KMP_INHERIT_FP_CONTROL | Enables (TRUE) or disables (FALSE) the copying of the floating-point control settings of the primary thread to the floating-point control settings of the OpenMP worker threads at the start of each parallel region. Default: TRUE
KMP_LIBRARY | Selects the OpenMP run-time library execution mode. The values for this variable are serial, turnaround, or throughput. Default: throughput
KMP_PLACE_THREADS | Deprecated; use KMP_HW_SUBSET instead.
KMP_SETTINGS | Enables (TRUE) or disables (FALSE) the printing of OpenMP run-time library environment variables during program execution. Two lists of variables are printed: user-defined environment variables settings and effective values of variables used by OpenMP run-time library. Default: FALSE
KMP_STACKSIZE | Sets the number of bytes to allocate for each OpenMP thread to use as its private stack. Recommended size is 16m. Use the optional suffixes to specify byte units: B (bytes), K (Kilobytes), M (Megabytes), G (Gigabytes), or T (Terabytes) to specify the units. If you specify a value without a suffix, the byte unit is assumed to be K (Kilobytes). This variable does not affect the native operating system threads created by the user program nor the thread executing the sequential part of an OpenMP program or parallel programs created using the option Qparallel (Windows) or parallel (Linux and macOS) . KMP_STACKSIZE overrides GOMP_STACKSIZE, which overrides OMP_STACKSIZE.Default (IA-32 architecture): 2m Default (Intel® 64 architecture): 4m ### Note IA-32 architecture is no longer supported on macOS. IA-32 is deprecated for other operating systems and will be removed in a future release.
KMP_TOPOLOGY_METHOD | Forces OpenMP to use a particular machine topology modeling method. Possible values are: all: Lets OpenMP choose which topology method is most appropriate based on the platform and possibly other environment variable settings. cpuid_leaf11: Decodes the APIC identifiers as specified by leaf 11 of the cpuid instruction. cpuid_leaf4: Decodes the APIC identifiers as specified in leaf 4 of the cpuid instruction. cpuinfo: If `KMP_CPUINFO_FILE` is not specified, forces OpenMP to parse /proc/cpuinfo to determine the topology (Linux only). If `KMP_CPUINFO_FILE` is specified as described above, uses it (Windows or Linux). group: Models the machine as a 2-level map, with level 0 specifying the different processors in a group, and level 1 specifying the different groups (Windows 64-bit only) . ### Note Support for group is now deprecated and will be removed in a future release. Use all instead. flat: Models the machine as a flat (linear) list of processors. hwloc: Models the machine as the Portable Hardware Locality* (hwloc) library does. This model is the most detailed and includes, but is not limited to: numa nodes, packages, cores, hardware threads, caches, and Windows processor groups. Default: all
KMP_USER_LEVEL_MWAIT | Enables (TRUE) or disables (FALSE) the use of user-level mwait as alternative to putting waiting threads to sleep, if available, either from ring3 or WAITPKG. Default: FALSE
KMP_VERSION | Enables (TRUE) or disables (FALSE) the printing of OpenMP run-time library version information during program execution. Default: FALSE
KMP_WARNINGS | Enables (TRUE) or disables (FALSE) displaying warnings from the OpenMP run-time library during program execution. Default: TRUE
Profile Guided Optimization (PGO_) Environment Variables
INTEL_PROF_DUMP_CUMULATIVE | When using interval profile dumping (initiated by INTEL_PROF_DUMP_INTERVAL or the function _PGOPTI_Set_Interval_Prof_Dump) during the execution of an instrumented user application, allows creation of a single .dyn file to contain profiling information instead of multiple .dyn files. If not set, executing an instrumented user application creates a new .dyn file for each interval. Setting this environment variable is useful for applications that do not terminate or those that terminate abnormally (bypass the normal exit code).
INTEL_PROF_DUMP_INTERVAL | Initiates interval profile dumping in an instrumented user application. This environment variable may be used to initiate Interval Profile Dumping in an instrumented application. See Interval Profile Dumping for more information
INTEL_PROF_DYN_PREFIX | Specifies the prefix to be used for the .dyn filename to distinguish it from the other .dyn files dumped by other PGO runs. Executing the instrumented application generates a .dyn filename as follows: <prefix>_<timestamp>_<pid>.dyn, where `<prefix>` is the identifier that you have specified. ### Note The value specified in this environment variable must not contain < > : " / \ | ? * characters. The default naming scheme is used if an invalid prefix is specified.
PROF_DIR | Specifies the directory where profiling files (files with extensions .dyn, .dpi, .spi and so on) are stored. The default is to store the .dyn files in the source directory of the file containing the first executed instrumented routine in the binary compiled with [Q]prof-gen option. This variable applies to all three phases of the profiling process: Instrumentation compilation and linking Instrumented execution Feedback compilation
PROF_DPI | Name for the .dpi file. Default: pgopti.dpi
PROF_DUMP_INTERVAL | Deprecated; use INTEL_PROF_DUMP_INTERVAL instead.
PROF_NO_CLOBBER | Alters the feedback compilation phase slightly. By default, during the feedback compilation phase, the compiler merges data from all dynamic information files and creates a new pgopti.dpi file if the .dyn files are newer than an existing pgopti.dpi file. When this variable is set, the compiler does not overwrite the existing pgopti.dpi file. Instead, the compiler issues a warning. You must remove the pgopti.dpi file if you want to use additional dynamic information files.

The following table summarizes CPU environment variables that are recognized at run time.

Runtime configuration | Default value | Description
--- | --- | ---
CL_CONFIG_CPU_FORCE_PRIVATE_MEM_SIZE | 32KB | Forces CL_DEVICE_PRIVATE_MEM_SIZE for the CPU device to be the given value. The value must include the unit; for example: 8MB, 8192KB, 8388608B. ### Note You must compile your host application with sufficient stack size.
CL_CONFIG_CPU_FORCE_LOCAL_MEM_SIZE | 32KB | Forces CL_DEVICE_LOCAL_MEM_SIZE for CPU device to be the given value. The value needs to be set with size including units, examples: 8MB, 8192KB, 8388608B. ### Note You must compile your host application with sufficient stack size. Our recommendation is to set the stack size equal to twice the local memory size to cover possible application and OpenCL Runtime overheads.
CL_CONFIG_CPU_EXPENSIVE_MEM_OPT | 0 | A bitmap indicating enabled expensive memory optimizations. These optimizations may lead to more JIT compilation time, but give some performance benefit. ### Note Currently, only the least significant bit is available. Available bits: 0: OpenCL address space alias analysis
CL_CONFIG_CPU_STREAMING_ALWAYS | False | Controls whether non-temporal instructions are used.

Parent topic: Compilation

## See Also

Qopenmp compiler option
parallel, Qparallel compiler option
prof-gen, Qprof-gen compiler option
Thread Affinity Interface