OMP2012 Flag Description
Lenovo Global Technology ThinkSystem SR950

Copyright © 2012 Intel Corporation. All Rights Reserved.

Base Compiler Invocation

C benchmarks

C++ benchmarks

Fortran benchmarks

Base Portability Flags




Base Optimization Flags

C benchmarks

C++ benchmarks

Fortran benchmarks

Implicitly Included Flags

This section contains descriptions of flags that were included implicitly by other flags, but which do not have a permanent home at SPEC.

Shell, Environment, and Other Software Settings

Open MP Tuning Flags


    The KMP_AFFINITY environment variable uses the following general syntax:



    For example, to list a machine topology map, specify KMP_AFFINITY=verbose,none to use a modifier of verbose and a type of none.

    The following table describes the supported specific arguments.








    Optional. String consisting of keyword and specifier.

    • granularity=<specifier>
      takes the following specifiers: fine, thread, and core

    • norespect

    • noverbose

    • nowarnings

    • proclist={<proc-list>}

    • respect

    • verbose

    • warnings



    Required string. Indicates the thread affinity to use.

    • compact

    • disabled

    • explicit

    • none

    • scatter

    • logical (deprecated; instead use compact, but omit any permute value)

    • physical (deprecated; instead use scatter, possibly with an offset value)

    The logical and physical types are deprecated but supported for backward compatibility.



    Optional. Positive integer value. Not valid with type values of explicit, none, or disabled.



    Optional. Positive integer value. Not valid with type values of explicit, none, or disabled.

    Affinity Types

    Type is the only required argument.

    type = none (default)

    Does not bind OpenMP threads to particular thread contexts; however, if the operating system supports affinity, the compiler still uses the OpenMP thread affinity interface to determine machine topology. Specify KMP_AFFINITY=verbose,none to list a machine topology map.

    type = compact

    Specifying compact assigns the OpenMP thread <n>+1 to a free thread context as close as possible to the thread context where the <n> OpenMP thread was placed. For example, in a topology map, the nearer a node is to the root, the more significance the node has when sorting the threads.

    type = disabled

    Specifying disabled completely disables the thread affinity interfaces. This forces the OpenMP run-time library to behave as if the affinity interface was not supported by the operating system. This includes the low-level API interfaces such as kmp_set_affinity and kmp_get_affinity, which have no effect and will return a nonzero error code.

    type = explicit

    Specifying explicit assigns OpenMP threads to a list of OS proc IDs that have been explicitly specified by using the proclist= modifier, which is required for this affinity type.

    type = scatter

    Specifying scatter distributes the threads as evenly as possible across the entire system. scatter is the opposite of compact; so the leaves of the node are most significant when sorting through the machine topology map.

    Deprecated Types: logical and physical

    Types logical and physical are deprecated and may become unsupported in a future release. Both are supported for backward compatibility.

    For logical and physical affinity types, a single trailing integer is interpreted as an offset specifier instead of a permute specifier. In contrast, with compact and scatter types, a single trailing integer is interpreted as a permute specifier.

    Specifying logical assigns OpenMP threads to consecutive logical processors, which are also called hardware thread contexts. The type is equivalent to compact, except that the permute specifier is not allowed. Thus, KMP_AFFINITY=logical,n is equivalent to KMP_AFFINITY=compact,0,n  (this equivalence is true regardless of the whether or not a  granularity=fine modifier is present).

    Permute and offset combinations

    For both compact and scatter, permute and offset are allowed; however, if you specify only one integer, the compiler interprets the value as a permute specifier. Both permute and offset default to 0.  

    The permute specifier controls which levels are most significant when sorting the machine topology map. A value for permute forces the mappings to make the specified number of most significant levels of the sort the least significant, and it inverts the order of significance. The root node of the tree is not considered a separate level for the sort operations.

    The offset specifier indicates the starting position for thread assignment.

    Modifier Values for Affinity Types

    Modifiers are optional arguments that precede type. If you do not specify a modifier, the noverbose, respect, and granularity=core modifiers are used automatically.

    Modifiers are interpreted in order from left to right, and can negate each other. For example, specifying KMP_AFFINITY=verbose,noverbose,scatter is therefore equivalent to setting KMP_AFFINITY=noverbose,scatter, or just KMP_AFFINITY=scatter.

    modifier = noverbose (default)

    Does not print verbose messages.

    modifier = verbose

    Prints messages concerning the supported affinity. The messages include information about the number of packages, number of cores in each package, number of thread contexts for each core, and OpenMP thread bindings to physical thread contexts.

    Information about binding OpenMP threads to physical thread contexts is indirectly shown in the form of the mappings between hardware thread contexts and the operating system (OS) processor (proc) IDs. The affinity mask for each OpenMP thread is printed as a set of OS processor IDs.


    KMP_LIBRARY = { throughput | turnaround | serial }, Selects the OpenMP run-time library execution mode. The options for the variable value are throughput, turnaround, and serial.

    Execution modes

    The compiler with OpenMP enables you to run an application under different execution modes that can be specified at run time. The libraries support the serial, turnaround, and throughput modes.


    The serial mode forces parallel applications to run on a single processor.


    In a dedicated (batch or single user) parallel environment where all processors are exclusively allocated to the program for its entire run, it is most important to effectively utilize all of the processors all of the time. The turnaround mode is designed to keep active all of the processors involved in the parallel computation in order to minimize the execution time of a single job. In this mode, the worker threads actively wait for more parallel work, without yielding to other threads.

    Avoid over-allocating system resources. This occurs if either too many threads have been specified, or if too few processors are available at run time. If system resources are over-allocated, this mode will cause poor performance. The throughput mode should be used instead if this occurs.


    In a multi-user environment where the load on the parallel machine is not constant or where the job stream is not predictable, it may be better to design and tune for throughput. This minimizes the total time to run multiple jobs simultaneously. In this mode, the worker threads will yield to other threads while waiting for more parallel work.

    The throughput mode is designed to make the program aware of its environment (that is, the system load) and to adjust its resource usage to produce efficient execution in a dynamic environment. This mode is the default.


    KMP_BLOCKTIME = value. 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.


    KMP_STACKSIZE = value. 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: b (bytes), k (kilobytes), m (megabytes), g (gigabytes), or t (terabytes) to specify the units. 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 -parallel.


    Sets the maximum number of threads to use for OpenMP* parallel regions if no other value is specified in the application. This environment variable applies to both -openmp and -parallel. Example syntax on a Linux system with 8 cores: export OMP_NUM_THREADS=8


    OMP_DYNAMIC={ 1 | 0 } Enables (1, true) or disables (0,false) the dynamic adjustment of the number of threads.


    OMP_SCHEDULE={ type,[chunk size]} Controls the scheduling of the for-loop work-sharing construct. type can be either of static,dynamic,guided,runtime chunk size should be positive integer


    OMP_NESTED={ 1 | 0 } Enables creation of new teams in case of nested parallel regions (1,true) or serializes (0,false) all nested parallel regions. Default is 0.

  • Firmware / BIOS / Microcode Settings

    Operating Modes Selections: (Default="Efficiency -Favor Performance")
    The average customer doesn't know the best way to set each individual power/performance feature for their specific environment. Because of this, a menu option is provided that can help a customer optimize the system for things such as minimum power usage/acoustic levels, maximum efficiency, Energy Star optimization, or maximum performance.
    C-states reduce CPU idle power. There are three options in this mode: Legacy, Autonomous, Disable.
    C1 Enhanced Mode:
    Enabling C1E (C1 enhanced) state can save power by halting CPU cores that are idle.
    Turbo Mode:
    Enabling turbo mode can boost the overall CPU performance when all CPU cores are not being fully utilized. A CPU core can run above its rated frequency for a short perios of time when it is in turbo mode.
    Enabling Hyper-Threading let operating system addresses two virtual or logical cores for a physical presented core. Workloads can be shared between virtual or logical cores when possible. The main function of hyper-threading is to increase the number of independent instructions in the pipeline for using the processor resources more efficiently.
    Execute Disable Bit:
    The execute disable bit allows memory to be marked as executable or non-executable when used with a supporting operating system. This can improve system security by configuring the processor to raise an error to the operating system when code attempts to run in non-executable memory.
    DCA capable I/O devices such as network controllers can place data directly into the CPU cache, which improves response time.
    Power/Performance Bias:
    Power/Performance bias determines how aggressively the CPU will be power managed and placed into turbo. With "Platform Controlled", the system controls the setting. Selecting "OS Controlled" allows the operating system to control it.
    Per Core P-state:
    When per-core P-states are enabled, each physical CPU core can operate at separate frequencies. If disabled, all cores in a package will operate at the highest resolved frequency of all active threads.
    CPU Frequency Limits:
    The maximum turbo frequency can be restricted with turbo limiting to a frequency that is between the maximum turbo frequency and the rated frequency for the CPU installed.
    Energy Efficient Turbo:
    When energy efficient turbo is enabled, the CPU's optimal turbo frequency will be tuned dynamically based on CPU utilization.
    Uncore Frequency Scaling:
    When enabled, the CPU uncore will dynamically change speed based on the workload.
    MONITOR/MWAIT instructions are used to engage C-states.
    Sub-NUMA Cluster (SNC):
    SNC breaks up the last level cache (LLC) into disjoint clusters based on address range, with each cluster bound to a subset of the memory controllers in the system. SNC improves average latency to the LLC and memory. SNC is a replacement for the cluster on die (COD) feature found in previous processor families. For a multi-socketed system, all SNC clusters are mapped to unique NUMA domains. (See also IMC interleaving.) Values for this BIOS option can be:
    Snoop Preference:
    Select the appropriate snoop mode based on the workload. There are two snoop modes: "HS w. Directory + OSB +HitME cache" and "Home Snoop". Default is "HS w. Directory + OSB +HitME cache".
    XPT Prefetcher
    XPT prefetch is a mechanism that enables a read request that is being sent to the last level cache to speculatively issue a copy of that read to the memory controller prefetching
    UPI Prefetcher
    UPI prefetch is a mechanism to get the memroy read started early on DDR bus. The UPI receive path will spawn a memory read to the memory controller prefetcher.
    Patrol Scrub:
    Patrol Scrub is a memory RAS feature which runs a background memory scrub against all DIMMs. Can negatively impact performance.
    DCU Streamer Prefetcher:
    DCU (Level 1 Data Cache) streamer prefetcher is an L1 data cache prefetcher. Lightly threaded applications and some benchmarks can benefit from having the DCU streamer prefetcher enabled. Default setting is Enable.
    Stale A to S
    The in-memory directory has three states: invalid (I), snoopAll (A), and shared (S). Invalid (I) state means the data is clean and does not exist in any other socket`s cache. The snoopAll (A) state means the data may exist in another socket in exclusive or modified state. Shared (S) state means the data is clean and may be shared across one or more socket`s caches. When doing a read to memory, if the directory line is in the A state we must snoop all the other sockets because another socket may have the line in modified state. If this is the case, the snoop will return the modified data. However, it may be the case that a line is read in A state and all the snoops come back a miss. This can happen if another socket read the line earlier and then silently dropped it from its cache without modifying it. Values for this BIOS option can be: Stale A to S may be beneficial in a workload where there are many cross-socket reads.
    LLC Dead Line Allocation
    In some Intel CPU caching schemes, mid-level cache (MLC) evictions are filled into the last level cache (LLC). If a line is evicted from the MLC to the LLC, the core can flag the evicted MLC lines as "dead." This means that the lines are not likely to be read again. This option allows dead lines to be dropped and never fill the LLC if the option is disabled. Values for this BIOS option can be:
    Adjacent Cache Prefetch:
    Lightly threaded applications and some benchmarks can benefit from having the adjacent cache line prefetch enabled. Default is enable.
    Intel Virtualization Technology:
    Intel Virtualization Technology allows a platform to run multiple operating systems and applications in independent partitions, so that one computer system can function as multiple virtual system. Default is enable.
    Acounstic Mode
    By using acoustic mode, the user has some control over the fan speeds and airflow (and noise) that is produced by the system fans. This mode can be used for noise or airflow concerns in the user environment. As a result, Mode1,2,3,4,5 increase the possibility that the node might have to be throttled to maintain cooling within the fan speed limitation. If there is power or thermal demanding PCI card installed in the chassis, acoustic mode is automatically disabled.

    Flag description origin markings:

    [user] Indicates that the flag description came from the user flags file.
    [suite] Indicates that the flag description came from the suite-wide flags file.
    [benchmark] Indicates that the flag description came from a per-benchmark flags file.

    The flags files that were used to format this result can be browsed at,

    You can also download the XML flags sources by saving the following links:,

    For questions about the meanings of these flags, please contact the tester.
    For other inquiries, please contact
    Copyright 2012-2018 Standard Performance Evaluation Corporation
    Tested with SPEC OMP2012 v1.0.
    Report generated on Wed Sep 12 12:15:43 2018 by SPEC OMP2012 flags formatter v538.