OMP2012 Flag Description
xFusion FusionServer 2288H V7 (Intel Xeon Platinum 8490H, 1.90 GHz)

Copyright © 2012 Intel Corporation. All Rights Reserved.


Base Compiler Invocation

C benchmarks

C++ benchmarks

Fortran benchmarks


Base Portability Flags

350.md

357.bt331

363.swim

367.imagick


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

  • KMP_AFFINITY

    The KMP_AFFINITY environment variable uses the following general syntax:

    Syntax

    KMP_AFFINITY=[<modifier>,...]<type>[,<permute>][,<offset>]

    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.

    Argument

    Default

    Description

    modifier

    noverbose

    respect

    granularity=core

    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

    type

    none

    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.

    permute

    0

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

    offset

    0

    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

    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.

    Serial

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

    Turnaround

    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.

    Throughput

    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

    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

    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.

  • OMP_NUM_THREADS

    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 -qopenmp and -parallel. Example syntax on a Linux system with 8 cores: export OMP_NUM_THREADS=8

  • OMP_DYNAMIC

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

  • OMP_SCHEDULE

    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

    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

    Hardware Prefetcher (Default = Enabled)

    This BIOS option allows the enabling/disabling of a processor mechanism to prefetch data into the cache according to a pattern-recognition algorithm In some cases, setting this option to Disabled may improve performance. Users should only disable this option after performing application benchmarking to verify improved performance in their environment.

    Turbo Mode (Default = Enabled)

    Intel Turbo boost Technology, Enabling this option allows the processor cores to automatically increase its frequency and increasing performance if it is running below power, temperature.

    Enable LP [Global] (Default = Enabled)

    The Intel Hyper-Threading knob has been renamed Enable LP [Global] to represent the number of logical processors (LP). This feature allows enabling or disabling of logical processor cores on processors supporting Intel Hyper-Threading. Recommended default setting is All LPs. In some cases, setting this option to Single LP can improve performance.

    Values for this BIOS setting can be:

    Enabled: Each physical processor core operates as two logical processor cores. Enabling this option allows to use processor resources more efficiently, enabling multiple threads to run on each core and increases processor throughput, improving overall performance on threaded software.

    Single LP: Each physical core operates as only one logical processor core.

    Performance Profile (Default = Custom)

    Performance Profiles is a feature that allows customer to tune resources in their servers by selecting pre-configured performance profiles.

    Values for this BIOS setting can be:

    Custom: Allows the user to setup all of the BIOS options according to customer's requirement.

    Performance: Maximize the performance of the server.

    Efficiency: Maximize the power efficiency of the server.

    Load Balance: The system's performance and power consumption will be adjusted automatically according to the loading.

    CPU C6 Report (Default = Disabled)

    Enable or disable reporting of the CPU C6 State (ACPI C3) to the OS.

    Enhanced Halt State (C1E) (Default = Disabled)

    When set to Enabled, the processor is allowed to switch to nimimum performance and save power when idle.

    Sub NUMA Cluster(SNC)(Default = Disabled)

    Sub NUMA Clustering (SNC) is a feature for breaking up the LLC into disjoint clusters based on address range,with each cluster bound to a subset of the memory controllers in the system.It improves average latency to the LLC.

    Values for this BIOS option can be:

    Disabled: SNC disabled will support 1-cluster and 4-way IMC interleave.

    Enable SNC2 (2-clusters): SNC2 Enabled supports 2-clusters SNC and 2-way IMC interleave.

    Enable SNC4 (4-clusters): SNC2 Enabled supports 4-clusters SNC and 1-way IMC interleave.

    Last Level Cache (LLC) Prefetch (Default = Enabled)

    The last level cache (LLC) prefetch is a prefetcher added to the Intel Xeon Scalable processor family as a result of the non-inclusive cache architecture. The LLC prefetcher is an additional prefetch mechanism on top of the existing prefetchers that prefetch data into the core Data Cache Unit (DCU) and Mid-Level Cache (MLC or second-level cache (L2)). Enabling LLC prefetch gives the core prefetcher the ability to prefetch data directly into the LLC without necessarily filling into the L1 and L2 cache. In some cases, setting this option to disabled can improve performance.

    Values for this BIOS option can be:

    Disabled: Disables the LLC prefetcher. The other core prefetchers are unaffected.

    Enabled: Gives the core prefetcher the ability to prefetch data directly to the LLC.

    Adaptive Double Device Data Correction (ADDDC) Sparing (Default = Enabled)

    Adaptive Double Device Data Correction (ADDDC), which is an enhanced feature to DDDC. This function is used to correct data errors on two memory particles, ADDDC still has single-particle multi-bit error correction capability after the first particle failure occurs and is replaced.

    Values for this BIOS option can be:

    Enabled: Enable the ADDDC Sparing function.

    Disabled: Disable the ADDDC Sparing function.


    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
    http://www.spec.org/omp2012/flags/Intel-ic19-linux64.20210507.html,
    http://www.spec.org/omp2012/flags/xFusion-Platform-Settings-SPR-V1.0.html.

    You can also download the XML flags sources by saving the following links:
    http://www.spec.org/omp2012/flags/Intel-ic19-linux64.20210507.xml,
    http://www.spec.org/omp2012/flags/xFusion-Platform-Settings-SPR-V1.0.xml.


    For questions about the meanings of these flags, please contact the tester.
    For other inquiries, please contact webmaster@spec.org
    Copyright 2012-2023 Standard Performance Evaluation Corporation
    Tested with SPEC OMP2012 v1.1.
    Report generated on Wed Jan 11 14:04:12 2023 by SPEC OMP2012 flags formatter v538.