MPI2007 Flag Description
xFusion FusionServer XH321 V7
Copyright © 2013 Intel Corporation. All Rights Reserved.
Base Optimization Flags
-
- -O3
![[user]](http://www.spec.org/auto/mpi2007/flags/user.png)
- OPTIMIZE
-
Enables O2 optimizations plus more aggressive optimizations, such as prefetching, scalar replacement, and loop and memory access transformations. Enables optimizations for maximum speed, such as:
- Loop unrolling, including instruction scheduling
- Code replication to eliminate branches
- Padding the size of certain power-of-two arrays to allow more efficient cache use.
On IA-32 and Intel EM64T processors, when O3 is used with options -ax or -x (Linux) or with options /Qax or /Qx (Windows), the compiler performs more aggressive data dependency analysis than for O2, which may result in longer compilation times.
The O3 optimizations may not cause higher performance unless loop and memory access transformations take place. The optimizations may slow down code in some cases compared to O2 optimizations.
The O3 option is recommended for applications that have loops that heavily use floating-point calculations and process large data sets. On IA-32 Windows platforms, -O3 sets the following:
/GF (/Qvc7 and above), /Gf (/Qvc6 and below), and /Ob2
- Includes:
-
- -xCORE-AVX512
- OPTIMIZE
-
Code is optimized for Intel(R) processors with support for CORE-AVX512 instructions.
The resulting code may contain unconditional use of features that are not supported
on other processors. This option also enables new optimizations in addition to
Intel processor-specific optimizations including advanced data layout and code
restructuring optimizations to improve memory accesses for Intel processors.
Do not use this option if you are executing a program on a processor that
is not an Intel processor. If you use this option on a non-compatible processor
to compile the main program (in Fortran) or the function main() in C/C++, the
program will display a fatal run-time error if they are executed on unsupported
processors.
-
- -no-prec-div
- OPTIMIZE
-
(disable/enable[default] -[no-]prec-div)
-prec-div improves precision of floating-point divides. It has a slight impact on speed. -no-prec-div disables this option and enables optimizations that give slightly less precise results than full IEEE division.
When you specify -no-prec-div along with some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.
However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, do not use -no-prec-div which will enable the default -prec-div and the result is more accurate, with some loss of performance.
-
-
-
-
- -O3
- OPTIMIZE
-
Enables O2 optimizations plus more aggressive optimizations, such as prefetching, scalar replacement, and loop and memory access transformations. Enables optimizations for maximum speed, such as:
- Loop unrolling, including instruction scheduling
- Code replication to eliminate branches
- Padding the size of certain power-of-two arrays to allow more efficient cache use.
On IA-32 and Intel EM64T processors, when O3 is used with options -ax or -x (Linux) or with options /Qax or /Qx (Windows), the compiler performs more aggressive data dependency analysis than for O2, which may result in longer compilation times.
The O3 optimizations may not cause higher performance unless loop and memory access transformations take place. The optimizations may slow down code in some cases compared to O2 optimizations.
The O3 option is recommended for applications that have loops that heavily use floating-point calculations and process large data sets. On IA-32 Windows platforms, -O3 sets the following:
/GF (/Qvc7 and above), /Gf (/Qvc6 and below), and /Ob2
- Includes:
-
- -xCORE-AVX512
- OPTIMIZE
-
Code is optimized for Intel(R) processors with support for CORE-AVX512 instructions.
The resulting code may contain unconditional use of features that are not supported
on other processors. This option also enables new optimizations in addition to
Intel processor-specific optimizations including advanced data layout and code
restructuring optimizations to improve memory accesses for Intel processors.
Do not use this option if you are executing a program on a processor that
is not an Intel processor. If you use this option on a non-compatible processor
to compile the main program (in Fortran) or the function main() in C/C++, the
program will display a fatal run-time error if they are executed on unsupported
processors.
-
- -no-prec-div
- OPTIMIZE
-
(disable/enable[default] -[no-]prec-div)
-prec-div improves precision of floating-point divides. It has a slight impact on speed. -no-prec-div disables this option and enables optimizations that give slightly less precise results than full IEEE division.
When you specify -no-prec-div along with some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.
However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, do not use -no-prec-div which will enable the default -prec-div and the result is more accurate, with some loss of performance.
-
-
-
-
- -O3
- OPTIMIZE
-
Enables O2 optimizations plus more aggressive optimizations, such as prefetching, scalar replacement, and loop and memory access transformations. Enables optimizations for maximum speed, such as:
- Loop unrolling, including instruction scheduling
- Code replication to eliminate branches
- Padding the size of certain power-of-two arrays to allow more efficient cache use.
On IA-32 and Intel EM64T processors, when O3 is used with options -ax or -x (Linux) or with options /Qax or /Qx (Windows), the compiler performs more aggressive data dependency analysis than for O2, which may result in longer compilation times.
The O3 optimizations may not cause higher performance unless loop and memory access transformations take place. The optimizations may slow down code in some cases compared to O2 optimizations.
The O3 option is recommended for applications that have loops that heavily use floating-point calculations and process large data sets. On IA-32 Windows platforms, -O3 sets the following:
/GF (/Qvc7 and above), /Gf (/Qvc6 and below), and /Ob2
- Includes:
-
- -xCORE-AVX512
- OPTIMIZE
-
Code is optimized for Intel(R) processors with support for CORE-AVX512 instructions.
The resulting code may contain unconditional use of features that are not supported
on other processors. This option also enables new optimizations in addition to
Intel processor-specific optimizations including advanced data layout and code
restructuring optimizations to improve memory accesses for Intel processors.
Do not use this option if you are executing a program on a processor that
is not an Intel processor. If you use this option on a non-compatible processor
to compile the main program (in Fortran) or the function main() in C/C++, the
program will display a fatal run-time error if they are executed on unsupported
processors.
-
- -no-prec-div
- OPTIMIZE
-
(disable/enable[default] -[no-]prec-div)
-prec-div improves precision of floating-point divides. It has a slight impact on speed. -no-prec-div disables this option and enables optimizations that give slightly less precise results than full IEEE division.
When you specify -no-prec-div along with some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.
However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, do not use -no-prec-div which will enable the default -prec-div and the result is more accurate, with some loss of performance.
-
-
-
-
- -O3
- OPTIMIZE
-
Enables O2 optimizations plus more aggressive optimizations, such as prefetching, scalar replacement, and loop and memory access transformations. Enables optimizations for maximum speed, such as:
- Loop unrolling, including instruction scheduling
- Code replication to eliminate branches
- Padding the size of certain power-of-two arrays to allow more efficient cache use.
On IA-32 and Intel EM64T processors, when O3 is used with options -ax or -x (Linux) or with options /Qax or /Qx (Windows), the compiler performs more aggressive data dependency analysis than for O2, which may result in longer compilation times.
The O3 optimizations may not cause higher performance unless loop and memory access transformations take place. The optimizations may slow down code in some cases compared to O2 optimizations.
The O3 option is recommended for applications that have loops that heavily use floating-point calculations and process large data sets. On IA-32 Windows platforms, -O3 sets the following:
/GF (/Qvc7 and above), /Gf (/Qvc6 and below), and /Ob2
- Includes:
-
- -xCORE-AVX512
- OPTIMIZE
-
Code is optimized for Intel(R) processors with support for CORE-AVX512 instructions.
The resulting code may contain unconditional use of features that are not supported
on other processors. This option also enables new optimizations in addition to
Intel processor-specific optimizations including advanced data layout and code
restructuring optimizations to improve memory accesses for Intel processors.
Do not use this option if you are executing a program on a processor that
is not an Intel processor. If you use this option on a non-compatible processor
to compile the main program (in Fortran) or the function main() in C/C++, the
program will display a fatal run-time error if they are executed on unsupported
processors.
-
- -no-prec-div
- OPTIMIZE
-
(disable/enable[default] -[no-]prec-div)
-prec-div improves precision of floating-point divides. It has a slight impact on speed. -no-prec-div disables this option and enables optimizations that give slightly less precise results than full IEEE division.
When you specify -no-prec-div along with some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.
However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, do not use -no-prec-div which will enable the default -prec-div and the result is more accurate, with some loss of performance.
-
-
-
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.
-
-
-
- -Ob_n
-
Specifies the level of inline function expansion.
Ob0 - Disables inlining of user-defined functions. Note that statement functions are always inlined.
Ob1 - Enables inlining when an inline keyword or an inline attribute is specified. Also enables inlining according to the C++ language.
Ob2 - Enables inlining of any function at the compiler's discretion.
-
- -O2
-
Enables optimizations for speed. This is the generally recommended optimization level. This option also enables:
- Inlining of intrinsics
- Intra-file interprocedural optimizations, which include:
- inlining
- constant propagation
- forward substitution
- routine attribute propagation
- variable address-taken analysis
- dead static function elimination
- removal of unreferenced variables
- The following capabilities for performance gain:
- constant propagation
- copy propagation
- dead-code elimination
- global register allocation
- global instruction scheduling and control speculation
- loop unrolling
- optimized code selection
- partial redundancy elimination
- strength reduction/induction variable simplification
- variable renaming
- exception handling optimizations
- tail recursions
- peephole optimizations
- structure assignment lowering and optimizations
- dead store elimination
On IA-32 Windows platforms, -O2 sets the following:
/Og, /Oi-, /Os, /Oy, /Ob2, /GF (/Qvc7 and above), /Gf (/Qvc6 and below), /Gs, and /Gy.
- Includes:
-
-
-
-
-
-
-
- -O1
-
Enables optimizations for speed and disables some optimizations that
increase code size and affect speed.
To limit code size, this option:
- Enables global optimization; this includes data-flow analysis, code motion, strength reduction and test replacement, split-lifetime analysis, and instruction scheduling.
- Disables intrinsic recognition and intrinsics inlining.
The O1 option may improve performance for applications with very large code size, many branches, and execution time not dominated by code within loops.
On IA-32 Windows platforms, -O1 sets the following:
/Qunroll0, /Oi-, /Op-, /Oy, /Gy, /Os, /GF (/Qvc7 and above), /Gf (/Qvc6 and below), /Ob2, and /Og
- Includes:
-
-
This result has been formatted using multiple flags files.
The "platform settings" from each of them appears next.
Platform settings from xFusion_x86_64_Intel_linux
SPEC MPI2007 Flag Description for the Intel(R) C++ Compiler for IA32 and Intel 64 applications and Intel(R) Fortran Compiler for IA32 and Intel 64 applications
Intel(R) MPI Library 4.1.1 for Linux* options and environment variables
Job startup command flags
-n <# of processes> or -np <# of processes> Use this option to set the number of MPI processes to run the current arg-set.
-perhost <# of processes>
Use this option to place the indicated number of consecutive MPI processes on every host in group round robin fashion. The number of processes to start is controlled by the option -n as usual.
--parallel-startup
Use this option to allow parallel fast starting of mpd daemons under one local root. No daemon checking is performed.
-genv <ENVVAR> <value>
Use this option to set the <ENVVAR> environment variable to the specified <value> for all MPI processes.
Environment variables
I_MPI_DEVICE=<device>[:<provider>]
Select the particular network fabric to be used.
sock - Sockets
shm - Shared-memory only (no sockets)
ssm - Combined sockets + shared memory (for clusters with SMP nodes)
rdma - RDMA-capable network fabrics including InfiniBand*, Myrinet* (via DAPL*)
rdssm - Combined sockets + shared memory + DAPL* (for clusters with SMP nodes and RDMA-capable network fabrics)
I_MPI_FALLBACK_DEVICE=(enable|disable)
Set this environment variable to enable fallback to the available fabric. It is valid only for rdssm and rdma modes.
Fall back to the shared memory and/or socket fabrics if initialization of the DAPL* fabric fails. This is the default value.
Terminate the job if the fabric selected by the I_MPI_DEVICE environment variable cannot be initialized.
Platform settings from xfusion-specmpi-platform-flag
SPEC MPI software OS and BIOS Settings Descriptions for xFusion Platform systems
- 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.
For questions about the meanings of these flags, please contact the tester.
For other inquiries, please contact webmaster@spec.org
Copyright 2006-2010 Standard Performance Evaluation Corporation
Tested with SPEC MPI2007 v2.0.1.
Report generated on Wed Jan 11 14:04:48 2023 by SPEC MPI2007 flags formatter v1445.
![[benchmark]](http://www.spec.org/auto/mpi2007/flags/benchmark.png)
![[suite]](http://www.spec.org/auto/mpi2007/flags/suite.png)