MPI2007 Flag Description
Lenovo Global Technology ThinkSystem SR950 (Intel Xeon Platinum 8180 CPU, 2.50 GHz)
Copyright © 2012 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 AVX instructions.
May generate Intel® AVX-512 Foundation instructions,Intel® AVX-512 Conflict Detectio
instructions, Intel® AVX-512 Doubleword and Quadword instructions, Intel® AVX-51
Byte and Word instructions, Intel® AVX-512 Vector Length extensions, Intel® AVX2,VX
SSE4.2, SSE4.1, SSSE3, SSE3, SSE2 and SSE instructions for Intel® processors.
Optimizes for a future Intel® processor. Available in compiler version 15 update 1
and later.
-
- -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 AVX instructions.
May generate Intel® AVX-512 Foundation instructions,Intel® AVX-512 Conflict Detectio
instructions, Intel® AVX-512 Doubleword and Quadword instructions, Intel® AVX-51
Byte and Word instructions, Intel® AVX-512 Vector Length extensions, Intel® AVX2,VX
SSE4.2, SSE4.1, SSSE3, SSE3, SSE2 and SSE instructions for Intel® processors.
Optimizes for a future Intel® processor. Available in compiler version 15 update 1
and later.
-
- -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 AVX instructions.
May generate Intel® AVX-512 Foundation instructions,Intel® AVX-512 Conflict Detectio
instructions, Intel® AVX-512 Doubleword and Quadword instructions, Intel® AVX-51
Byte and Word instructions, Intel® AVX-512 Vector Length extensions, Intel® AVX2,VX
SSE4.2, SSE4.1, SSSE3, SSE3, SSE2 and SSE instructions for Intel® processors.
Optimizes for a future Intel® processor. Available in compiler version 15 update 1
and later.
-
- -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 AVX instructions.
May generate Intel® AVX-512 Foundation instructions,Intel® AVX-512 Conflict Detectio
instructions, Intel® AVX-512 Doubleword and Quadword instructions, Intel® AVX-51
Byte and Word instructions, Intel® AVX-512 Vector Length extensions, Intel® AVX2,VX
SSE4.2, SSE4.1, SSSE3, SSE3, SSE2 and SSE instructions for Intel® processors.
Optimizes for a future Intel® processor. Available in compiler version 15 update 1
and later.
-
- -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 Lenovo-SPECmpiM_Platform_Flags
Lenovo SPECmpi 2007 Platform Flag Description
Machine Configurations
BIOS settings
Maximum Performance
mode will maximize the absolute performance of the system without regard for power.
In this mode, power consumption is a don't care.
Things like fan speed and heat output of the system may increase in addition to power consumption.
Efficiency of the system may go down in this mode, but the absolute performance may increase depending on the workload that is running.
Hyper-Threading
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.
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.
Values for this BIOS option can be:
Disabled: The LLC is treated as one cluster when this option is disabled
Enabled: Utilizes LLC capacity more efficiently and reduces latency due to core/IMC proximity.
This may provide performance improvement on NUMA-aware operating systems
Linux Kernel Parameter
intel_idle.max_cstate=0
Disable intel_idle driver from control C State
intel_pstate=disable
Disable intel_idle driver from control P State
Platform settings from EM64T_Intel121_flags
SPEC MPI2007 Flag Description for the Intel(R) C++ Compiler 12.1
for IA32 and Intel 64 applications and Intel(R) Fortran Compiler 12.1 for IA32 and Intel 64
applications
Intel(R) MPI Library 4.0.3 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.
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 Sep 12 12:24:39 2018 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)