MPI2007 Flag Description
Hewlett Packard Enterprise SGI 8600 (Intel Xeon Gold 6148, 2.40 GHz)
Test sponsored by HPE
Base Optimization Flags
-
- -O3
![[user]](http://www.spec.org/auto/mpi2007/flags/user.png)
- COPTIMIZE
-
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
- COPTIMIZE
-
May generate Intel(R) Advanced Vector Extensions 512 (Intel(R) AVX-512) Foundation instructions, Intel(R) AVX-512 Conflict Detection instructions, Intel(R) AVX-512 Doubleword and Quadword instructions, Intel(R) AVX-512 Byte and Word instructions and Intel(R) AVX-512 Vector Length extensions, as well as the instructions enabled with CORE-AVX2.
-
- -no-prec-div
- COPTIMIZE
-
(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
- CXXOPTIMIZE
-
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
- CXXOPTIMIZE
-
May generate Intel(R) Advanced Vector Extensions 512 (Intel(R) AVX-512) Foundation instructions, Intel(R) AVX-512 Conflict Detection instructions, Intel(R) AVX-512 Doubleword and Quadword instructions, Intel(R) AVX-512 Byte and Word instructions and Intel(R) AVX-512 Vector Length extensions, as well as the instructions enabled with CORE-AVX2.
-
- -no-prec-div
- CXXOPTIMIZE
-
(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
- FOPTIMIZE
-
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
- FOPTIMIZE
-
May generate Intel(R) Advanced Vector Extensions 512 (Intel(R) AVX-512) Foundation instructions, Intel(R) AVX-512 Conflict Detection instructions, Intel(R) AVX-512 Doubleword and Quadword instructions, Intel(R) AVX-512 Byte and Word instructions and Intel(R) AVX-512 Vector Length extensions, as well as the instructions enabled with CORE-AVX2.
-
- -no-prec-div
- FOPTIMIZE
-
(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
- COPTIMIZE, FOPTIMIZE
-
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
- COPTIMIZE, FOPTIMIZE
-
May generate Intel(R) Advanced Vector Extensions 512 (Intel(R) AVX-512) Foundation instructions, Intel(R) AVX-512 Conflict Detection instructions, Intel(R) AVX-512 Doubleword and Quadword instructions, Intel(R) AVX-512 Byte and Word instructions and Intel(R) AVX-512 Vector Length extensions, as well as the instructions enabled with CORE-AVX2.
-
- -no-prec-div
- COPTIMIZE, FOPTIMIZE
-
(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.
-
Base Other Flags
-
- -lmpi
- EXTRA_LIBS
-
MPI library.
-
- EXTRA_LIBS
-
MPI library.
-
- -lmpi
- EXTRA_LIBS
-
MPI library.
-
- -lmpi
- EXTRA_LIBS
-
MPI library.
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:
-
-
SGI MPT 2.0x options and environment variables
Job startup command and options
mpiexec_mpt [ global_opts ] local_opts cmd [ : local_opts cmd ] ...
The mpiexec_mpt command launches a Message Passing Toolkit (MPT) MPI program in a batch
scheduler-managed cluster environment. mpiexec_mpt uses the list of cluster nodes it
receives from the batch scheduler to generate and issue an appropriate mpirun command to
launch the multi-node job.
-n <# of processes> or -np <# of processes>
Use this option to set the number of MPI processes to run the current arg-set.
mpiexec [ global_opts ] local_opts cmd [ : local_opts cmd ] ...
The PBS Pro's mpiexec command provides the standard mpiexec interface on the Altix
running ProPack 4 or greater. It provides equivalent functionality to mpiexec_mpt.
Environment variables
MPI_REQUEST_MAX
Determines the maximum number of nonblocking sends and
receives that can simultaneously exist for any single MPI
process. MPI generates an error message if this limit
(or the default, if not set) is exceeded. Default: 16384
MPI_TYPE_MAX
Determines the maximum number of data types that can
simultaneously exist for any single MPI process.
MPI generates an error message if this limit (or the default,
if not set) is exceeded. Default: 1024
MPI_IB_RAILS
If the MPI library uses the IB driver as the inter-host
interconnect it will by default use a single IB fabric.
If this is set to 2, the library will try to make use of
multiple available separate IB fabrics and split MPI traffic across them. Default: 1
MPI_CONNECTIONS_THRESHOLD
For very large MPI jobs the time and resource cost to create an InfiniBand connection between
every pair of ranks at job start time may be prodigious. If this variable is set to a number
no greater than the number of ranks, then MPT will create InfiniBand RC Queue Pairs (QPs)
lazily on a demand basis. If this variable is set to a number greater than the number of ranks
then MPT will attempt to allocate all the InfiniBand RC QPs it needs at job start. If this
varibale is not modified and InfiniBand RC QPs are in use then MPT will compare the default
value against the number of ranks with the above criteria. If this is not modified and InfiniBand
XRC QPs are in use then MPT will attempt to allocate the QPs at job launch but may need to switch
to lazy allocation if the space needs are too large. Default: 1025
MPI_IB_DEVS
Directs MPT to open specific IB ports in each rank. If MPI_IB_DEVS is empty or not defined, MPT will assign ranks to IB ports by the formula
"local rank modulo number of ports." The first rank on each host will use the first port on that host, etc. By default MPT will only use the
first working port on the first HCA with a working port.
Other Tuning Information
ulimit -s unlimited
Removes limits on the maximum size of the automatically-
extended stack region of the current process and each
process it creates.
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 Oct 25 17:11:42 2017 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)