MPI2007 Flag Description
SGI SGI Rackable C2005-TY3 (Intel Xeon X5687, 3.60 GHz)
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:
-
- -xSSE4.2
- COPTIMIZE
-
Code is optimized for Intel(R) processors with support for SSE 4.2 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
- 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:
-
- -xSSE4.2
- CXXOPTIMIZE
-
Code is optimized for Intel(R) processors with support for SSE 4.2 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
- 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:
-
- -xSSE4.2
- FOPTIMIZE
-
Code is optimized for Intel(R) processors with support for SSE 4.2 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
- 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:
-
- -xSSE4.2
- COPTIMIZE, FOPTIMIZE
-
Code is optimized for Intel(R) processors with support for SSE 4.2 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
- 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_BUFS_THRESHOLD
Determines whether MPT uses per-host or per-process message
buffers for communicating with other hosts. Per-host buffers
are generally faster but for jobs running across many hosts they
can consume a prodigious amount of memory. MPT will use per-
host buffers for jobs using up to and including this many hosts
and will use per-process buffers for larger host counts.
Default: 64
MPI_DSM_DISTRIBUTE (toggle)
If set, NUMA job placement mode is activated. This mode ensures that each
MPI process gets a unique CPU and physical memory on the node
with which that CPU is associated. Currently, the CPUs are
chosen by simply starting at relative CPU 0 and incrementing
until all MPI processes have been forked. Default: Not enabled
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
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 Tue Jul 22 13:43:52 2014 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)