CPU2006 Flag Description
NEC Corporation Express5800/R120b-2 (Intel Xeon X5687)
This result has been formatted using multiple flags files.
The "default header section" from each of them appears next.
Default header section from Intel-ic12.0-linux64-revB
SPEC CPU2006 Flag Description for the Intel(R) C++ and Fortran Compiler 12.0
for IA32 and Intel 64 applications
Copyright © 2006 Intel Corporation. All Rights Reserved.
Default header section from NEC-Intel-Linux-Settings-flags-revF
SPEC CPU2006 Software OS and BIOS tuning Descriptions NEC Express5800 Intel-based systems
applications
Copyright © 2007 Intel Corporation. All Rights Reserved.
Base Portability Flags
-
- -DSPEC_CPU_LP64
![[suite]](http://www.spec.org/auto/cpu2006/flags/suite.png)
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -nofor_main
![[user]](http://www.spec.org/auto/cpu2006/flags/user.png)
- LDPORTABILITY
-
This option specifies that the main program is not written in Fortran.
It is a link-time option that prevents the compiler from linking for_main.o
into applications.
For example, if the main program is written in C and calls a Fortran subprogram,
specify -nofor-main when compiling the program with the ifort command.
If you omit this option, the main program must be a Fortran program.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -nofor_main
- LDPORTABILITY
-
This option specifies that the main program is not written in Fortran.
It is a link-time option that prevents the compiler from linking for_main.o
into applications.
For example, if the main program is written in C and calls a Fortran subprogram,
specify -nofor-main when compiling the program with the ifort command.
If you omit this option, the main program must be a Fortran program.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -nofor_main
- LDPORTABILITY
-
This option specifies that the main program is not written in Fortran.
It is a link-time option that prevents the compiler from linking for_main.o
into applications.
For example, if the main program is written in C and calls a Fortran subprogram,
specify -nofor-main when compiling the program with the ifort command.
If you omit this option, the main program must be a Fortran program.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
-
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
Peak Portability Flags
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -nofor_main
- LDPORTABILITY
-
This option specifies that the main program is not written in Fortran.
It is a link-time option that prevents the compiler from linking for_main.o
into applications.
For example, if the main program is written in C and calls a Fortran subprogram,
specify -nofor-main when compiling the program with the ifort command.
If you omit this option, the main program must be a Fortran program.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -nofor_main
- LDPORTABILITY
-
This option specifies that the main program is not written in Fortran.
It is a link-time option that prevents the compiler from linking for_main.o
into applications.
For example, if the main program is written in C and calls a Fortran subprogram,
specify -nofor-main when compiling the program with the ifort command.
If you omit this option, the main program must be a Fortran program.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -nofor_main
- LDPORTABILITY
-
This option specifies that the main program is not written in Fortran.
It is a link-time option that prevents the compiler from linking for_main.o
into applications.
For example, if the main program is written in C and calls a Fortran subprogram,
specify -nofor-main when compiling the program with the ifort command.
If you omit this option, the main program must be a Fortran program.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
-
-
-
- -DSPEC_CPU_LP64
- PORTABILITY
-
This option is used to indicate that the host system's integers are 32-bits
wide, and longs and pointers are 64-bits wide. Not all benchmarks
recognize this macro, but the preferred practice for data model selection
applies the flags to all benchmarks; this flag description is a placeholder
for those benchmarks that do not recognize this macro.
Base Optimization Flags
-
- -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.
-
-
- -O3
- 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.
- Includes:
-
- -no-prec-div
- COPTIMIZE
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
-
- -parallel
- Yes
- COPTIMIZE
-
Tells the auto-parallelizer to generate multithreaded code for loops that can be safely executed in parallel.
To use this option, you must also specify option O2 or O3. The default numbers of threads spawned is equal to
the number of processors detected in the system where the binary is compiled. Can be changed by setting the
environment variable OMP_NUM_THREADS
-
-
-
- -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.
-
-
- -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.
- Includes:
-
- -no-prec-div
- CXXOPTIMIZE
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
-
-
-
- -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.
-
-
- -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.
- Includes:
-
- -no-prec-div
- FOPTIMIZE
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
-
- -parallel
- Yes
- FOPTIMIZE
-
Tells the auto-parallelizer to generate multithreaded code for loops that can be safely executed in parallel.
To use this option, you must also specify option O2 or O3. The default numbers of threads spawned is equal to
the number of processors detected in the system where the binary is compiled. Can be changed by setting the
environment variable OMP_NUM_THREADS
-
-
- -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.
-
-
- -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.
- Includes:
-
- -no-prec-div
- COPTIMIZE, FOPTIMIZE
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
-
- -parallel
- Yes
- COPTIMIZE, FOPTIMIZE
-
Tells the auto-parallelizer to generate multithreaded code for loops that can be safely executed in parallel.
To use this option, you must also specify option O2 or O3. The default numbers of threads spawned is equal to
the number of processors detected in the system where the binary is compiled. Can be changed by setting the
environment variable OMP_NUM_THREADS
-
-
Peak Optimization Flags
-
- -xSSE4.2
- PASS2_CFLAGS, PASS2_LDFLAGS
-
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.
-
-
-
- -O3
- PASS2_CFLAGS, PASS2_LDFLAGS
-
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.
- Includes:
-
- -no-prec-div
- PASS2_CFLAGS, PASS2_LDFLAGS
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
- -prof-use
- PASS2_CFLAGS, PASS2_LDFLAGS
-
Instructs the compiler to produce a profile-optimized
executable and merges available dynamic information (.dyn)
files into a pgopti.dpi file. If you perform multiple
executions of the instrumented program, -prof-use merges
the dynamic information files again and overwrites the
previous pgopti.dpi file.
Without any other options, the current directory is
searched for .dyn files
-
-
- -auto-ilp32
- COPTIMIZE
-
This option instructs the compiler to analyze and transform the program so that
64-bit pointers are shrunk to 32-bit pointers, and 64-bit longs (on Linux) are
shrunk into 32-bit longs wherever it is legal and safe to do so.
In order for this option to be effective the compiler must be able to optimize using
the -ipo/-Qipo option and must be able to analyze all library/external calls the program makes.
This option requires that the size of the program executable never exceeds 2^32 bytes and all
data values can be represented within 32 bits. If the program can run correctly in a 32-bit system,
these requirements are implicitly satisfied. If the program violates these size restrictions,
unpredictable behavior might occur.
-
-
- -xSSE4.2
- OPTIMIZE
-
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.
-
-
- -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.
- Includes:
-
- -no-prec-div
- OPTIMIZE
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
-
-
- -parallel
- Yes
- COPTIMIZE
-
Tells the auto-parallelizer to generate multithreaded code for loops that can be safely executed in parallel.
To use this option, you must also specify option O2 or O3. The default numbers of threads spawned is equal to
the number of processors detected in the system where the binary is compiled. Can be changed by setting the
environment variable OMP_NUM_THREADS
-
- -xSSE4.2
- PASS2_CXXFLAGS, PASS2_LDFLAGS
-
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.
-
-
-
- -O3
- PASS2_CXXFLAGS, PASS2_LDFLAGS
-
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.
- Includes:
-
- -no-prec-div
- PASS2_CXXFLAGS, PASS2_LDFLAGS
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
- -prof-use
- PASS2_CXXFLAGS, PASS2_LDFLAGS
-
Instructs the compiler to produce a profile-optimized
executable and merges available dynamic information (.dyn)
files into a pgopti.dpi file. If you perform multiple
executions of the instrumented program, -prof-use merges
the dynamic information files again and overwrites the
previous pgopti.dpi file.
Without any other options, the current directory is
searched for .dyn files
-
-
- -auto-ilp32
- CXXOPTIMIZE
-
This option instructs the compiler to analyze and transform the program so that
64-bit pointers are shrunk to 32-bit pointers, and 64-bit longs (on Linux) are
shrunk into 32-bit longs wherever it is legal and safe to do so.
In order for this option to be effective the compiler must be able to optimize using
the -ipo/-Qipo option and must be able to analyze all library/external calls the program makes.
This option requires that the size of the program executable never exceeds 2^32 bytes and all
data values can be represented within 32 bits. If the program can run correctly in a 32-bit system,
these requirements are implicitly satisfied. If the program violates these size restrictions,
unpredictable behavior might occur.
-
- -xSSE4.2
- PASS2_CXXFLAGS, PASS2_LDFLAGS
-
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.
-
-
-
- -O3
- PASS2_CXXFLAGS, PASS2_LDFLAGS
-
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.
- Includes:
-
- -no-prec-div
- PASS2_CXXFLAGS, PASS2_LDFLAGS
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
- -prof-use
- PASS2_CXXFLAGS, PASS2_LDFLAGS
-
Instructs the compiler to produce a profile-optimized
executable and merges available dynamic information (.dyn)
files into a pgopti.dpi file. If you perform multiple
executions of the instrumented program, -prof-use merges
the dynamic information files again and overwrites the
previous pgopti.dpi file.
Without any other options, the current directory is
searched for .dyn files
-
-
-
-
- -xSSE4.2
- OPTIMIZE
-
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.
-
-
- -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.
- Includes:
-
- -no-prec-div
- OPTIMIZE
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
-
- -parallel
- Yes
- OPTIMIZE
-
Tells the auto-parallelizer to generate multithreaded code for loops that can be safely executed in parallel.
To use this option, you must also specify option O2 or O3. The default numbers of threads spawned is equal to
the number of processors detected in the system where the binary is compiled. Can be changed by setting the
environment variable OMP_NUM_THREADS
-
-
- -xSSE4.2
- PASS2_FFLAGS, PASS2_LDFLAGS
-
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.
-
-
-
- -O3
- PASS2_FFLAGS, PASS2_LDFLAGS
-
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.
- Includes:
-
- -no-prec-div
- PASS2_FFLAGS, PASS2_LDFLAGS
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
- -prof-use
- PASS2_FFLAGS, PASS2_LDFLAGS
-
Instructs the compiler to produce a profile-optimized
executable and merges available dynamic information (.dyn)
files into a pgopti.dpi file. If you perform multiple
executions of the instrumented program, -prof-use merges
the dynamic information files again and overwrites the
previous pgopti.dpi file.
Without any other options, the current directory is
searched for .dyn files
-
-
- -inline-level=0
- OPTIMIZE
-
Specifies the level of inline function expansion.
0 - Disables inlining of user-defined functions. Note that
statement functions are always inlined.
1 - Enables inlining when an inline keyword or an inline
attribute is specified. Also enables inlining according
to the C++ language.
2 - Enables inlining of any function at the compiler's
discretion.
-
-
-
- -xSSE4.2
- PASS2_FFLAGS, PASS2_LDFLAGS
-
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.
-
-
-
- -O3
- PASS2_FFLAGS, PASS2_LDFLAGS
-
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.
- Includes:
-
- -no-prec-div
- PASS2_FFLAGS, PASS2_LDFLAGS
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
- -prof-use
- PASS2_FFLAGS, PASS2_LDFLAGS
-
Instructs the compiler to produce a profile-optimized
executable and merges available dynamic information (.dyn)
files into a pgopti.dpi file. If you perform multiple
executions of the instrumented program, -prof-use merges
the dynamic information files again and overwrites the
previous pgopti.dpi file.
Without any other options, the current directory is
searched for .dyn files
-
-
- -inline-level=0
- OPTIMIZE
-
Specifies the level of inline function expansion.
0 - Disables inlining of user-defined functions. Note that
statement functions are always inlined.
1 - Enables inlining when an inline keyword or an inline
attribute is specified. Also enables inlining according
to the C++ language.
2 - Enables inlining of any function at the compiler's
discretion.
-
-
- -parallel
- Yes
- OPTIMIZE
-
Tells the auto-parallelizer to generate multithreaded code for loops that can be safely executed in parallel.
To use this option, you must also specify option O2 or O3. The default numbers of threads spawned is equal to
the number of processors detected in the system where the binary is compiled. Can be changed by setting the
environment variable OMP_NUM_THREADS
-
-
- -xSSE4.2
- PASS2_FFLAGS, PASS2_LDFLAGS
-
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.
-
-
-
- -O3
- PASS2_FFLAGS, PASS2_LDFLAGS
-
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.
- Includes:
-
- -no-prec-div
- PASS2_FFLAGS, PASS2_LDFLAGS
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
- -prof-use
- PASS2_FFLAGS, PASS2_LDFLAGS
-
Instructs the compiler to produce a profile-optimized
executable and merges available dynamic information (.dyn)
files into a pgopti.dpi file. If you perform multiple
executions of the instrumented program, -prof-use merges
the dynamic information files again and overwrites the
previous pgopti.dpi file.
Without any other options, the current directory is
searched for .dyn files
-
-
- -opt-malloc-options=3
- OPTIMIZE
-
The compiler adds setup code in the C/C++/Fortran main function to enable optimal malloc algorithms:
- n=0: Default, no changes to the malloc options. No call to mallopt() is made.
- n=1: M_MMAP_MAX=2 and M_TRIM_THRESHOLD=0x10000000. Call mallopt with the two settings.
- n=2: M_MMAP_MAX=2 and M_TRIM_THRESHOLD=0x40000000. Call mallopt with these two settings.
- n=3: M_MMAP_MAX=0 and M_TRIM_THRESHOLD=-1. Call mallopt with these two settings. This
will cause use of sbrk() calls instead of mmap() calls to get memory from the system.
The two parameters, M_MMAP_MAX and M_TRIM_THRESHOLD, are described below
Function: int mallopt (int param, int value) When calling mallopt, the param argument
specifies the parameter to be set, and value the new value to be set. Possible choices
for param, as defined in malloc.h, are:
- M_TRIM_THRESHOLD This is the minimum size (in bytes) of the top-most, releasable chunk
that will cause sbrk to be called with a negative argument in order to return memory
to the system.
- M_TOP_PAD This parameter determines the amount of extra memory to obtain from the system
when a call to sbrk is required. It also specifies the number of bytes to retain when
shrinking the heap by calling sbrk with a negative argument. This provides the necessary
hysteresis in heap size such that excessive amounts of system calls can be avoided.
- M_MMAP_THRESHOLD All chunks larger than this value are allocated outside the normal heap,
using the mmap system call. This way it is guaranteed that the memory for these chunks
can be returned to the system on free. Note that requests smaller than this threshold
might still be allocated via mmap.
- M_MMAP_MAX The maximum number of chunks to allocate
with mmap. Setting this to zero disables all use of mmap.
-
-
-
-
- -xSSE4.2
- PASS2_CFLAGS, PASS2_FFLAGS, PASS2_LDFLAGS
-
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.
-
-
-
- -O3
- PASS2_CFLAGS, PASS2_FFLAGS, PASS2_LDFLAGS
-
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.
- Includes:
-
- -no-prec-div
- PASS2_CFLAGS, PASS2_FFLAGS, PASS2_LDFLAGS
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
- -prof-use
- PASS2_CFLAGS, PASS2_FFLAGS, PASS2_LDFLAGS
-
Instructs the compiler to produce a profile-optimized
executable and merges available dynamic information (.dyn)
files into a pgopti.dpi file. If you perform multiple
executions of the instrumented program, -prof-use merges
the dynamic information files again and overwrites the
previous pgopti.dpi file.
Without any other options, the current directory is
searched for .dyn files
-
-
- -auto-ilp32
- COPTIMIZE
-
This option instructs the compiler to analyze and transform the program so that
64-bit pointers are shrunk to 32-bit pointers, and 64-bit longs (on Linux) are
shrunk into 32-bit longs wherever it is legal and safe to do so.
In order for this option to be effective the compiler must be able to optimize using
the -ipo/-Qipo option and must be able to analyze all library/external calls the program makes.
This option requires that the size of the program executable never exceeds 2^32 bytes and all
data values can be represented within 32 bits. If the program can run correctly in a 32-bit system,
these requirements are implicitly satisfied. If the program violates these size restrictions,
unpredictable behavior might occur.
-
-
- -xSSE4.2
- OPTIMIZE
-
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.
-
-
- -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.
- Includes:
-
- -no-prec-div
- OPTIMIZE
-
(disable/enable[default] -prec-div)
-no-prec-div 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.
This will enable the default -prec-div and the result will be more accurate,
with some loss of performance.
-
- -auto-ilp32
- COPTIMIZE
-
This option instructs the compiler to analyze and transform the program so that
64-bit pointers are shrunk to 32-bit pointers, and 64-bit longs (on Linux) are
shrunk into 32-bit longs wherever it is legal and safe to do so.
In order for this option to be effective the compiler must be able to optimize using
the -ipo/-Qipo option and must be able to analyze all library/external calls the program makes.
This option requires that the size of the program executable never exceeds 2^32 bytes and all
data values can be represented within 32 bits. If the program can run correctly in a 32-bit system,
these requirements are implicitly satisfied. If the program violates these size restrictions,
unpredictable behavior might occur.
-
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.
-
- -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
- 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.
-O1 sets the following options:
-funroll-loops0, -fno-builtin, -mno-ieee-fp, -fomit-framepointer, -ffunction-sections, -ftz
- Includes:
-
-
-
-
-
-
Platform settings
One or more of the following settings may have been set. If so, the "General Notes" section of the
report will say so; and you can read below to find out more about what these settings mean.
KMP_STACKSIZE
Specify stack size to be allocated for each thread.
KMP_AFFINITY
KMP_AFFINITY = < physical | logical >, starting-core-id
specifies the static mapping of user threads to physical cores. For example,
if you have a system configured with 8 cores, OMP_NUM_THREADS=8 and
KMP_AFFINITY=physical,0 then thread 0 will mapped to core 0, thread 1 will be mapped to core 1, and
so on in a round-robin fashion.
KMP_AFFINITY = granularity=fine,scatter
The value for the environment variable KMP_AFFINITY affects how the threads from an auto-parallelized program are scheduled across processors.
Specifying granularity=fine selects the finest granularity level, causes each OpenMP thread to be bound to a single thread context.
This ensures that there is only one thread per core on cores supporting HyperThreading Technology
Specifying scatter distributes the threads as evenly as possible across the entire system.
Hence a combination of these two options, will spread the threads evenly across sockets, with one thread per physical core.
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 -openmp and -parallel (Linux and Mac OS X) or /Qopenmp and /Qparallel (Windows).
Example syntax on a Linux system with 8 cores:
export OMP_NUM_THREADS=8
Server Class:
This BIOS option sets "Hardware Prefetcher", "Adjacent Cache Line Prefetch",
"L1 Data Prefetcher" and "Data Reuse Optimization". This default setting is "HPC".
If set to "HPC", each BIOS option set as follows:
- Hardware Prefetcher: Enabled
- Adjacent Cache Line Prefetch: Enabled
- L1 Data Prefetcher: Enabled
- Data Reuse Optimization: Enabled.
If set to "Enterprise", each BIOS option set as follows:
- Hardware Prefetcher: Disabled
- Adjacent Cache Line Prefetch: Disabled
- L1 Data Prefetcher: Disabled
- Data Reuse Optimization: Enabled.
If set to "Custom", it is possible to set each BIOS option which are initialized to their default setting.
Hardware Prefetcher:
This BIOS option allows the enabling/disabling of a processor mechanism to
prefetch data into the cache according to a pattern-recognition algorithm.
This default setting is "Enabled".
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.
Adjacent Cache Line Prefetch:
This BIOS option allows the enabling/disabling of a processor mechanism to
fetch the adjacent cache line within a 128-byte sector that contains
the data needed due to a cache line miss.
This default setting is "Enabled".
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.
L1 Data Prefetcher:
This BIOS option allows enabling/disabling the function of Data Cache Unit (DCU) Streamer prefetcher.
This default setting is "Enabled".
If this option sets to "Enabled", when the DCU Streamer prefetcher detects multiple loads
from the same line done within a time limit, it prefetches the next line
into the L1 data cache.
Data Reuse Optimization:
Enabling this BIOS option reduces the frequency of L3 cache updates from L1.
This default setting is "Enabled".
This may improve performance by reducing the internal bandwidth consumed by constantly updating L1 cache lines in L3.
Since this results in more fetches to main memory,
setting this option to Disabled may improve
performance in some cases. Users should only disable this option
after performing application benchmarking to verify improved
performance in their environment.
Performance/Watt:
This BIOS option sets the turbo boost engagement after the maximum power state (P0).
If set to Traditional this will be less than 2 seconds to provide maximum performance,
otherwise P0 restained for more than 2 seconds. This setting is able to
set to "Traditional" or "Power Optimized" in BIOS. This default setting is "Power Optimized".
FSB High Bandwidth Optimization:
Enabling this option allows the chipset to defer memory transactions and process them out of order for optimal performance.
Hyper-Threading Technology:
Disabling Intel's Hyper-Threading Technology reduces the number of threads per
core to 1. The default is Enabled; in this case each core provides additional
resources for executing up to 2 threads in parallel.
Patrol Scrubbing:
This is a background activity initiated by the processor to seek out and fix memory errors. Patrol Scrub scans all of
memory doing simulated "READs" while checking for ECC errors. If any ECC errors are detected during this process,
they are logged as Patrol errors. Correctable errors are corrected and written back into memory. This mode is able to
set to "Enable" or "Disable" in BIOS.
Memory Voltage:
If set to "Normal" the system supplies 1.5V in memory,
otherwise the system supplies 1.35V in memory. This setting is able to
set to "Low" or "Normal" in BIOS. This default setting is "Low".
NUMA configuration:
This BIOS option allows enabling/disabling the support of Non-Uniform Memory Access (NUMA).
In NUMA mode, physical memory addresses are divided between nodes at a large grain and resource allocation tables describing this division are presented to the operating system.
For example, on a two-node system, if both nodes are configured with 6GB of memory, physical memory addresses 0 - 6GB-1 map to one node and addresses 6GB-12GB-1 map to the other node.
To make use of this, the operating system needs to be NUMA-aware and can then try to optimize access to the processor's local memory.
In Non-NUMA mode (NUMA configuration set to disabled), the memory is interleaved
across the CPUs.
Non-NUMA mode may lead to more balanced but generally reduced performance for bandwidth-sensitive applications.
ulimit -s <n>
Sets the stack size to n kbytes, or unlimited to allow the stack size
to grow without limit.
submit= MYMASK=`printf '0x%x' $((1<<$SPECCOPYNUM))`; /usr/bin/taskset $MYMASK $command
When running multiple copies of benchmarks, the SPEC config file feature
submit is sometimes used to cause individual jobs to be bound to
specific processors. This specific submit command is used for Linux.
The description of the elements of the command are:
- /usr/bin/taskset [options] [mask] [pid | command [arg] ... ]:
taskset is used to set or retrieve the CPU affinity of a running
process given its PID or to launch a new COMMAND with a given CPU
affinity. The CPU affinity is represented as a bitmask, with the
lowest order bit corresponding to the first logical CPU and highest
order bit corresponding to the last logical CPU. When the taskset
returns, it is guaranteed that the given program has been scheduled
to a legal CPU.
The default behavior of taskset is to run a new command with a
given affinity mask:
taskset [mask] [command] [arguments]
- $MYMASK: The bitmask (in hexadecimal) corresponding to a specific
SPECCOPYNUM. For example, $MYMASK value for the first copy of a
rate run will be 0x00000001, for the second copy of the rate will
be 0x00000002 etc. Thus, the first copy of the rate run will have a
CPU affinity of CPU0, the second copy will have the affinity CPU1
etc.
- $command: Program to be started, in this case, the benchmark instance
to be started.
Using numactl to bind processes and memory to cores
For multi-copy runs or single copy runs on systems with multiple sockets, it is advantageous to bind a process to a particular core. Otherwise, the OS may arbitrarily move your process from one core to another. This can affect performance. To help, SPEC allows the use of a "submit" command where users can specify a utility to use to bind processes. We have found the utility 'numactl' to be the best choice.
numactl runs processes with a specific NUMA scheduling or memory placement policy. The policy is set for a command and inherited by all of its children. The numactl flag "--physcpubind" specifies which core(s) to bind the process. "-l" instructs numactl to keep a process memory on the local node while "-m" specifies which node(s) to place a process memory. For full details on using numactl, please refer to your Linux documentation, 'man numactl'
submit= $[top]/mysubmit.pl $SPECCOPYNUM "$command"
On Xeon 74xx series processors, some benchmarks at peak will run n/2 copies on a system with n logical processors.
The mysubmit.pl script assigns each copy in such a way that no two copies will share an L2 cache, for optimal performance.
The script looks in /proc/cpuinfo to come up with the list of cores that will satisfy this requirement.
The source code is shown below.
Source
******************************************************************************************************
#!/usr/bin/perl
use strict;
use Cwd;
# The order in which we want copies to be bound to cores
# Copies: 0, 1, 2, 3
# Cores: 0, 1, 3, 6
my $rundir = getcwd;
my $copynum = shift @ARGV;
my $i;
my $j;
my $tag;
my $num;
my $core;
my $numofcores;
my @proc;
my @cores;
open(INPUT, "/proc/cpuinfo") or
die "can't open /proc/cpuinfo\n";
#open(OUTPUT, "STDOUT");
# proc[i][0] = logical processor ID
# proc[i][1] = physical processor ID
# proc[i][2] = core ID
$i = 0;
$numofcores = 0;
while(<INPUT>)
{
chop;
($tag, $num) = split(/\s+:\s+/, $_);
if ($tag eq "processor") {
$proc[$i][0] = $num;
}
if ($tag eq "physical id") {
$proc[$i][1] = $num;
}
if ($tag eq "core id") {
$proc[$i][2] = $num;
$i++;
$numofcores++;
}
}
$i = 0;
$j = 0;
for $core (0, 4, 2, 1, 5, 3) {
while ($i < $numofcores) {
if ($proc[$i][2] == $core) {
$cores[$j] = $proc[$i][0];
$j++;
}
$i++;
}
$i=0;
}
open RUNCOMMAND, "> runcommand" or die "failed to create run file";
print RUNCOMMAND "cd $rundir\n";
print RUNCOMMAND "@ARGV\n";
close RUNCOMMAND;
system 'taskset', '-c', $cores[$copynum], 'sh', "$rundir/runcommand";
For questions about the meanings of these flags, please contact the tester.
For other inquiries, please contact webmaster@spec.org
Copyright 2006-2014 Standard Performance Evaluation Corporation
Tested with SPEC CPU2006 v1.1.
Report generated on Thu Jul 24 00:41:10 2014 by SPEC CPU2006 flags formatter v6906.
![[benchmark]](http://www.spec.org/auto/cpu2006/flags/benchmark.png)