MPI2007 Flag Description
SGI SGI Altix 4700 Bandwidth System (Itanium 2 Processor 9040 1.6GHz/18M)

Base Optimization Flags

C benchmarks

• • -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 Intel Itanium processors, the O3 option enables optimizations for technical computing applications (loop-intensive code):
    loop optimizations and data prefetch. 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:
    • -O2
      • -O1
        • -unrolln
        • -builtin
        • -mno-ieee-fp
        • -fomit-frame-pointer
        • -ffunction-sections
• • -ipo
  • 
  • COPTIMIZE

  • Multi-file ip optimizations that includes:
    - inline function expansion
    - interprocedural constant propogation
    - dead code elimination
    - propagation of function characteristics
    - passing arguments in registers
    - loop-invariant code motion

• • -IPF-fp-relaxed
  • 
  • COPTIMIZE

  • Enables use of faster but slightly less accurate code sequences for math functions, including sqrt, reciprocal sqrt, divide and reciprocal. When compared to strict IEEE* precision, this option slightly reduces the accuracy of floating-point calculations performed by these functions, usually limited to the least significant digit. This option also performs reassociation transformations, which can alter the order of operations, over a larger scope. The increased reasssociation enables generation of more optimal sequences of floating-point multiply-add instructions than not using this option. Note that use of floating-point multiply-add can cause programs to produce different numerical results due to changes in rounding.

• • -lmpi
  • 
  • EXTRA_LIBS

  • MPI library.

C++ benchmarks

126.lammps

• • -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 Intel Itanium processors, the O3 option enables optimizations for technical computing applications (loop-intensive code):
    loop optimizations and data prefetch. 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:
    • -O2
      • -O1
        • -unrolln
        • -builtin
        • -mno-ieee-fp
        • -fomit-frame-pointer
        • -ffunction-sections
• • -ipo
  • 
  • CXXOPTIMIZE

  • Multi-file ip optimizations that includes:
    - inline function expansion
    - interprocedural constant propogation
    - dead code elimination
    - propagation of function characteristics
    - passing arguments in registers
    - loop-invariant code motion

• • -IPF-fp-relaxed
  • 
  • CXXOPTIMIZE

  • Enables use of faster but slightly less accurate code sequences for math functions, including sqrt, reciprocal sqrt, divide and reciprocal. When compared to strict IEEE* precision, this option slightly reduces the accuracy of floating-point calculations performed by these functions, usually limited to the least significant digit. This option also performs reassociation transformations, which can alter the order of operations, over a larger scope. The increased reasssociation enables generation of more optimal sequences of floating-point multiply-add instructions than not using this option. Note that use of floating-point multiply-add can cause programs to produce different numerical results due to changes in rounding.

• • -ansi-alias
  • 
  • intel_icc,intel_icpc
  • CXXOPTIMIZE

  • Tells the compiler to assume the program does adhere to the rules defined in the ISO C Standard. The default is to not assume such adherence. If your C/C++ program adheres to these rules, then -ansi-alias will allow the compiler to optimize more aggressively. If it doesn't adhere to these rules, then assuming so can cause the compiler to generate incorrect code.

• • -lmpi
  • 
  • EXTRA_LIBS

  • MPI library.

Fortran benchmarks

• • -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 Intel Itanium processors, the O3 option enables optimizations for technical computing applications (loop-intensive code):
    loop optimizations and data prefetch. 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:
    • -O2
      • -O1
        • -unrolln
        • -builtin
        • -mno-ieee-fp
        • -fomit-frame-pointer
        • -ffunction-sections
• • -ipo
  • 
  • FOPTIMIZE

  • Multi-file ip optimizations that includes:
    - inline function expansion
    - interprocedural constant propogation
    - dead code elimination
    - propagation of function characteristics
    - passing arguments in registers
    - loop-invariant code motion

• • -IPF-fp-relaxed
  • 
  • FOPTIMIZE

  • Enables use of faster but slightly less accurate code sequences for math functions, including sqrt, reciprocal sqrt, divide and reciprocal. When compared to strict IEEE* precision, this option slightly reduces the accuracy of floating-point calculations performed by these functions, usually limited to the least significant digit. This option also performs reassociation transformations, which can alter the order of operations, over a larger scope. The increased reasssociation enables generation of more optimal sequences of floating-point multiply-add instructions than not using this option. Note that use of floating-point multiply-add can cause programs to produce different numerical results due to changes in rounding.

• • -lmpi
  • 
  • EXTRA_LIBS

  • MPI library.

Benchmarks using both Fortran and C

• • -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 Intel Itanium processors, the O3 option enables optimizations for technical computing applications (loop-intensive code):
    loop optimizations and data prefetch. 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:
    • -O2
      • -O1
        • -unrolln
        • -builtin
        • -mno-ieee-fp
        • -fomit-frame-pointer
        • -ffunction-sections
• • -ipo
  • 
  • COPTIMIZE, FOPTIMIZE

  • Multi-file ip optimizations that includes:
    - inline function expansion
    - interprocedural constant propogation
    - dead code elimination
    - propagation of function characteristics
    - passing arguments in registers
    - loop-invariant code motion

• • -IPF-fp-relaxed
  • 
  • COPTIMIZE, FOPTIMIZE

  • Enables use of faster but slightly less accurate code sequences for math functions, including sqrt, reciprocal sqrt, divide and reciprocal. When compared to strict IEEE* precision, this option slightly reduces the accuracy of floating-point calculations performed by these functions, usually limited to the least significant digit. This option also performs reassociation transformations, which can alter the order of operations, over a larger scope. The increased reasssociation enables generation of more optimal sequences of floating-point multiply-add instructions than not using this option. Note that use of floating-point multiply-add can cause programs to produce different numerical results due to changes in rounding.

• • -lmpi
  • 
  • EXTRA_LIBS

  • MPI library.