OMP2012 Flag Description
Cray Cray XC30 (Intel Xeon E5-2697 v2)

Base Optimization Flags

C benchmarks

• • -ansi-alias
  • 
  • COPTIMIZE

  • Enable/disable(DEFAULT) use of ANSI aliasing rules in optimizations; user asserts that the program adheres to these rules.

• • -qopenmp
  • 
  • COPTIMIZE

  • Enables the parallelizer to generate multi-threaded code based on OpenMP* directives. Option -qopenmp is the replacement option for -openmp, which is deprecated.

• • -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

• • -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. On IA-32 Windows platforms, -O3 sets the following:

    /GF (/Qvc7 and above), /Gf (/Qvc6 and below), and /Ob2

  • Includes:
    • -GF
    • -Gf
    • -Ob_n
    • -O2
      • -Oi-
      • -Gs
      • -Oy
      • -Gy
      • -Os
      • -GF
      • -Gf
      • -Ob_n
      • -Og
      • -O1
        • -unroll_n
        • -Oi-
        • -Op-
        • -Oy
        • -Gy
        • -Os
        • -GF
        • -Gf
        • -Ob_n
        • -Og
• • -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.

• • -no-prec-sqrt
  • 
  • COPTIMIZE
  • (disable/enable[default] -[no-]prec-div)

    -prec-sqrt improves precision of floating-point square root. It has a slight impact on speed. -no-prec-sqrt disables this option and enables optimizations that give slightly less precise results than full IEEE division.

• • -fp-model fast=2
  • 
  • COPTIMIZE

  • enable floating point model variation [no-]except - enable/disable floating point semantics fast[=1|2] - enables more aggressive floating point optimizations precise - allows value-safe optimizations source - enables intermediates in source precision strict - enables -fp-model precise -fp-model except, disables contractions and enables pragma stdc fenv_access double - rounds intermediates in 53-bit (double) precision extended - rounds intermediates in 64-bit (extended) precision

• • -xHost
  • 
  • COPTIMIZE

  • Tells the compiler to generate instructions for the highest instruction set available on the compilation host processor.

C++ benchmarks

• • -ansi-alias
  • 
  • CXXOPTIMIZE

  • Enable/disable(DEFAULT) use of ANSI aliasing rules in optimizations; user asserts that the program adheres to these rules.

• • -qopenmp
  • 
  • CXXOPTIMIZE

  • Enables the parallelizer to generate multi-threaded code based on OpenMP* directives. Option -qopenmp is the replacement option for -openmp, which is deprecated.

• • -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

• • -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:
    • -GF
    • -Gf
    • -Ob_n
    • -O2
      • -Oi-
      • -Gs
      • -Oy
      • -Gy
      • -Os
      • -GF
      • -Gf
      • -Ob_n
      • -Og
      • -O1
        • -unroll_n
        • -Oi-
        • -Op-
        • -Oy
        • -Gy
        • -Os
        • -GF
        • -Gf
        • -Ob_n
        • -Og
• • -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.

• • -no-prec-sqrt
  • 
  • CXXOPTIMIZE
  • (disable/enable[default] -[no-]prec-div)

    -prec-sqrt improves precision of floating-point square root. It has a slight impact on speed. -no-prec-sqrt disables this option and enables optimizations that give slightly less precise results than full IEEE division.

• • -fp-model fast=2
  • 
  • CXXOPTIMIZE

  • enable floating point model variation [no-]except - enable/disable floating point semantics fast[=1|2] - enables more aggressive floating point optimizations precise - allows value-safe optimizations source - enables intermediates in source precision strict - enables -fp-model precise -fp-model except, disables contractions and enables pragma stdc fenv_access double - rounds intermediates in 53-bit (double) precision extended - rounds intermediates in 64-bit (extended) precision

• • -xHost
  • 
  • CXXOPTIMIZE

  • Tells the compiler to generate instructions for the highest instruction set available on the compilation host processor.

Fortran benchmarks

• • -qopenmp
  • 
  • FOPTIMIZE

  • Enables the parallelizer to generate multi-threaded code based on OpenMP* directives. Option -qopenmp is the replacement option for -openmp, which is deprecated.

• • -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

• • -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:
    • -GF
    • -Gf
    • -Ob_n
    • -O2
      • -Oi-
      • -Gs
      • -Oy
      • -Gy
      • -Os
      • -GF
      • -Gf
      • -Ob_n
      • -Og
      • -O1
        • -unroll_n
        • -Oi-
        • -Op-
        • -Oy
        • -Gy
        • -Os
        • -GF
        • -Gf
        • -Ob_n
        • -Og
• • -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.

• • -no-prec-sqrt
  • 
  • FOPTIMIZE
  • (disable/enable[default] -[no-]prec-div)

    -prec-sqrt improves precision of floating-point square root. It has a slight impact on speed. -no-prec-sqrt disables this option and enables optimizations that give slightly less precise results than full IEEE division.

• • -fp-model fast=2
  • 
  • FOPTIMIZE

  • enable floating point model variation [no-]except - enable/disable floating point semantics fast[=1|2] - enables more aggressive floating point optimizations precise - allows value-safe optimizations source - enables intermediates in source precision strict - enables -fp-model precise -fp-model except, disables contractions and enables pragma stdc fenv_access double - rounds intermediates in 53-bit (double) precision extended - rounds intermediates in 64-bit (extended) precision

• • -xHost
  • 
  • FOPTIMIZE

  • Tells the compiler to generate instructions for the highest instruction set available on the compilation host processor.