OMP2012 Flag Description
Hewlett Packard Enterprise Apollo 70 (Marvell ThunderX2 CN9980 v2.1, 2.20GHz)

Base Optimization Flags

C benchmarks

• • -O3
  • 
  • COPTIMIZE

  • -O3 is a higher optimization for performance compared to -O2. This optimization level enables optimizations that require significant compile-time analysis and resources, and changes the heuristics for optimizations compared to -O2. -O3 instructs the compiler to optimize for the performance of generated code and disregard the size of the generated code, which might result in an increased code size. It also degrades the debug experience compared to -O2.

    The differences when using -O3 as compared to -O2 are: The threshold at which the compiler believes that it is profitable to inline a call site increases. The amount of loop unrolling that is performed is increased. More aggressive instruction optimizations are enabled late in the compiler pipeline.

• • -ffast-math
  • 
  • COPTIMIZE

  • Allow aggressive, lossy floating-point optimizations.

• • -fopenmp
  • 
  • COPTIMIZE

  • Enable handling of OpenMP directives "#pragma omp" in C/C++ and "!$omp" in Fortran. When -fopenmp is specified, the compiler generates parallel code according to the OpenMP Application Program Interface v4.0 . This option implies -pthread, and thus is only supported on targets that have support for -pthread. -fopenmp implies -fopenmp-simd.

• • -fsigned-char
  • 
  • clang, clangplusplus
  • COPTIMIZE

  • specifies signed char characters. The compiler treats "plain" char declarations as signed char.

• • -mcpu=native
  • 
  • COPTIMIZE

  • -mcpu=native causes the compiler to auto-detect the CPU of the build computer. At present, this feature is only supported on GNU/Linux, and not all architectures are recognized. If the auto-detect is unsuccessful the option has no effect.

C++ benchmarks

• • -O3
  • 
  • CXXOPTIMIZE

  • -O3 is a higher optimization for performance compared to -O2. This optimization level enables optimizations that require significant compile-time analysis and resources, and changes the heuristics for optimizations compared to -O2. -O3 instructs the compiler to optimize for the performance of generated code and disregard the size of the generated code, which might result in an increased code size. It also degrades the debug experience compared to -O2.

    The differences when using -O3 as compared to -O2 are: The threshold at which the compiler believes that it is profitable to inline a call site increases. The amount of loop unrolling that is performed is increased. More aggressive instruction optimizations are enabled late in the compiler pipeline.

• • -ffast-math
  • 
  • CXXOPTIMIZE

  • Allow aggressive, lossy floating-point optimizations.

• • -fopenmp
  • 
  • CXXOPTIMIZE

  • Enable handling of OpenMP directives "#pragma omp" in C/C++ and "!$omp" in Fortran. When -fopenmp is specified, the compiler generates parallel code according to the OpenMP Application Program Interface v4.0 . This option implies -pthread, and thus is only supported on targets that have support for -pthread. -fopenmp implies -fopenmp-simd.

• • -mcpu=native
  • 
  • CXXOPTIMIZE

  • -mcpu=native causes the compiler to auto-detect the CPU of the build computer. At present, this feature is only supported on GNU/Linux, and not all architectures are recognized. If the auto-detect is unsuccessful the option has no effect.

Fortran benchmarks

• • -O3
  • 
  • FOPTIMIZE

  • -O3 is a higher optimization for performance compared to -O2. This optimization level enables optimizations that require significant compile-time analysis and resources, and changes the heuristics for optimizations compared to -O2. -O3 instructs the compiler to optimize for the performance of generated code and disregard the size of the generated code, which might result in an increased code size. It also degrades the debug experience compared to -O2.

    The differences when using -O3 as compared to -O2 are: The threshold at which the compiler believes that it is profitable to inline a call site increases. The amount of loop unrolling that is performed is increased. More aggressive instruction optimizations are enabled late in the compiler pipeline.

• • -ffast-math
  • 
  • FOPTIMIZE

  • Allow aggressive, lossy floating-point optimizations.

• • -fopenmp
  • 
  • FOPTIMIZE

  • Enable handling of OpenMP directives "#pragma omp" in C/C++ and "!$omp" in Fortran. When -fopenmp is specified, the compiler generates parallel code according to the OpenMP Application Program Interface v4.0 . This option implies -pthread, and thus is only supported on targets that have support for -pthread. -fopenmp implies -fopenmp-simd.

• • -mcpu=native
  • 
  • FOPTIMIZE

  • -mcpu=native causes the compiler to auto-detect the CPU of the build computer. At present, this feature is only supported on GNU/Linux, and not all architectures are recognized. If the auto-detect is unsuccessful the option has no effect.