hpc2021 Flag Description

Base Optimization Flags

C benchmarks

• • -Ofast
  • 
  • mpicc, mpicxx, mpifort, mpiicc, mpiicpc, mpiifort
  • OPTIMIZE

  • Chooses generally optimal flags for the target platform.

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

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

    When you specify -no-prec-div along with some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.

    However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, do not use -no-prec-div which will enable the default -prec-div and the result is more accurate, with some loss of performance.

• • -xCORE-AVX512
  • 
  • OPTIMIZE

  • Code is optimized for Intel(R) processors with support for AVX instructions. May generate Intel® AVX-12 Foundation instructions,Intel® AVX-512 Conflict Detectio instructions, Intel® AVX-512 Doubleword and Quadword instructions, Intel® AVX-51 Byte and Word instructions, Intel® AVX-512 Vector Length extensions, Intel® AVX2,VX SSE4.2, SSE4.1, SSSE3, SSE3, SSE2 and SSE instructions for Intel® processors. Optimizes for a future Intel® processor. Available in compiler version 15 update 1 and later.

• • -ipo
  • 
  • OPTIMIZE

  • 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

• • -qopenmp
  • 
  • mpicc, mpicxx, mpifort, mpiicc, mpiicpc, mpiifort
  • OPTIMIZE

  • Enable OpenMP compilation for hpc2021.

• • -ansi-alias
  • 
  • COPTIMIZE

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

C++ benchmarks

• • -Ofast
  • 
  • mpicc, mpicxx, mpifort, mpiicc, mpiicpc, mpiifort
  • OPTIMIZE

  • Chooses generally optimal flags for the target platform.

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

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

    When you specify -no-prec-div along with some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.

    However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, do not use -no-prec-div which will enable the default -prec-div and the result is more accurate, with some loss of performance.

• • -xCORE-AVX512
  • 
  • OPTIMIZE

  • Code is optimized for Intel(R) processors with support for AVX instructions. May generate Intel® AVX-12 Foundation instructions,Intel® AVX-512 Conflict Detectio instructions, Intel® AVX-512 Doubleword and Quadword instructions, Intel® AVX-51 Byte and Word instructions, Intel® AVX-512 Vector Length extensions, Intel® AVX2,VX SSE4.2, SSE4.1, SSSE3, SSE3, SSE2 and SSE instructions for Intel® processors. Optimizes for a future Intel® processor. Available in compiler version 15 update 1 and later.

• • -ipo
  • 
  • OPTIMIZE

  • 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

• • -qopenmp
  • 
  • mpicc, mpicxx, mpifort, mpiicc, mpiicpc, mpiifort
  • OPTIMIZE

  • Enable OpenMP compilation for hpc2021.

• • -ansi-alias
  • 
  • CXXOPTIMIZE

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

Fortran benchmarks

• • -Ofast
  • 
  • mpicc, mpicxx, mpifort, mpiicc, mpiicpc, mpiifort
  • OPTIMIZE

  • Chooses generally optimal flags for the target platform.

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

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

    When you specify -no-prec-div along with some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A * (1/B) to improve the speed of the computation.

    However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, do not use -no-prec-div which will enable the default -prec-div and the result is more accurate, with some loss of performance.

• • -xCORE-AVX512
  • 
  • OPTIMIZE

  • Code is optimized for Intel(R) processors with support for AVX instructions. May generate Intel® AVX-12 Foundation instructions,Intel® AVX-512 Conflict Detectio instructions, Intel® AVX-512 Doubleword and Quadword instructions, Intel® AVX-51 Byte and Word instructions, Intel® AVX-512 Vector Length extensions, Intel® AVX2,VX SSE4.2, SSE4.1, SSSE3, SSE3, SSE2 and SSE instructions for Intel® processors. Optimizes for a future Intel® processor. Available in compiler version 15 update 1 and later.

• • -ipo
  • 
  • OPTIMIZE

  • 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

• • -qopenmp
  • 
  • mpicc, mpicxx, mpifort, mpiicc, mpiicpc, mpiifort
  • OPTIMIZE

  • Enable OpenMP compilation for hpc2021.