hpc2021 Flag Description

Base Optimization Flags

C benchmarks

• • -Ofast
  • 
  • mpicc, mpicxx, mpifort, mpiicc, mpiicpc, mpiifort, mpiicx, mpiicpx, mpiifx, icx, icpx, ifx
  • OPTIMIZE

  • Enable -O3 -no-prec-div -fp-model fast=2 optimizations.

• • -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

• • -mprefer-vector-width=512
  • 
  • OPTIMIZE

  • Specifies preferred 512b vector width for auto-vectorization. Defaults to 'none' which allows target specific decisions.

• • -march=common-avx512
  • 
  • OPTIMIZE

  • May generate machine code optimized for processors supporting the AVX-512 instruction set.

• • -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, mpiicx, mpiicpx, mpiifx, icx, icpx, ifx
  • OPTIMIZE

  • Enable -O3 -no-prec-div -fp-model fast=2 optimizations.

• • -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

• • -mprefer-vector-width=512
  • 
  • OPTIMIZE

  • Specifies preferred 512b vector width for auto-vectorization. Defaults to 'none' which allows target specific decisions.

• • -march=common-avx512
  • 
  • OPTIMIZE

  • May generate machine code optimized for processors supporting the AVX-512 instruction set.

• • -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, mpiicx, mpiicpx, mpiifx, icx, icpx, ifx
  • OPTIMIZE

  • Enable -O3 -no-prec-div -fp-model fast=2 optimizations.

• • -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

• • -mprefer-vector-width=512
  • 
  • OPTIMIZE

  • Specifies preferred 512b vector width for auto-vectorization. Defaults to 'none' which allows target specific decisions.

• • -march=common-avx512
  • 
  • OPTIMIZE

  • May generate machine code optimized for processors supporting the AVX-512 instruction set.

• • -nostandard-realloc-lhs
  • 
  • FOPTIMIZE

  • Option standard-realloc-lhs (the default), tells the compiler that when the left-hand side of an assignment is an allocatable object, it should be reallocated to the shape of the right-hand side of the assignment before the assignment occurs. This is the current Fortran Standard definition. This feature may cause extra overhead at run time. This option has the same effect as option assume realloc_lhs.

    If you specify nostandard-realloc-lhs, the compiler uses the old Fortran 2003 rules when interpreting assignment statements. The left-hand side is assumed to be allocated with the correct shape to hold the right-hand side. If it is not, incorrect behavior will occur. This option has the same effect as option assume norealloc_lhs.

• • -align array64byte
  • 
  • FOPTIMIZE

  • The align toggle changes how data elements are aligned. Variables and arrays are analyzed and memory layout can be altered. Specifying array64byte will look for opportunities to transform and reailgn arrays to 64byte boundaries.