# Optimization Options

This section contains descriptions for compiler options that pertain to optimization. They are listed in alphabetical order.

Parent topic: Compiler Options

- falias, Oa
  Specifies whether or not a procedure call may have hidden aliases of local variables not supplied as actual arguments.
- fast
  Maximizes speed across the entire program.
- ffnalias, Ow
  Determines whether aliasing is assumed within functions. This feature is only available for ifort.
- foptimize-sibling-calls
  Determines whether the compiler optimizes tail recursive calls. This feature is only available for ifort.
- fprotect-parens, Qprotect-parens
  Determines whether the optimizer honors parentheses when floating-point expressions are evaluated.
- GF
  Enables read-only string-pooling optimization.
- nolib-inline
  Disables inline expansion of standard library or intrinsic functions.
- O
  Specifies the code optimization for applications.
- Od
  Disables all optimizations.
- Ofast
  Sets certain aggressive options to improve the speed of your application.
- Os
  Enables optimizations that do not increase code size; it produces smaller code size than O2.
- Ot
  Enables all speed optimizations.