# fast

Maximizes speed across the entire program.

## Syntax

Linux: | -fast

macOS: | -fast

Windows: | /fast

## Arguments

None

## Default

OFF | The optimizations that maximize speed are not enabled.

## Description

This option maximizes speed across the entire program.

It sets the following options:

- On macOS systems: -ipo, -mdynamic-no-pic,-O3, -no-prec-div,-fp-model fast=2, and -xHost

- On Windows* systems: /O3, /Qipo, /Qprec-div-, /fp:fast=2, and /QxHost

- On Linux* systems: -ipo, -O3, -no-prec-div,-static, -fp-model fast=2, and -xHost

When option fast is specified, you can override the [Q]xHost option setting by specifying a different processor-specific [Q]x option on the command line. However, the last option specified on the command line takes precedence.

For example:

- On Linux* systems, if you specify option -fast -xSSE3, option -xSSE3 takes effect. However, if you specify -xSSE3 -fast, option -xHost takes effect.

- On Windows* systems, if you specify option /fast /QxSSE3, option/QxSSE3 takes effect. However, if you specify /QxSSE3 /fast, option /QxHost takes effect.

For implications on non-Intel processors, refer to the [Q]xHost documentation.

### Note

Option fast sets some aggressive optimizations that may not be appropriate for all applications. The resulting executable may not run on processor types different from the one on which you compile. You should make sure that you understand the individual optimization options that are enabled by option fast.

Product and Performance Information
Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex. Notice revision #20201201

## IDE Equivalent

None

## Alternate Options

None

Parent topic: Optimization Options

## See Also

fp-model, fp compiler option
xHost, QxHost compiler option
x, Qx compiler option