# 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.

Linux

It sets the following options:

-ipo, -O3, -no-prec-div,-static, -fp-model fast=2, and -xHost

macOS

It sets the following options:

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

Windows

It sets the following options:

/O3, /Qipo, /Qprec-div-, /fp:fast=2, and /QxHost

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:

Linux

If you specify option -fast -xSSE3, option -xSSE3 takes effect. However, if you specify -xSSE3 -fast, option -xHost takes effect.

Windows

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.

### Note

This option only applies to host compilation. When offloading is enabled, it does not impact device-specific compilation. Offloading can only be enabled when using ifx.

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