automatic

IDE Equivalent

Windows: Data > Local Variable Storage

Linux: None

Mac OS X: None

Architectures

IA-32, Intel® 64, IA-64 architectures

Syntax

Arguments

None

Default

Description

This option places local variables (scalars and arrays of all types), except those declared as SAVE, on the run-time stack. It is as if the variables were declared with the AUTOMATIC attribute.

It does not affect variables that have the SAVE attribute or ALLOCATABLE attribute, or variables that appear in an EQUIVALENCE statement or in a common block.

This option may provide a performance gain for your program, but if your program depends on variables having the same value as the last time the routine was invoked, your program may not function properly.

If you want to cause variables to be placed in static memory, specify option -save (Linux and Mac OS X) or /Qsave (Windows). If you want only scalar variables of certain intrinsic types to be placed on the run-time stack, specify option auto-scalar.

Note

On Windows NT* systems, there is a performance penalty for addressing a stack frame that is too large. This penalty may be incurred with /automatic, /auto, or /Qauto because arrays are allocated on the stack along with scalars. However, with /Qauto-scalar, you would have to have more than 32K bytes of local scalar variables before you incurred the performance penalty. /Qauto-scalar enables the compiler to make better choices about which variables should be kept in registers during program execution.

Alternate Options