UNROLL directive (The GNU Fortran Compiler)

#### 6.2.2 `UNROLL` directive ¶

The syntax of the directive is

`!GCC$ unroll N`

You can use this directive to control how many times a loop should be unrolled. It must be placed immediately before a `DO` loop and applies only to the loop that follows. N is an integer constant specifying the unrolling factor. The values of 0 and 1 block any unrolling of the loop.

For `DO CONCURRENT` constructs the unrolling specification applies only to the first loop control variable.