The C$PRAGMA SUN UNROLL=n directive instructs the compiler to unroll the following loop n times during its optimization pass. (The compiler will unroll a loop only when its analysis regards such unrolling as appropriate.)
n is a positive integer. The choices are:
If n=1, the optimizer may not unroll any loops.
If n>1, the optimizer may unroll loops n times.
If any loops are actually unrolled, the executable file becomes larger. For further information, see the Fortran Programming Guide chapter on performance and optimization.
Example - unrolling loops two times:
C$PRAGMA SUN UNROLL=2