READONLY(varlist)

The READONLY(varlist) qualifier specifies that all scalars and arrays in the list varlist are read-only for the DOALL loop. Read-only scalars and arrays are a special class of shared scalars and arrays that are not modified in any iteration of the DOALL loop. Specifying scalars and arrays as READONLY indicates to the compiler that it does not need to use a separate copy of that variable or array for each thread of the DOALL loop.

Example: Specify a read-only variable:

      x = 3
C$PAR DOALL SHARED(x),READONLY(x)
      do i = 1, n
        b(i) = x + 1
      end do

In the preceding example, x is a shared variable, but the compiler can rely on the fact that it will not change over each iteration of the i loop because of its READONLY specification.