The transformation for the toy problem

        subroutine head(x,y) 
          double precision,intent(in) :: x
          double precision,intent(out) :: y
          y=sin(x*x)
        end subroutine

in practice leads to a slightly more complex representation in code which is given below. It shows colored sections for

• function value
  
• partial computation
• elimination operations and saxpy call for Jacobian entry
  

Note that the generated code contains additional temporaries due to the fact that currenty we do not have any interprocedural alias analysis. Without an interprocedural alias analysis one has to conservatively assume that there may be a call head(w,w), i.e. the formal parameters x and y may be aliased. This requires additional temporary variables in the code to properly handle potential overwrites.

C ***********************************************************
C Fortran file translated from WHIRL Mon Sep 13 04:52:02 2004
C ***********************************************************
C ***********************************************************

      SUBROUTINE head(X, Y)
      use w2f__types
      use active_module
      IMPLICIT NONE
C
C     **** Global Variables ****
C
      REAL(w2f__8) OpenAD_Symbol_0
      REAL(w2f__8) OpenAD_Symbol_1
      REAL(w2f__8) OpenAD_Symbol_2
      REAL(w2f__8) OpenAD_Symbol_3
      REAL(w2f__8) OpenAD_Symbol_4
      REAL(w2f__8) OpenAD_Symbol_5
      type(active) :: OpenAD_Symbol_6
C
C     **** Parameters and Result ****
C
      type(active) :: X
      INTENT(IN)  X
      type(active) :: Y
      INTENT(OUT)  Y
C
C     **** statements ****
C
      OpenAD_Symbol_0 = (X%v*X%v)
      OpenAD_Symbol_4 = SIN(OpenAD_Symbol_0)
      OpenAD_Symbol_2 = X%v
      OpenAD_Symbol_3 = X%v
      OpenAD_Symbol_1 = COS(OpenAD_Symbol_0)
      Y%v = OpenAD_Symbol_4
      OpenAD_Symbol_5 = ((OpenAD_Symbol_3 + OpenAD_Symbol_2) *
     >  OpenAD_Symbol_1)
      CALL setderiv(OpenAD_Symbol_6,X)
      CALL sax(OpenAD_Symbol_5,OpenAD_Symbol_6,Y)
      RETURN
      END SUBROUTINE