Error on installation

Dear Jessica,

Let me first give a general reply to this frequent question, and then give you very specific instructions for using gfortran.

General:

This issue is described in the read-me file that came with TOUGH2.

Subroutine SECOND (see file t2cg22.f) is supposed to return the CPU time. It calls a system function that - unfortunately - is platform specific and/or compiler dependent. Typical system functions include etime(), second(), cpu_time(), mclock(), and timer(). You have to check your FORTRAN language reference to see what the CPU timing function is for your system, and what arguments it takes. Then customize subroutine SECOND accordingly. Since CPU time is not an essential part of a TOUGH simulation, you may also decide to return zero or simply comment it (and the few "CALL SECOND) out.

Specific Instructions for gfortran

In gfortran, SECOND is itself the intrinsic function that returns the elapsed CPU time. However, it requires a REAL*4 argument (not the REAL*8 variable used in TOUGH2; this is what your error message indicates). The easiest way to make it all work is therefore to:

(1) Replace all "CALL SECOND" with "CALL CPUSEC"

(2) In t2cg22.f, replace SUBROUTINE SECOND with the following:

**********************************************************************
      SUBROUTINE CPUSEC(SS)
**********************************************************************
      REAL*8  SS
      REAL*4  S
      S=SECOND()
      SS=S
      END

Hope this helps!

Stefan