ULSTRD Bug in BINARY open/close read

[langevin-usgs]

From Mike Toews:

Hi Christian,

While investigating flopy's t052 that demonstrates using an unformatted (a.k.a. BINARY) open/close file for the WEL package, I found a Fortran bug in ULSTRD.

When compiled without optimisation, there is often no bug as all variables (e.g. JAUX) are initialised as zero, and the two well stress rates are correctly listed as -1000. and -500.0.

Gfortran has a silent form of this bug, where all stress rates are printed as -0.0, and well budget terms are also printed as zero. It seems that all stress rates were multiplied by zero on line 378 of util7.f, as SFAC=1. (at top of subroutine).

Intel with "-g -O0 -traceback -check all" compiler flags is a bit more explicit:

$ mf2005 t1.nam
                                  MODFLOW-2005
    U.S. GEOLOGICAL SURVEY MODULAR FINITE-DIFFERENCE GROUND-WATER FLOW MODEL
                             Version 1.12.00 2/3/2017

Using NAME file: t1.nam

Run start date and time (yyyy/mm/dd hh:mm:ss): 2018/08/30 14:48:59

forrtl: severe (194): Run-Time Check Failure. The variable 'ulstrd_$JAUX' is being used in 'utl7.f(378,18)' without being defined

Image              PC                Routine            Line        Source

mf2005             0000000001D876DD  ulstrd_                   378  utl7.f

mf2005             00000000019BA3EC  gwf2wel7rp_               177  gwf2wel7.f

mf2005             0000000001B28FCC  MAIN__                    156  mf2005.f

mf2005             000000000040569E  Unknown               Unknown  Unknown

libc-2.12.so       0000003A2401ED1D  __libc_start_main     Unknown  Unknown

mf2005             00000000004055A9  Unknown               Unknown  Unknown

Indeed JAUX is only initialised for the formatted read. One suggestion is to move this initialization at the top and/or only scale the fields for the ascii file. I've done both in this patch:

--- utl7.f.orig

+++ utl7.f.mod

@@ -222,6 +222,7 @@

       IN=INPACK

       ICLOSE=0

       IBINARY=0

+      JAUX=0

       READ(IN,'(A)') LINE

       SFAC=1.

       LLOC=1

@@ -323,7 +324,6 @@

C

C5------CHECK FOR AUXILIARY VARIABLE "AUXSFAC" AND STORE LOCATION

C5------READ AN ASCII LIST

-        JAUX = 0

         DO 230 JJ=1,NAUX

           IF(CAUX(JJ) .EQ. "AUXSFAC") THEN

             JAUX=JJ+NREAD1

@@ -373,10 +373,12 @@

       J=RLIST(3,II)

C

C6A------Scale fields ISCLOC1-ISCLOC2 by SFAC and AUXSFAC (if present)

+      IF (IBINARY.NE.1) THEN

       DO 204 ILOC=ISCLOC1,ISCLOC2

         RLIST(ILOC,II)=RLIST(ILOC,II)*SFAC

         IF (JAUX .NE. 0) RLIST(ILOC,II)=RLIST(ILOC,II)*RLIST(JAUX,II)

204   CONTINUE

+      END IF

C

C6C-----Write the values that were read if IPRFLG is 1.

       NN=II-LSTBEG+1

Cheers,