********> bugfix.64
Correction Author: David A. Pearlman
Correction Date: 02/20/96

Programs: GIBBS

Severity: Slight

Problem: 

       An attempt to restart a Gibbs simulation can fail with an 
       "unexpected character" message when one is attempting
       to restart a simulation that ran more than 999,999 MD steps.

       The "unexpected character" error arises from an overflowed field
       in the restart file.  A simple workaround is available (see below).
       Note that this fix trivially modifies the 'restrt' format.

Affects: 

       On most computers, the simulation will immediately halt.
       There is no other effect, because the variable that should appear
       in the overflow field is not subsequently used.

Cause: 

       A variable that contains the accumuated step total was being
       written to (and read from )the restart file in (I6) format. Since the 
       total number of steps may exceed the capacity of this format,
       an error can occur.

Fix:  Make the following changes to file slwadj.f:
------------------------------------------------------------------------------
*** OLD slwadj.f
--- NEW slwadj.f
***************
*** 610,616 ****
  C
  C Read variables for the PRTST2 block:
  C
!           READ(NF,END=200) IONCE4,ISTORC,NSTPSV
            READ(NF,END=200) DSTOT,DETOT,RLM,TIINTS
  C
  C -----------------
--- 610,616 ----
  C
  C Read variables for the PRTST2 block:
  C
!           READ(NF,END=200) IONCE4,ISTORC
            READ(NF,END=200) DSTOT,DETOT,RLM,TIINTS
  C
  C -----------------
***************
*** 648,654 ****
  C
  C Read variables for the PRTST2 block:
  C
!           READ(NF,9140,END=200) IONCE4,ISTORC,NSTPSV
            READ(NF,9110,END=200) DSTOT,DETOT,RLM,TIINTS
        END IF
  C
--- 648,654 ----
  C
  C Read variables for the PRTST2 block:
  C
!           READ(NF,9140,END=200) IONCE4,ISTORC
            READ(NF,9110,END=200) DSTOT,DETOT,RLM,TIINTS
        END IF
  C
***************
*** 836,842 ****
  C
  C Write variables for the PRTST2 block:
  C
!           WRITE(NF) IONCE4,ISTORC,NSTPSV
            WRITE(NF) DSTOT,DETOT,RLM,TIINTS
  C
  C -----------------
--- 836,842 ----
  C
  C Write variables for the PRTST2 block:
  C
!           WRITE(NF) IONCE4,ISTORC
            WRITE(NF) DSTOT,DETOT,RLM,TIINTS
  C
  C -----------------
***************
*** 868,874 ****
  C
  C Write variables for the PRTST2 block:
  C
!           WRITE(NF,9140) IONCE4,ISTORC,NSTPSV
            WRITE(NF,9110) DSTOT,DETOT,RLM,TIINTS
        END IF
        RETURN
--- 868,874 ----
  C
  C Write variables for the PRTST2 block:
  C
!           WRITE(NF,9140) IONCE4,ISTORC
            WRITE(NF,9110) DSTOT,DETOT,RLM,TIINTS
        END IF
        RETURN
------------------------------------------------------------------------------


Temporary workarounds: 

     A simple workaround is available. Simply modify the overflowed
     field in the restart file (typically a six character-long field
     filled with "*"'s), replacing it with any arbitrary integer.
     E.g. "******" -> "000000". The value read from this field is
     not subsequently used, so it makes no difference what value
     is in the field.

Routines affected:

     GIBBS   Routine GETDYS in file ...amber4/src/gibbs/slwadj.f
     GIBBS   Routine WRTDYS in file ...amber4/src/gibbs/slwadj.f

--