Modification of non-creatable array value attempted, subscript -49999

From: Pete Kekenes-Huskey (
Date: Tue Sep 06 2011 - 17:22:26 CDT

Dear all,
Has anyone encountered the error "Modification of non-creatable array
values attempted" while running

I have ran a series of TI calculations for the alchemical
transformation for a single point mutation of a protein. The
transformation was partitioned into twenty steps, each having 250000
steps of equilibration and another 250K steps for statistics, using
commands like this:

alch On
alchType ti
alchVdwLambdaEnd 0.5
alchFile $inputname.fep
alchCol O
alchOutfile $outputname.tiout
alchVdWShiftCoeff 6 # Enable soft-core vdW potential
alchElecLambdaStart 0.5 #
alchOutFreq 5
alchEquilSteps 250000

set Lambda 0.01
set Ival 0.05
alchLambda $Lambda
set Lambda2 [expr $Lambda +$Ival]
alchLambda2 $Lambda2
run 500000

I ran these files with the NAMD_2.7b4_Linux-x86_64 executable, the
jobs completed without error and the *tiout outputs seem to be
reasonable. When running (obtained from, I receive the
following error:

Ranger (E40A): ~/bin/ *tiout
Found 20 output files
Reading files: ....Modification of non-creatable array value
attempted, subscript -49999 at
/share/home/00623/tg457915/bin/ line 102, <FILE> line

Repeating the protocol for the files corresponding to lambda values
0..0.5 work fine, but files corresponding to lambda>0.55 fail with
this error. Any clues?

Thanks in advance for your help

Peter Kekenes-Huskey, Ph.D.
Postdoctoral Researcher
UCSD Dept of Pharmacology
4205 Urey Hall
9500 Gilman Avenue
La Jolla, CA 92093

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