Domain error ParseFEP

From: Christian Jorgensen (christian.jorgensen_at_merton.ox.ac.uk)
Date: Fri Mar 25 2011 - 09:14:02 CDT

Hi all,
I am performing a bidirectional error analysis where
I run the forward and backward in a symmetric fashion
(same starting mutated file A/B)

runFEP 0.0 1.0 0.10 $nSteps ; # 10 windows outward (formally A------>B)
runFEP 1.0 0.0 -0.10 $nSteps ; # 10 windows outward (formally B----->A)

However, I keep getting the same error that prevents
me from carrying out the error analysis:

domain error: argument not in valid range
domain error: argument not in valid range
    while executing
"expr sqrt($instant_error_gauss) "
    (procedure "::ParseFEP::FEP_formula" line 361)
    invoked from within
"::ParseFEP::FEP_formula $file $file_entropy $file_lambda $window $mean_xi $fororback"
    (procedure "::ParseFEP::normal_parse_log" line 60)
    invoked from within
"::ParseFEP::normal_parse_log $::ParseFEP::fepofile forward "
    (procedure "::ParseFEP::namdparse" line 172)
    invoked from within
"::ParseFEP::namdparse"
    (in namespace inscope "::ParseFEP" script line 21)
    invoked from within
"::namespace inscope ::ParseFEP {
        ##if {$::ParseFEP::fepbofile != ""} {set ::ParseFEP::sosindex 1 }

        if { [string length $fepofile] < 1 } {
        tk_dial..."
    invoked from within
".parseFEP.runbutton invoke"
    ("uplevel" body line 1)
    invoked from within
"uplevel #0 [list $w invoke]"
    (procedure "tk::ButtonUp" line 22)
    invoked from within
"tk::ButtonUp .parseFEP.runbutton"
    (command bound to event)

As you can see from the ParseFEP log the process stops after window 7

#=================================================
# Free energy perturbation
# --------------------------------
#forward/backward λ ∆∆A ∆A δε
#
#-------------------------------------------------
forward: 0.0000 0.0000 0.0000 0.0000 WINDOW 1
forward: 0.1000 -0.5869 -0.5869 0.0575 WINDOW 2
forward: 0.2000 -0.6208 -1.2077 0.0920 WINDOW 3
forward: 0.3000 -0.5314 -1.7392 0.1049 WINDOW 4
forward: 0.4000 -0.5601 -2.2993 0.1250 WINDOW 5
forward: 0.5000 -0.3727 -2.6720 0.1333 WINDOW 6
forward: 0.6000 -2.6087 -5.2808 0.1683 WINDOW 7

My question: Has anyone encountered such an error before? Is my procedure correct or not?

Another possibility I have thought of is to do A--------->B
                                              extract last frame from dcd: B------------A
however this is not a 'symmetric' procedure in that both processes are run
as runFEP 0.0 1.0 0.10 $nSteps ; # 10 windows outward

thanks
Christian

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