Thank you for your reply! At the moment I found a work around. I am using
the coordinates given by leap to manually replace a solvent atom with the
ion, then run again leap, repeat this until I neutralize the structure.
Another option for me is instead adding 10 Cl- ions to remove 10 K+ ions
so that overall I have a neutral structure. This does not significantly
change the molarity of the solution.
I do have an additional question and maybe this is the right time to ask.
I know that the "solvate" command in Leap uses a pre-equilibrated
water box approximately 18A in dimension. Where and what exactly I should
change to have instead the WATBOX216 my own preequilibrated box with ionic
solution this time.
The two options I think I have at the moment are:
1. To try and change the parameters of the WATBOX216 in
$AMBERHOME//dat/leap/lib/solvents.lib
2. To use the "zToolSolvateAndShell" routine from tools.c in
$AMBERHOME/src/leap/src/leap and build a separate code on it.
The first solution seems easier to try but I would like to know if I
should change anything else except the WATBOX216 parameters in
solvents.lib?
If I decide to use the second option, I would like to know the exact steps
the solvate command is taking:
1. It considers the Lx, Ly and Lz dimensions of the solvent, adds to it
the buffer and then divides these numbers by the size of the solvent
box to find how many solute boxes are needed in each direction. How does
it deal with non integer numbers? What is the approximation considered?
2. Does it then calculate the center of the solute and overlaps the first
solvent box with it? Or does the solvation procedure start from a corner?
Any help with this would be more than appreciated.
Thank you in advance,
Ioana
On Thu, 22 Jan 2004, Bill Ross wrote:
> > > > Placed Cl- in foo at (34.61, -13.78, 49.32).
> > > > Segmentation fault (core dumped)
> > > >
> > > > Does anyone have any idea what may be wrong in this case? Could it be that
> > > > there is a memory problem?
> > >
> > > There is. As a workaround you could try adding Cl-'s one-by-one
> > > explicitly.
> >
> > I am not sure how I could trace this down. I'm running tleap on one
> > processor, but it does not seem to be eating up memory (swap memory does
> > not change). I've also tried to run tleap in a pbs job asking for 1Gb of
> > memory and still I get a segmentation fault.
>
> That's because the code is buggy, such that an array index
> points into unallocated memory or some such. This is what
> I meant by a memory problem, sorry for the miscommunication.
>
> > I've also tried to add Ions one by one but it does not seem to matter.
>
> This raises the priority of the bug.
>
> > What seems strange is that the charge calculation over the grid is
> > completed and only after the ion is placed the segmentation fault happens.
>
> The grid is maintained as an "octree" which is the 3-dimensional
> version of a binary tree (saves memory). When the ion is placed,
> the tree is updated to remove the grid points overlapped by the
> ion and to update the charges. This is what causes the seg fault.
>
> > I also remember working some while ago with larger files than the present
> > one and never got a segmentation fault.
>
> Presumably it depends on the layout of the grid or the number of
> atoms.
>
> > I know this sound very imprecies but I'm looking for help to find a
> > starting point to try and trace this down.
>
> At one point I used the Purify program, which is excellent at
> showing where memory abuse is occurring in a running program.
> By this method and much effort I found two bugs, but they did
> not solve the problem I was seeing and I did not apply them to
> the code because I didn't want to cause other problems, given
> that there was a workaround. Unfortunately I lost that version
> of the code when the Kollman lab was dismantled and the machine
> it was on was recycled. It may still exist on another group's
> machine that I did the work on, I'll look into it. Meanwhile
> if you have access to Purify, that would be the way to go.
>
> Per David Konerding, valgrind may be worth a try too.. it s
> free, very new. Purify is commercial and very mature (with
> some top people supporting it I happen to know).
>
> Bill Ross
>
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Received on Fri Jan 23 2004 - 07:53:01 PST
