Hi Axel and Everyone,
Thanks for fast response!
this sounds a lot like you are misunderstanding this sentence.
"multiple runs" in this context means: multiple run commands in the
same file. it does *not* refer to restarts directly.
Indeed. My problem is that I need to break down a deformation
into multiple subsequent simulations due to max time my job
can run on the queue. Btw. I'm stretching ~5M bead large
Kremer-Grest polymer melts and networks until the FENE bonds
start breaking.
run 400
run 100 stop 400
run 100 start 100 stop 400
run 100 start 200 stop 400
run 100 start 300 stop 400
of course, you can break this down into separate inputs and do a
write_restart at the end and a read_restart at the beginning of each
segment.
4X "run 100 start 0 stop 400", but I agree, you wil get the same result.
Now instead try for the sake of the argument
run 100 start 0 stop 400
unfix def
fix def all deform ...
run 100 start 0 stop 400
unfix def
fix def all deform ...
and so on, where the deform arguments are the same.
And you will get a very different result, in fact if you specify a constant engineering strain
rate you will get a constant true strain rate, since each new fix def will use the instantaneous
box, not the initial undeformed box as reference. The problem is the same when I am
restarting my simulation multiple times to continue the deformation.
Which is why the simplest solution is to allow the user to specify the initial box
shape to fix deform, since this information needs to be propagated from one
simulation to the next in some form. Alternatively, the user has to keep track
of e.g. renormalizing strain rates in the correct way when restarting the simulation.
I don't get the idea of using change_box since the current box shape is the
result of the strain history of the simulation, I don't want to change that.