read_restart or tandem runs?

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1

Hi dear users

What is the difference between using restart and then read_restart or using two runs tandem? I give different results when I use each other! I don’t specify units, boundary and atom_style in second run when I use tandem runs.

Thanks

Ly Xiang

2

Hi dear users

What is the difference between using restart and then read_restart or using
two runs tandem? I give different results when I use each other! I don’t
specify units, boundary and atom_style in second run when I use tandem runs.

what is a tandem run?
two run statements in the same input?

yes, there will be tiny differences at the continuation
point because writing a restart forces a neighborlist rebuild.

those tiny differences will grow exponentially
due to the "butterfly effect" since MD is a
"chaotic" system.

if those differences, however are large, then you
may be making a mistake or have discovered a
bug. in that case you have to provide the meads
to easily and quickly reproduce it.

axel.

3

Dear Axel
Thanks for your answer
yes there is large difference, I have a charged system and there is two different directions for flow
The only difference between my cods are that I don’t specify units, boundary and atom_style in second run when I use tandem runs as I said.
so wich one is reliable?
thanks

4

Dear Axel
Thanks for your answer
yes there is large difference, I have a charged system and there is two
different directions for flow
The only difference between my cods are that I don’t specify units, boundary
and atom_style in second run when I use tandem runs as I said.
so wich one is reliable?

i don't know. how could i?
i am no psychic, so i cannot
see your inputs and tell you
what you are doing wrong
and where.

axel.