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Re: [lammps-users] serial_mpi


From: Cunzhi Zhang <zcz1005@...2045...>
Date: Fri, 4 May 2018 00:58:37 -0500

Hi,

my input is shown below:

variable x equal 4
variable y equal 4
variable z equal 4
variable rho equal 0.6
variable        t equal 1.35
variable rc equal 2.5

units lj
atom_style atomic

lattice fcc ${rho}
region box block 0 $x 0 $y 0 $z
create_box 1 box
create_atoms 1 box
mass 1 1.0

velocity all create $t 87287

pair_style lj/cut ${rc}
pair_coeff 1 1 1.0 1.0

neighbor 0.3 bin
neigh_modify delay 0 every 1

velocity all scale $t

fix        1 all nve


thermo        1
thermo_style    custom step temp #v_Jx v_Jy v_Jz 

dump    1 all custom 1 dump.lammpstrj id type x y z vx vy vz

run             10

Thanks.


On May 4, 2018, at 12:49 AM, Diaz,Adrian <adriandiaz@...1447...> wrote:

your input would be required to make a rigorous judgement here, numerical error is normal but that does look pretty hefty for just ten timesteps.

From: Cunzhi Zhang <zcz1005@...2045...>
Sent: Friday, May 4, 2018 1:21:05 AM
To: LAMMPS
Subject: [lammps-users] serial_mpi
 
Dear lammps community

        I launched two MD simulation with same input, but one case is serial (lmp_serial), and another case is in parappel (lmp_mpi).

        I found that the trajectory of the two is not exactly the same, 

# case one (mpi)
Step Temp         
0         1.35        
1    1.3504087        
 2    1.3516204         
3    1.3535921        
 4    1.3562505         
5     1.359487         
6    1.3631512         
7    1.3670437         
8    1.3709075         
9    1.3744185        
10    1.3771613 

# case two (serial)
Step Temp        
0         1.35         
1    1.3503972         
2    1.3515752         
3    1.3534922         
4    1.3560752         
5    1.3592151         
6    1.3627588         
7    1.3665005         
8    1.3701724         
9    1.3734388        
10    1.3758609 

    So, is this kind of difference expected or am I doing something very wrong?

Thanks

Cunzhi
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