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compute_inertia.cpp
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Sat, Aug 17, 00:24
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Mon, Aug 19, 00:24 (1 d, 23 h)
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rLAMMPS lammps
compute_inertia.cpp
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/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
http://lammps.sandia.gov, Sandia National Laboratories
Steve Plimpton, sjplimp@sandia.gov
Copyright (2003) Sandia Corporation. Under the terms of Contract
DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
certain rights in this software. This software is distributed under
the GNU General Public License.
See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */
#include "compute_inertia.h"
#include "update.h"
#include "group.h"
#include "error.h"
#include "math_extra.h"
using
namespace
LAMMPS_NS
;
/* ---------------------------------------------------------------------- */
ComputeInertia
::
ComputeInertia
(
LAMMPS
*
lmp
,
int
narg
,
char
**
arg
)
:
Compute
(
lmp
,
narg
,
arg
)
{
if
(
narg
!=
3
)
error
->
all
(
FLERR
,
"Illegal compute inertia command"
);
vector_flag
=
1
;
size_vector
=
3
;
extvector
=
0
;
vector
=
new
double
[
3
];
}
/* ---------------------------------------------------------------------- */
void
ComputeInertia
::
init
()
{
masstotal
=
group
->
mass
(
igroup
);
}
/* ---------------------------------------------------------------------- */
void
ComputeInertia
::
compute_vector
()
{
invoked_vector
=
update
->
ntimestep
;
double
xcm
[
3
];
group
->
xcm
(
igroup
,
masstotal
,
xcm
);
double
itensor
[
3
][
3
];
group
->
inertia
(
igroup
,
xcm
,
itensor
);
double
eigvect
[
3
][
3
];
int
ierror
;
ierror
=
MathExtra
::
jacobi
(
itensor
,
vector
,
eigvect
);
if
(
ierror
)
error
->
warning
(
FLERR
,
"Insufficient Jacobi rotations for principal moments of inertia"
);
// sort principal moments by size
double
tmp
;
if
(
vector
[
0
]
<
vector
[
1
])
{
tmp
=
vector
[
1
];
vector
[
1
]
=
vector
[
0
];
vector
[
0
]
=
tmp
;
}
if
(
vector
[
0
]
<
vector
[
2
])
{
tmp
=
vector
[
2
];
vector
[
2
]
=
vector
[
0
];
vector
[
0
]
=
tmp
;
}
if
(
vector
[
1
]
<
vector
[
2
])
{
tmp
=
vector
[
2
];
vector
[
2
]
=
vector
[
1
];
vector
[
1
]
=
tmp
;
}
return
;
}
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