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Name

reb_integrate - example REBOUND integrator

Synopsis

reb_integrate [parameter=value]

Description

reb_integrate integrates an N-body snapshot from a REBOUND SimulationArchive (RSA), and writes an RSA. Programs such as s2reb(1NEMO) and reb2s(1NEMO) need to be used to convert from an to an RSA.

The number of integrators and particle types is limited, since this program is still more geared towards NEMO type simulations. This is work in progress.

While the integration is ongoing, results can be viewed in a browser by using a valid port number in server=, typically 1234 is used. The default will not use this progress viewer.

Parameters

The following parameters are recognized in order; they may be given in any order if the keyword is also given. Use --help to confirm this man page is up to date.
in=
input SimulationArchive. Currently the last snapshot in the file will be taken as the initial conditions for the integration. No default.
out=
output SimulationArchive. Note in REBOUND convention the integration results will be appended to an existing RSA. No default.
tstop=
Set, or let go forever [10]
dtout=
Optional interval to save simulation [1]
dt=
Integration Step [0.01]
eps=
Gravitational Softening Length [0.01]
integrator=
rebound integrator [leapfrog]
gravity=
none, basic, compensated or tree [basic]
tolerance=
tree opening angle - in radians? [0.25]
box=
Optional Simulation Box size - in terms or
G=
Gravitational Constant [1]
server=port

Use web based server on this port where the viewer can be seen on https://localhost:port

Example

Here is a comparison with NEMO’s directcode(1NEMO) , which uses a leapfrog integrator.

rm -f p100.?
mkplummer p100.a 100 seed=123
directcode p100.a p100.b freq=10 tstop=1 freqout=10 eps=0.05
s2reb p100.a p100.c
reb_integrate p100.c p100.d tstop=1 dt=0.1 dtout=0.1 eps=0.05
reb2s p100.d p100.e

snapcopy p100.b p100.f times=0,0.1,0.2,0.4,0.5,0.6,0.7,0.8,0.9,1.0
snapcopy p100.e p100.g times=0,0.1,0.2,0.4,0.5,0.6,0.7,0.8,0.9,1.0
snapcmp p100.f p100.g

with result from snapcmp(1NEMO) : 

0.1   1.07223e-07 6.2327e-05 0.000246797 0.000646361 0.00263568  0.000518528 0.000655015
0.2   2.14585e-07 0.000118829 0.000488151 0.00113191 0.00456865  0.000895096 0.00107481
0.4   4.29719e-07 0.000223833 0.000732012 0.00238062 0.00814445  0.00175906 0.00222084
0.5   5.37558e-07 0.000264628 0.000937241 0.00348549 0.0161293  0.00273714 0.00377185
0.6   6.45826e-07 0.000335195 0.00118023 0.00479002 0.0265185  0.00403516 0.00609259
0.7   7.55184e-07 0.000543983 0.00137947 0.00711976 0.0376623  0.00553559 0.00864033
0.8   8.66855e-07 0.000569031 0.00166312 0.0106839 0.0480827  0.00731209 0.0113419
0.9   9.82587e-07 0.000680878 0.00198077 0.0118269 0.0617785  0.00923201 0.0145423
1     1.1049e-06  0.000718976 0.00256446 0.0159907 0.0707068  0.0112444 0.0170355

so this does not appear to work quite yet. It also suffers from a roundoff error in time, plus the time=0.3 is never written, for which the peculiar snapcopy(1NEMO) was needed.

Caveats

Even though dt and dtout may look commensurate, this may result in snapshot dump times which are not properly "even"

Units used are virial units, except the Gravitational Constant can be changed (but not as function of time yet).

See Also

s2reb(1NEMO) , reb2s(1NEMO) , reb_viewer(1NEMO) , snapshot(5NEMO) , rebound(8NEMO) 
https://rebound.readthedocs.io

Files


NEMO/usr/hannorein/rebound - library source code
NEMO/usr/hannorein/nemo/reb_integrate.c - source code
NEMOLIB/librebound.so - linkable library

Author

Peter Teuben

History


17-jan-2024    Created        PJT

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