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quadcode - global quadrupole-order N-body code integrator
quadcode
in=snapshot [parameter=value] ...
quadcode is an equal-timestep
implementation of an N-body code where the forces and potential are computed
from a potential expansion in spherical harmonics (S. White, Ap.J. 274, 53
(1983), who dubbed it multipole expansion). See also a followup in Bontekoe
& van Albada (MNRAS 224, 349 (1987)) and a rebuttal in Zaritsky & White (MNRAS
235, 289 (1988). See also Hernquist, L. & Barnes, J. Ap.J. 349, 562 (1990)
The
following parameters are recognized; they may be given in any order.
- in=in-file
- Snapshot with initial conditions. No default.
- out=out-file
- Output file, will
be in standard snapshot(5NEMO)
format. No default.
- quad=quad_table
- Output
file which will contain the quaddrupole-order field tables. Default: not
used.
- save=state-file
- If given, the system state will be saved in state-file
after each timestep. Default: not used.
- eps_r=rad_soft-length
- Force softening
parameter in radial direction. Default is 0.05.
- eps_t=theta_soft-length
- Force
softening parameter in angular directions. Default is 0.07.
- freq=integ-freq
- Inverse time-step, to be used with a leap-frog integrator. Default is 64.0
(64 steps per unit time).
- mode=integration-mode
- Mode of integration. 1 = Runge
Kutta, 2 = PC, 3 = PC1. [Default: 3].
- tstop=stop-time
- Time to stop integration
in N-body model units. Default is 2.0.
- freqout=out-freq
- Frequency of major N-body
data and quadrupole field table outputs. (out= and quad=) Default is 4.0
(4 frames per unit time).
- minor_freqout=out-freq
- Frequency of minor diagnostic
outputs. If this frequency is not a simple fraction of freq (see above),
the program can waiste significant amounts of time. Default is 32.0 (32 diagnostic
measurements per unit time).
- options=option-string
- Miscellaneous control
options, specified as a comma-separated list of keywords. Currently recognized
keywords are: reset_time: when reading initial data, set tnow to zero;
mass, phi, acc: output mass, potential, acceleration data with major data
outputs. The phase space coordinates are always output. The default is
blank, meaning only phase space coordinates are output. No additional information
is output.
The code has a hardcoded maximum number of particles,
through the macro MBODY. (currently 4096). If more are needed, it needs to
be recompiled, for example:
% make quadcode quadforce quadinter MBODY=16384
(Note that all quad* programs need to (should) be recompiled if the maximum
allowed number of bodies will be changed.
quadforce(1NEMO)
, quadinter(1NEMO)
,
CSG(1NEMO)
, octcode(1NEMO)
@ads 1983ApJ...274...53W
or should we link White’s 1978MNRAS.184..185W paper
When a restart is
specified, values must be given for ALL legal parameters which do not take
default values.
Joshua E. Barnes.
src/nbody/evolve/multicode/ exported source code
usr/josh/nbody/multicode/ Josh’ original source code
4-mar-89 V1.2 some formal NEMO version JEB
12-nov-91 V1.3 new NEMO V2. location in $NEMO/src tree PJT
6-may-92 document improved PJT
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