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quadcode - global quadrupole-order N-body code integrator
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)
following parameters are recognized; they may be given in any order.
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:
- Snapshot with initial conditions. No default.
- Output file, will
be in standard snapshot(5NEMO)
format. No default.
file which will contain the quaddrupole-order field tables. Default: not
- If given, the system state will be saved in state-file
after each timestep. Default: not used.
- Force softening
parameter in radial direction. Default is 0.05.
softening parameter in angular directions. Default is 0.07.
- Inverse time-step, to be used with a leap-frog integrator. Default is 64.0
(64 steps per unit time).
- Mode of integration. 1 = Runge
Kutta, 2 = PC, 3 = PC1. [Default: 3].
- Time to stop integration
in N-body model units. Default is 2.0.
- Frequency of major N-body
data and quadrupole field table outputs. (out= and quad=) Default is 4.0
(4 frames per unit time).
- 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).
- 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
% 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.
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
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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