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Name

quadcode - global quadrupole-order N-body code integrator

Synopsis

quadcode in=snapshot [parameter=value] ...

Description

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)

Parameters

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.

Limitations

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.

See Also

quadforce(1NEMO) , quadinter(1NEMO) , CSG(1NEMO) , octcode(1NEMO)

Bugs

When a restart is specified, values must be given for ALL legal parameters which do not take default values.

Author

Joshua E. Barnes.

Files


src/nbody/evolve/multicode/    exported source code
usr/josh/nbody/multicode/    Josh’ original source code

History


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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