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Name

firstn - von Hoerners first N-body code

Synopsis

firstn < firstn.in

Description

Arguably the first N-body code was written by von Hoerner (1960). This version, firstn, currently only integrates an example internally-generated Plummer sphere, and was written by S. Aarseth.

Input

The firstn.in input file contains 3 lines (See also nbody0(1NEMO) ).
N ETA EPS DELTAT TCRIT
ALPHAS BODY1 BODYN KZ5
Q, ISCALE
N - number of particles.
ETA - integration accuracy
EPS - gravitational softening (note vH used no softening)
DELTAT - time interval of data output.
TCRIT - final integration time
ALPHAS - slope of the IMF
BODY1 - lower cutoff in IMF
BODYN - upper cutoff in IMF
KZ5 - control parameter what kind of input data are generated.
Q - Initial virial ratio (1 meant 2T/W=1)
ISCALE -

Performance

CPU should scale as N^2. Here are some numbers
N    cpu"    cpu"
    ?    p4/1600/gcc    ifort
16    2.9    2.2    0.79
32    62.0    33.2    19.0
64    93.4    27.8    84.2
128    642.6    108.4    75.1
256    n/a    834.3    746.5

Caveats

This historic code is meant to be educational.

Author

S. von Hoerner (original), Sverre Aarseth (21st century adaptation)
Z.f.Astrophys. 50, 184, 1960 (1960ZA.....50..184V)
Z.f.Astrophys. 57, 47, 1963 
Files
~/usr/aarseth/firstn    original

See Also

nbody0(1NEMO)

History


dec-2000    version from Aarseth                       PJT
9-mar-04    man page written                 PJT


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