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firstn - von Hoerners first N-body code
firstn < firstn.in
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.
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 -
-
The
following parameter file should create the kind of spheres von Hoerner
was using in his 1960 paper:
16 12.0 0.0 1.0 10.0
1.0 1.0 1.0 0
0.5 0
It should be noted in the 1960 paper N=4,8,10,12,16 were used, in the 1963
followup paper N=25 was used. Computational time should scale N^4 per relaxation
time.
CPU should scale as N^2. Here are some numbers from "make
bench":
N cpu" cpu"
? p4/1600/gcc ifort i5-1135G7
16 2.9 2.2 0.79 0.23
32 62.0 33.2 19.0 1.67
64 93.4 27.8 84.2 16.11
128 642.6 108.4 75.1 8.25
256 n/a 834.3 746.5 44.8
This historic code is meant to be educational.
~/usr/aarseth/firstn original
nbody0(1NEMO)
, mkvh60(1NEMO)
Z.f.Astrophys. 50, 184, 1960
Z.f.Astrophys. 57, 47, 1963
@ads 1960ZA.....50..184V
S. von Hoerner (original),
Sverre Aarseth (21st century adaptation)
dec-2000 version from Aarseth PJT
9-mar-04 man page written PJT
19-apr-21 reference to mkvh60 PJT
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