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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 -

Examples

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.

Performance

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

Caveats

This historic code is meant to be educational.

Files


~/usr/aarseth/firstn    original

See Also

nbody0(1NEMO) , mkvh60(1NEMO)


Z.f.Astrophys. 50, 184, 1960
Z.f.Astrophys. 57, 47, 1963 

Ads

@ads 1960ZA.....50..184V

Author

S. von Hoerner (original), Sverre Aarseth (21st century adaptation)

History


dec-2000    version from Aarseth                       PJT
9-mar-04    man page written                 PJT
19-apr-21    reference to mkvh60    PJT


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