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mkgrid - create a cube of equal massive stars equally spaced in space
mkgrid out=snapshot [parameter=value]
mkgrid generates
a distribution of particles in a cube on a regular lattice.
The following parameters are recognized in order; they may be given in
any order if the keyword is also given. Use --help to confirm this man page
is up to date.
- out=
- Output file name, in snapshot(5NEMO)
format.
No default.
- ngrid=
- Number of particles per axis
[Default: 2].
- size=
- Size of cube.
[Default: 1].
- zerocm=t|f
- Center c.o.m. ?
[Default: t].
- headline=
- Text headline for output
Default: none.
- nmodel=integer
- Number of models to generate. All models will
be different here. Although mostly meant for benchmarks, generating more
then 1 model can be useful to process very large snapshots (that normally
won’t fit in memory) in a serialized fashion. See also snapsplit. Most NEMO
programs will only read the first snapshot. See also mkgrid nmodel= for
a faster way to benchmark.
[Default: 1]
The curious nmodel= parameter was added for benchmarking
the creation of large files. Very large Nbody snapshots would likely not
fit in memory, so this routine writes more (otherwise identical) snapshots.
There is a similar keyword in mkplummer(1NEMO)
but the CPU overhead is
killing the I/O bottleneck one likes to see with this keyword.
Here are
examples of making 1000 snapshot of 1e6 particles each, totalling 5GB with
both mkgrid and mkplummer, showing the impact of the CPU.
/usr/bin/time
mkgrid c1M 100 nmodel=100 1.61user 3.85system 0:29.52elapsed 18%CPU
/usr/bin/time
mkgrid . 100 nmodel=100 1.17user 1.21system 0:02.39elapsed 99%CPU
/usr/bin/time
mkplummer p1M 1000000 nmodel=100 25.31user 6.36system 0:56.65elapsed 55%CPU
/usr/bin/time mkplummer . 1000000 nmodel=100 24.29user 4.47system 0:28.78elapsed
99%CPU
mkcube(1NEMO)
, mkplummer(1NEMO)
, snapshot(5NEMO)
J.J.
Fleck
20-dec-05 created JJF
6-may-2025 added nmodel= PJT
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