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snapadd - adds N-body systems on top of each other


snapadd in=in1,in2,...out=snap_out [parameter=value ...]


This program adds up N-body systems by appending a number of snapshots to each other. Optionally the snapshots can be re-centered to their center of mass, though this is not the default. If the input files contain more than one snapshot, they are concurrently added (copying over the timestamp of the snapshot in the first file) until any of the files is exhausted.

If only two snapshots are added, snapstack(1NEMO) offers some more options, such as adding a relative shift in phase space. If more complicated shifts are necessary, snapshift(1NEMO) can be used before snapadd.

If you want to keep the snapshots separate, simple unix tools like cat(1) will work fine. For some of the older NEMO programs, embedded history could throw them off, and csf(1NEMO) should be used to create cleaner snapshots. See an example below.


The following parameters are recognized in any order if the keyword is also given:
in=in1, in2, ..
A number of input files can be supplied, separated by comma’s. They must all be in snapshot(5NEMO) format [no default].
output file, in snapshot(5NEMO) format [no default]
If true, translate to center of mass before output. [Default: f].
Forced output of: {acc, phi} []
Force time sync, based on first file in
Message header appended to any existing ones in the input files [default: none].


Snapshots only copy accross Mass (if they have it) and PhaseSpace.

See Also

snapstack(1NEMO) , snapmerge(1NEMO) , snapmerge_a(1NEMO) , snapshift(1NEMO) , snapcenter(1NEMO) , scf(1NEMO) , snapshot(5NEMO)


Peter Teuben


~/src/nbody/trans    snapadd.c


Although snapadd merges snapshots, if you want separate snapshots with their own timestamps, unix cat(1) will do just fine:
  % cat snap1 snap2 snap3 > snap.all
though this might throw off some older NEMO programs that cannot handle embeddded history tags. If so, filter them through csf(1NEMO) , e.g.:
  % csf snap1 snap.all
  % csf snap2 - item=SnapShot >> snap.all
  % csf snap3 - item=SnapShot >> snap.all

Update History

 6-May-87    V1.0: created              PJT
 8-Mar-87    V1.1: data history    PJT
xx-xxx-87    snapstack written by JEB
18-nov-90    V2.0: snapadd revived with multiple input    PJT
13-may-92    V2.2: added concurrent reading      PJT
15-jul-07    added examples (while at V2.5b)    PJT

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