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snapcmp - compare two N-body snapshots
snapcmp in1=snap_file
in2=snap_file [parameter=value] ...
snapcmp is a flexible tool
for comparing two N-body snapshots on a particle by particle basis. An arbitrary
‘‘observable’’ defined in terms of the basic components of a body(3NEMO)
may
be specified for the comparison. Particles are compared by differencing
their observables, or by computing the observable applied to a differenced
particle. These options cover most of the common methods of comparing N-body
snapshots. The default settings compute the magnitude of the configuration-space
displacements between each pair of particles.
The program simply outputs
eight numbers: time of the first snapshot, are the minimum, lower quartile,
median, upper quartile, maximum of the measured differences, and the mean
and dispersion of the distribution.
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.
- in1=snap_file1
- in2=snap_file2
- Input data is read from snap_file1 and snap_file2, which
must be in snapshot(5NEMO)
format.
Default: none.
- time1=time_range1
- time2=time_range2
- Data with time values
within time_range1 and time_range2 will be read from snap_file1 and snap_file2,
respectively.
[Default: all].
- obs=obs_expression
- obs_expression is the observable used
to compare the particles. See bodytrans(1NEMO)
for the form of obs_expression.
Default: r, which compares the positions of particles.
- diffpart=flag
- If
flag is true, particles are compared by subtracting the components of one
from the components of the other, and evaluating the observable obs on
this ‘‘differenced particle’’. Otherwise, obs is evaluated for each particle,
and the results are differenced.
Default: true.
- relative=flag
- If flag is true, the differenced observable
is divided by the value of obs computed from the particle in snap_file1.
Otherwise, the differenced observable is used.
Default: false.
- log=t|f
- Show (10-base) logarithms of the values instead of
their linear values
Default: false.
- time0=t|f
- Also print time=0?
Default: true
Two random Plummer spheres are compared in the
X coordinate:
$ mkplummer p1 1000 seed=123
$ mkplummer p2 1000 seed=456
$ snapcmp p1 p2 obs=x
# time Min Qlow Median Qhigh Max Mean Sigma
# obs=x (linear scaling)
0 -12.7064 -0.565549 -0.0109623 0.611036 11.8118 -1.15463e-16 1.61843
snapcmphist(1NEMO)
, snapdiff(1NEMO)
, bodytrans(3NEMO)
, snapshot(5NEMO)
src/nbody/reduc/snapcmp.c source code for snapcmp, snapcmphist and
snapcmpplot
Joshua E. Barnes.
23-may-88 V1.0 created? Josh
29-mar-94 V1.3 added time to output Peter
15-apr-04 V1.5 added headline= to the plotting versions and mean,sigma to
the output PJT
16-jul-09 V1.6 added log= PJT
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