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g2s - converts gadget to nemo snapshot file(s) using falcON


gagdet2nemo [parameter=value]


requires NEMO version 3.0.13 or higher, see


g2s tries to read gadget snapshots (gadget data format 1) and write them into a single nemo snapshot file. If the input has been different endianess than the local machine, the data are converted on the fly.


Gives the base file name for gadget snapshot data files. Default: required.
File name for writing data in nemo snapshot format. Default: required.
Number of snapshots to be converted. If nshot>1, we assume that there are snapshots fbaseXXX with XXX running from first to nshot-first+1. Otherwisw (if nshot==1), we assume the snapshot fbase to exists. Note that each snapshot can be distributed over several files, e.g. the 4th snapshot may be in 8 files "fbase004.0" to "fbase004.7". Default: 1.
Specifies which data are copied to the nemo snapshot file (and hence are assumed present in the gadget data files).

We assume that the gadget file contains the following data in this order: positions, velocities, keys (ids), masses (if not specified via the header), internal gas energies, gas densities, gas smoothing lengths, potentials, and accelerations. We stop reading the gadget data file once all data to be copied have been read (or the end of the file has been reached). Note that the first five are guaranteed to be always present. Default: mxvU.

If nshot>1, we assume the first snapshot to be converted to have index val. So, if e.g. first=4 and nshot=5, we seek to read snapshots "fbase004" to "fbase008". Default: 0.
Size (in bytes) of the FORTRAN record header used when the gadget data files have been written. This is usually 4, but on some 64bit machines it may be 8. Using a wrong value is likely to result in a fatal error with a completely misguiding error message. Default: 4.


Gadget is a massively parallel code and a single gadget snapshot distributed over several files may contain more data than can be hold in memory on just one node. Such snapshots cannot presently converted; the code is likely to crash when trying to grab too much memory.

see also



falcON/doc/user_guide.pdf               User Guide for falcON.


Walter Dehnen

update history of this man page

16-Feb-2007    first version of manual  WD

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