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This package provides some basic IO functionality to work with the Smoothed-Particle Hydrodynamics code Gadget by Volker Springel.

You can use it to read/write snapshot and subfind output and we also provide some functionality to read the log files.

It is taylored for working with the development version of P-Gadget3, specifically OpenGadget3 developed by Klaus Dolag and contributers. Development is focused on IO for Binary Format 2. A lot of the routines are based on IDL scripts by Klaus Dolag (not public).

If you use GadgetIO.jl in your publications please cite Böss & Valenzuela.

Please see the Documentation for details.

GadgetIO.jl is specialized to read Gadget snapshots of Format 2. The structure of a Format 2 snapshot is as follows:

8              # size of the blockname block (Int32)
BLOCKNAME      # Blockname (4*Char)
8+SIZE_BLOCK   # number of bytes to skip if block should not be read
8              # end of blockname block

SIZE_BLOCK     # size of the current block in bytes
{...}          # content of the block ordered by particle type
SIZE_BLOCK     # end of the current block

which repeats for every block.

Gadget defines 6 particle types:

• 0: Gas particles
• 1: DM particles
• 2: Disk/boundary particles
• 3: Bulge/boundary particles
• 4: Star particles
• 5: Black Hole particles

So if you want to read for example the poistions of gas particles you can do this by using:

julia``` filename = "path/to/your/snapshot"

gas_pos = read_block(filename, "POS", parttype=0)

Similar for DM particles:
julia```
filename = "path/to/your/snapshot"

dm_pos = read_block(filename, "POS", parttype=1)

We recommend running Gadget with the compiler flag WRITE_INFO_BLOCK to make IO easier, however you can also read most blocks out of the box due to fall-back InfoLines. If you work on a development version of Gadget that contains output blocks that don't have fall-back InfoLines you can also supply your own to the read_block function.

You can also read subvolumes of simulations, either along the Peano-Hilbert curve or in a brute force way. Or you can read particles by custom filtering and store the memory-mapping to disk. See the Documentation for details.