Initial conditions / writing your own setup routine

Steps are:

  1. check that a setup routine for your problem does not already exist.

  2. copy one of the existing setups (e.g. setup_unifdis.f90) to a new file (e.g. setup_myproblem.f90).

  3. edit this file.

  4. set this as the SETUPFILE= within your SETUP block in build/phantom/Makefile_setups.

  5. compile phantomsetup (“make setup” in the run directory).

Setting up additional particle arrays

The important arrays that require filling are explicitly passed to the setpart routine:

subroutine setpart(id,npart,npartoftype,xyzh,massoftype,vxyzu,polyk,gamma,hfact,time)

Other arrays can be setup by importing them via the usual code modules. For example, to set up sink particles, import the arrays with:

use part, only:xyzmh_ptmass, vxyz_ptmass

and set these to the appropriate values.

Setting default values for runtime options

Since phantomsetup is also responsible for (re)writing the initial runtime options file, it is also possible to provide default options for runtime parameters in the setup routine. Just import the relevant parameters from the relevant module:

use options, only:alpha,alphau

These variables can be edited as usual in the .in file at runtime, but is a good way of giving sensible defaults (note however, that setting runtime options in your setup routine will cause them to be overwritten in the .in file every time you run phantomsetup; to prevent this, you can declare the default values only if the .in file does not exist).

The .setup files

Several of the existing setup_*.f90 subroutines write .setup files whose values are only required only to initialise the problem. For these setup files, when phantomsetup is run for the first time with a given file model prefix, then it will interactively ask for the required values; on all subsequent runs, phantomsetup will read these values from the .setup file. If options are to be added to these setup files, then they must be added in the interactive question section, the write_setupfile subroutine, and the read_setupfile subroutine (all three sections will be present in the subroutine).

Utility routines

There are several routines in the libsetup library to assist with setting up the particle positions:




sets up a uniform particle distribution with particles set on various lattice options


sets up a uniform density sphere (interface to set_unifdis)


sets up a single accretion disc with given surface density and temperature profiles


sets up a binary consisting of two point mass particles with all 6 orbital elements


sets up a thin slab for 2D tests done in 3D

Try to use these wherever possible. This makes the setup routines much simpler and means less cut-and-pasting between otherwise similar setups. For example, it is perfectly valid to have a setup routine that sets up a single disc with different parameterisations of Rin, Rout, but you should achieve this by a simple setup_blah.f90 file that just calls set_disc.

Internal labels

Try to refer to particle types and array components by their parameterised labels in the part module. That is, use

npartoftype(igas) = 1000000

rather than

npartoftype(1) = 1000000

Similarly, you should NEVER set or use iphase directly, instead you should use the interface routines in the part module (isetphase, iactive, iamgas, iamdust, iamtype) to set/extract the relevant information