Input data

Input format

In this section, we describe the different ways of loading your particle data into ASOHF. In particular, we describe the general reader format, and how to modify it and create your custom reader subroutine.

The general reader format

The general reader (subroutine READ_PARTICLES_GENERAL in the reader.f source file) assumes the data is contained in the file ./simulation/particlesXXXXX where XXXXX is the iteration number. The file is a binary file with the following format, record by record:

Redshift of the snapshot (single-precision real)
Number of DM particles (integer), $N_\mathrm{DM}$
X position of the DM particles ( $N_\mathrm{DM}$ single-precision reals)
Y position of the DM particles ( $N_\mathrm{DM}$ single-precision reals)
Z position of the DM particles ( $N_\mathrm{DM}$ single-precision reals)
Velocity component X of the DM particles ( $N_\mathrm{DM}$ single-precision reals)
Velocity component Y of the DM particles ( $N_\mathrm{DM}$ single-precision reals)
Velocity component Z of the DM particles ( $N_\mathrm{DM}$ single-precision reals)
Mass of the DM particles ( $N_\mathrm{DM}$ single-precision reals)
Unique ID of the DM particles ( $N_\mathrm{DM}$ integers)

If there are stars in the simulation (and it is so indicated in the parameters file; see the section on parameters), the following data is also read:

Number of stellar particles (integer), $N_\mathrm{stellar}$
X position of the stellar particles ( $N_\mathrm{stellar}$ single-precision reals)
Y position of the stellar particles ( $N_\mathrm{stellar}$ single-precision reals)
Z position of the stellar particles ( $N_\mathrm{stellar}$ single-precision reals)
Velocity component X of the stellar particles ( $N_\mathrm{stellar}$ single-precision reals)
Velocity component Y of the stellar particles ( $N_\mathrm{stellar}$ single-precision reals)
Velocity component Z of the stellar particles ( $N_\mathrm{stellar}$ single-precision reals)
Mass of the stellar particles ( $N_\mathrm{stellar}$ single-precision reals)
Unique ID of the stellar particles ( $N_\mathrm{stellar}$ integers)

The units of length, velocity and mass can be freely specified by the user (see the section on parameters).

If your input data uses double precision reals, please change the REAL*4 UBAS(0:PARTI_READ) line in READ_PARTICLES_GENERAL to REAL*8 UBAS(0:PARTI_READ). If you use over 2^31 particles, please compile with -fdefault-integer-8 (GNU) or -i8 (Intel) flags.

MASCLET users:

When using ASOHF coupled to MASCLET, take into account the MASCLET version and the flavour of the simulation to adapt the reader format (gridsXXXXX and cldmXXXXX files).

Creating your custom reader subroutine

You can alter the reader format by creating a custom subroutine in the reader.f source file, or modifying the READ_PARTICLES_GENERAL subroutine. If creating your own subroutine, set the correct call to it inside the READ_AND_ALLOC_PARTICLES subroutine in alloc.f.

In any case, leave the unit conversion loop unaltered,

DO I=1,N_DM+N_ST
    RXPA(I)=(RXPA(I)-CIO_XC)*FACT_LENGTH
    RYPA(I)=(RYPA(I)-CIO_YC)*FACT_LENGTH
    RZPA(I)=(RZPA(I)-CIO_ZC)*FACT_LENGTH

    U2DM(I)=U2DM(I)*FACT_SPEED
    U3DM(I)=U3DM(I)*FACT_SPEED
    U4DM(I)=U4DM(I)*FACT_SPEED

    MASAP(I)=MASAP(I)*FACT_MASS
END DO

and be sure to specify the correct input units in the asohf.dat file (see the section on parameters).

Contributing

If you have created a general reader routine for a widely-used, publicly-available simulation code and want it included in the public version of ASOHF, do not hesitate to create a pull request or to contact us.