Settings File¶

GPU v2.0 users

This page is oriented toward the CPU/v1.x documentation. For the GPU release, use the gevolution 2.0 settings reference.

This page summarizes all user-facing parameters. The first section documents every entry in the example settings file settings.ini (included in root). The second section lists all parameters that the code parses from user input via the reader defined in parser.hpp, including listing their default values that the code applies if they are absent in the settings file.

Settings.ini parameter overview¶

IC generation¶

IC generator — Selects the IC module. Options include basic, read, express, prevolution, song, relic, falconic depending on build. Example: basic.
template file — Gadget-2 particle template file used by IC generators. Example: sc1_crystal.dat.
tiling factor — Number of template replications per axis; total particles scale as \((\text{tiling factor})^3\). Example: 16.
Tk file — CLASS-format transfer functions file at initial redshift. Example: class_tk.dat.
baryon treatment — How baryons are represented: ignore, sample, blend, or hybrid. Example: blend.
seed — Random seed for the IC generator. Example: 42.
correct displacement — Enables template deconvolution into the displacement kernel (yes/no). Example: yes.
k-domain — Sampling domain in Fourier space: sphere or cube. Example: sphere.

Primordial power spectrum¶

k_pivot — Pivot scale in \(\mathrm{Mpc}^{-1}\) (not \(h/\mathrm{Mpc}\)). Example: 0.05.
A_s — Scalar amplitude. Example: 2.215e-9.
n_s — Scalar spectral index. Example: 0.9619.

Cosmology¶

h — Reduced Hubble constant. Example: 0.67556.
omega_b — Physical baryon density \(\Omega_b h^2\). Example: 0.022032.
omega_cdm — Physical CDM density \(\Omega_{\mathrm{cdm}} h^2\). Example: 0.12038.
T_cmb — CMB temperature in K. Example: 2.7255.
N_ur — Effective number of massless neutrinos. Example: 3.046.

Simulation¶

initial redshift — Starting redshift for evolution. Example: 100.0.
boxsize — Box size in \(\mathrm{Mpc}/h\). Example: 320.0.
Ngrid — Grid size per dimension. Example: 64.
Courant factor — Time stepping for gravity solver. Example: 48.0.
time step limit — Max step size in Hubble time units. Example: 0.04.
gravity theory — GR or Newton. Example: GR.
vector method — Vector solver: parabolic or elliptic. Example: parabolic.

Output¶

output path — Root output directory. Example: output/.
generic file base — Base name for generic outputs. Example: lcdm.
snapshot file base — Base name for particle snapshots. Example: lcdm_snap.
snapshot redshifts — Comma-separated snapshot redshifts. Example: 30, 10, 3, 0.
snapshot outputs — Snapshot fields (e.g. phi, B, Gadget2). Example: phi, B, Gadget2.
Pk file base — Base name for power spectra outputs. Example: lcdm_pk.
Pk redshifts — Comma-separated power-spectrum redshifts. Example: 50, 30, 10, 3, 1, 0.
Pk outputs — Pk fields (e.g. phi, B, chi, hij). Example: phi, B, chi, hij.
Pk bins — Number of Pk bins. Example: 1024.
lightcone file base — Base name for lightcone outputs. Example: lcdm_lightcone.
lightcone outputs — Lightcone fields (e.g. Gadget2, phi). Example: Gadget2, phi.
lightcone 0 vertex — Observer position in \(\mathrm{Mpc}/h\). Example: 0, 0, 0.
lightcone 0 direction — Viewing direction vector. Example: 1, 1, 1.
lightcone 0 distance — Comoving distance(s) in \(\mathrm{Mpc}/h\). Example: 100.
lightcone 1 vertex — Second lightcone observer position. Example: 0, 0, 0.
lightcone 1 direction — Second lightcone view direction. Example: 1, 1, 1.
lightcone 1 distance — Second lightcone distance range in \(\mathrm{Mpc}/h\). Example: 100, 450.
lightcone 1 opening half-angle — Half opening angle in degrees. Example: 30.

CLASS transfer-function options¶

output — CLASS output types (e.g. mPk, dTk, vTk).
gauge — CLASS gauge choice (e.g. synchronous).
P_k_ini type — Power spectrum type (e.g. analytic_Pk).
P_k_max_h/Mpc — Max \(k\) in \(h/\mathrm{Mpc}\) for CLASS output. Example: 192.
z_pk — Redshift for CLASS transfer tables. Example: 100.
root — Output file prefix. Example: class_.
extra metric transfer functions — Include extra metric transfer functions (yes/no).
background_verbose — CLASS background verbosity. Example: 1.
spectra_verbose — CLASS spectra verbosity. Example: 1.
output_verbose — CLASS output verbosity. Example: 1.

Parameters parsed from user input (parser.hpp)¶

Parameters below reflect the code path in parser.hpp and variables in metadata.hpp. Values marked “required” must be provided or the run aborts. All of these are available for the user to set, but for a basic run it is usually only the above parameters that one needs to set.

Initial conditions¶

seed — RNG seed for ICs. Default: 0.
IC generator — IC module selector. Default: basic.
particle file — Particle file(s) when IC generator = read. Default: required for read-from-disk.
template file — Template file(s) for particle tiling. Default: required for non-read ICs.
mPk file — Power spectrum file. Default: not set.
Tk file — Transfer function file. Default: not set.
correct displacement — Deconvolve template into displacement kernel. Default: no.
k-domain — Fourier sampling domain (cube or sphere). Default: cube.
tiling factor — Per-species tiling factors. Default: 1 for all species.
baryon treatment — ignore, sample, blend, hybrid. Default: blend (forced to ignore when mPk file is used or read-from-disk).
radiation treatment — background or CLASS (if built with CLASS). Default: background.
fluid treatment — background or CLASS (if built with CLASS). Default: background.
relaxation redshift — Redshift for relaxation step. Default: initial redshift.
restart redshift — Restart redshift for read-from-disk ICs. Default: not set.
cycle — Restart cycle index. Default: -1.
tau — Restart conformal time. Default: 0.
dtau — Restart conformal time step. Default: 0.
metric file — Metric file(s) for read-from-disk or RELIC ICs. Default: not set.
gevolution version — Version tag stored with restarts. Default: -1.
prevolution redshift — Start redshift for prevolution ICs. Default: required when using prevolution.
prevolution Courant factor — Time stepping during prevolution. Default: uses Courant factor when unset.
density file — Density input for RELIC ICs. Default: required for RELIC.
velocity file — Velocity input for RELIC ICs. Default: required for RELIC.
A_s — Scalar amplitude. Default: 2.215e-9.
n_s — Scalar spectral index. Default: 0.9619.
k_pivot — Pivot scale in \(\mathrm{Mpc}^{-1}\). Default: 0.05.

Simulation controls¶

vector method — Vector solver type. Default: parabolic.
gravity theory — GR or Newton. Default: GR.
boxsize — Box size in \(\mathrm{Mpc}/h\). Default: required.
Ngrid — Grid size per dimension. Default: required.
downgrade factor — Coarsening factor for grid. Default: 1.
Courant factor — Global time step factor. Default: 1.
time step limit — Max step size in Hubble time units. Default: 1.
move limit — Max particle move per step (grid units). Default: Ngrid.
initial redshift — Simulation start redshift. Default: required.

Output naming and paths¶

generic file base — Base for generic output names. Default: empty.
snapshot file base — Base for snapshot outputs. Default: snapshot.
Pk file base — Base for power spectra outputs. Default: pk.
lightcone file base — Base for lightcone outputs. Default: lightcone.
output path — Output directory. Default: empty (current working directory).
hibernation path — Output directory for restarts. Default: output path.
hibernation file base — Base for restart files. Default: restart.

Output scheduling and fields¶

snapshot redshifts — Redshifts for snapshots. Default: none.
Pk redshifts — Redshifts for power spectra. Default: none.
hibernation redshifts — Redshifts for restarts. Default: none.
hibernation wallclock limit — Wallclock limit in seconds. Default: -1 (disabled).
snapshot outputs — Field list; accepts: phi, chi, pot/psiN, B, P, T00/rho, Tij, rho_N, hij/GW, Gadget2, multi-Gadget2, Particles, cross, delta, delta_N, v. Default: none.
Pk outputs — Same field list as snapshots. Default: none.
lightcone outputs — Same field list as snapshots. Default: none.
Pk bins — Number of \(P(k)\) bins. Default: 64.
tracer factor — Per-species tracer subsampling. Default: 1 for all species.

Lightcones¶

lightcone vertex — Single lightcone observer position. Default: none (no lightcone unless set).
lightcone opening half-angle — Half-angle in degrees. Default: full sky.
lightcone distance — One or two distances in \(\mathrm{Mpc}/h\). Default: 0.5 * boxsize (and second distance 0).
lightcone redshift — Max redshift cut. Default: 0.
lightcone direction — Direction (2 angles or 3-vector). Default: (0, 0, 1).
lightcone pixel factor — HEALPix pixel dilation. Default: 0.5.
lightcone shell factor — Shell thickness factor. Default: 1.
lightcone covering — Extra covering factor. Default: \(2 + \frac{4}{\text{Courant factor} \cdot \text{shell factor}}\).
lightcone Nside — HEALPix resolution as two values (min/max). Default: [2, \text{next power of two} \ge Ngrid].
lightcone vertex — Multiple lightcones; same semantics as lightcone vertex. Default: none.
lightcone outputs — Per-lightcone output fields. Default: lightcone outputs.
lightcone opening half-angle — Per-lightcone half-angle. Default: full sky.
lightcone distance — Per-lightcone distance(s). Default: 0.5 * boxsize (and second distance 0).
lightcone redshift — Per-lightcone redshift cap. Default: 0.
lightcone direction — Per-lightcone direction. Default: (0, 0, 1).
lightcone pixel factor — Per-lightcone pixel factor. Default: 0.5.
lightcone shell factor — Per-lightcone shell factor. Default: 1.
lightcone covering — Per-lightcone covering. Default: \(2 + \frac{4}{\text{Courant factor} \cdot \text{shell factor}}\).
lightcone Nside — Per-lightcone HEALPix resolution. Default: [2, \text{next power of two} \ge Ngrid].

Cosmology¶

h — Reduced Hubble constant. Default: 0.67556.
m_ncdm — Masses (eV) of massive neutrino species. Default: none (all zero).
N_ncdm — Number of massive species. Default: inferred from m_ncdm count.
T_ncdm — Temperature ratio for massive species. Default: 0.71611.
deg_ncdm — Degeneracy factors for massive species. Default: 1.
T_cmb — CMB temperature in K (converted to \(\Omega_g\)). Default: not set.
omega_g — Physical photon density \(\Omega_g h^2\). Default: not set.
Omega_g — Photon density fraction. Default: 0.
N_ur — Effective massless neutrino count (converted to \(\Omega_{ur}\)). Default: 3.046.
N_eff — Alias for N_ur. Default: 3.046.
omega_ur — Physical massless neutrino density \(\Omega_{ur} h^2\). Default: not set.
Omega_ur — Massless neutrino density fraction. Default: computed from N_ur and \(\Omega_g\).
omega_fld — Physical dark-energy fluid density. Default: 0.
Omega_fld — Dark-energy fluid density fraction. Default: 0.
w0_fld — Dark-energy EOS \(w_0\). Default: -1.
wa_fld — Dark-energy EOS \(w_a\). Default: 0.
cs2_fld — Dark-energy sound speed. Default: 1.
Omega_smg — Modified-gravity density fraction. Default: 0.
omega_b — Physical baryon density \(\Omega_b h^2\). Default: 0.
Omega_b — Baryon density fraction. Default: 0.
omega_cdm — Physical CDM density \(\Omega_{\mathrm{cdm}} h^2\). Default: 1.
Omega_cdm — CDM density fraction. Default: 1.

Switching thresholds¶

switch delta_rad — Redshift for switching radiation density treatment. Default: 0.
switch delta_ncdm — Redshift(s) for switching massive species density treatment. Default: initial redshift for active species, else 0.
switch linear chi — Redshift for linearized \(\chi\). Default: 0 in GR, 0.011 in Newton (and at least max switch delta_ncdm).
switch B ncdm — Redshift(s) for switching vector modes of ncdm. Default: switch delta_ncdm.