sph.input

Every run is controlled by a Fortran namelist in sph.input. A minimal file sets only what it needs, and anything omitted takes the default below. The file begins with &input and ends with &end:

&input
 tf=200,
 n=20000,
&end

Note

The variables, defaults and descriptions on this page are read directly from the namelist declaration and the default-initialisation block in parallel_bleeding_edge/src/init.f. There are 76 settings.

Time and output

Variable	Default	Applies to	Meaning
`tf`	`50000`	every run	desired final time to stop simulation
`dtout`	`100`	every run	how often an out*.sph files should be dumped
`nitpot`	`1`	nothing, see below	number of iterations between evaluation of the gravitational potential energy.
`tjumpahead`	`1d30`	every run	time after which a wide orbit may be skipped rather than integrated. Only acts when tf is negative
`tscanon`	`0`	every run	time that the scan of a binary starts. The separation is held at sep0 until then, which gives the stars time to settle into the shape the corotating frame asks for
`sepfinal`	`1.d30`	every run	final separation for the scan of a binary, reached at min(tf,treloff). The scan is exponential in separation, so it changes by a fixed fraction per unit time. Set it equal to sep0 for a corotating run that does not scan
`throwaway`	`.false.`	every run	when skipping ahead, discard unbound ejecta rather than keeping all mass as two components

The particles

Variable	Default	Applies to	Meaning
`n`	`100000`	every run	desired number of particles. if n<0 then \|n\|=number of particles per solar mass. used only if making a new star.
`nnopt`	`22+gflag`	every run	controls neighbor number. leave it at 22 to get almost 40 neighbors.
`equalmass`	`0`	`1es` `1mc` `erg` `meq`	particle mass is proportional to rho^(1-equalmass), so equalmass=1 has equal mass particles and equalmass=0 is for constant number density.
`starmass`	`1d0`	`1es` `1mc`	mass of the polytrope to build, in solar masses
`starradius`	`1d0`	`1es` `1mc`	radius of the polytrope to build, in solar radii
`hco`	`-1d30`	every run	softening/smoothing length for compact object or core particle (<0 for auto-set)
`mco`	`-1d30`	`erg`	mass of compact object or core particle
`hfloor`	`0d0`	every run	hp(i) = hptilde(i) + hfloor, where hp(i)=smoothing length and hptilde(i) is used in eq.(A1) of GLPZ 2010.

Equation of state and physics

Variable	Default	Applies to	Meaning
`neos`	`1`	every run	0 for polytropic equation of state (eos), 1 for ideal gas + radiation pressure, 2 for tabulated eos
`gam`	`5.d0/3.d0`	every run	leave this set at a reasonable value even if using neos=1 or 2 (because the value of gam is used in estimating the local sound speed in balav3.f)
`nav`	`3`	every run	artificial viscosity (av) flag. leave it at 3 to get a hybrid balsara-monaghan av.
`alpha`	`1`	every run	av coefficient for term linear in mu
`beta`	`2`	every run	av coefficient for mu^2 term
`ngr`	`3`	every run	gravity flag. leave it at 3. if your want no gravity, ngr=0 might still work.
`nselfgravity`	`1`	every run	0 if just do gravity to point particles, 1 if self-gravitating
`nkernel`	`2`	every run	smoothing kernel: 0=cubic spline, 1=Wendland 3,3, 2=Wendland C4
`ncooling`	`0`	every run	0 if no cooling, otherwise radiative cooling
`teq`	`100d0`	every run	background temperature the cooling relaxes towards, in K. Only used when ncooling>0
`reat`	`-1.d0`	every run	radius within which a point mass swallows SPH particles. Negative disables eating

Relaxation

Variable	Default	Applies to	Meaning
`nrelax`	`1`	every run	relaxation flag. 0=dynamical calculation, 1=relaxation of single star, 2=relaxation of binary in corotating frame with centrifugal force, 3=calculation rotating frame with centrifugal and coriolis forces
`trelax`	`1.d30`	every run	drag timescale. 0 derives it from the model, a very large value disables the drag
`treloff`	`0`	every run	time the drag switches off and the run turns dynamical. It ends a scan as well, since a scan runs until min(tf,treloff). 0 asks for it to be derived as 10*trelax, which for a single star needs trelax=0 as well
`tresplintmuoff`	`0.`	every run	time to stop resplinting the mean molecular weight. leave this at 0.
`omega_spin`	`0.d0`	every run	angular rotation rate of star, used in nrelax=1 relaxations to give a rigidly rotating model

Orbit of the encounter

Variable	Default	Applies to	Meaning
`sep0`	`200`	every run	initial separation of two stars in a binary or collision calculation, and the separation a scan starts from and holds until tscanon
`rp`	`-1.d30`	every run	separation at closest approach. Set any two of rp, vinf2, e0 and semimajoraxis and the rest follow
`impactparameter`	`-1.d30`	`hbs` `hyp`	impact parameter at infinity, an alternative to rp, converted to it using angular momentum
`e0`	`-1.d30`	`bph` `hbs` `hyp`	orbital eccentricity: 1 is parabolic, above 1 hyperbolic, below 1 bound
`semimajoraxis`	`0.d0`	`bph` `hbs` `hyp`	orbital semimajor axis. 0 means unset, so that it is deduced from the others
`vinf2`	`1.d30`	`bph` `hbs` `hyp`	square of the relative speed at infinity. 1d30 means unset, so it is deduced from the others

Compact object and black hole

Variable	Default	Applies to	Meaning
`mbh`	`10d0`	`2cr` `hbs` `hyp`	mass of the point mass used as the second object when startfile2 is absent
`bbh_m1`	`-1d0`	`hyp`	first mass of a compact-object binary. Required, and only used, when bbh_m2 is positive
`bbh_m2`	`-1d0`	`hyp`	second mass of a compact-object binary. Negative means unset, giving a single point mass of mass mbh
`bbh_rp`	`-1.d30`	`hyp`	separation at closest approach for the compact-object binary
`bbh_semimajoraxis`	`0.d0`	`hyp`	semimajor axis of the compact-object binary. 0 means unset
`bbh_vinf2`	`1.d30`	`hyp`	square of the relative speed at infinity for the compact-object binary. 1d30 means unset
`bbh_e0`	`-1.d30`	`hyp`	eccentricity of the compact-object binary
`bbh_trueanomaly`	`0d0`	`hyp`	true anomaly of the compact-object binary, in degrees
`bbh_argperi`	`0d0`	`hyp`	argument of periapsis of the compact-object binary, in degrees
`bbh_inclination`	`0d0`	`hyp`	inclination of the compact-object binary, in degrees
`bbh_longitude`	`0d0`	`hyp`	longitude of the ascending node of the compact-object binary, in degrees

Timestep control

Variable	Default	Applies to	Meaning
`nintvar`	`2`	every run	1=integrate entropic variable a, 2=integrate internal energy u, 12=a then u
`cn1`	`.3d0`	every run	dt1=cn1*h/v_signal
`cn2`	`1.d30`	every run	dt2=cn2*(h/\|a-a_smoothed\|)^0.5
`cn3`	`0.1d0`	every run	dt3=cn3*u/\|du/dt\|
`cn4`	`1.d30`	every run	dt4=cn4*v_signal/\|a-a_smoothed\|
`cn5`	`0.02d0`	every run	dt5=cn5*r_ij/v_ij (minimized over all other particles j)
`cn6`	`0.02d0`	every run	dt6=cn6*(r_ij/a_ij)^.5 (minimized over all other particles j)
`cn7`	`4.d0`	every run	r_ij=(x_ij^2+y_ij^2+z_ij^2+cn7*h_i^2)^.5

Parallelism and GPUs

Variable	Default	Applies to	Meaning
`ngravprocs`	`0`	every run	the number of gravity processors (must be <= min(nprocs,ngravprocsmax))
`qthreads`	`0`	every run	number of gpu threads per particle. typically set to 1, 2, 4, or 8. set to a negative value to optimize the number of threads by timing. set to 0 to guess the best number of threads without timing.
`ppn`	`16`	every run	cpu cores per node, used to spread the gravity processes over nodes
`computeexclusivemode`	`0`	every run	set this to 1 if on machine like grapefree with gpus in compute exclusive mode; set this to 0 on supercomputers like lincoln
`gflag`	`1`	every run	set to 0 for g function from appendix of gaburov et al. (2010); set to 1 for a g function that works better when there are black holes

Units

Variable	Default	Applies to	Meaning
`runit`	`6.957d10`	every run	number of cm in the unit of length. use 6.957d10 if want MESA solar radius.
`munit`	`1.9884098706980504d33`	every run	number of g in unit of mass. use 1.9884098706980504E+033 if want MESA solar mass.

Input files

Variable	Default	Applies to	Meaning
`startfile1`	`'sph.start1u'`	`2cr` `bhe` `bph` `bps` `hbs` `hyp` `res` `tri`	first body of the encounter, in out*.sph format, usually the last snapshot of a relaxation
`startfile2`	`'sph.start2u'`	`2cr` `bhe` `bps` `hyp` `tri`	second body, same format as startfile1. If absent, a single point mass of mass mbh is used
`startfile3`	`'sph.start3u'`	`tri`	third body of a triple, same format as startfile1
`binaryfile`	`'input.bs'`	`2cr` `bps`	text file describing the binary, read by bps and 2cr
`triplefile`	`'input.3s'`	`bhe` `tri`	text file describing the third body, read by bhe and tri
`bpbhfile`	`'sph.bpbh'`	`bph`	text file giving the orientation angles and black hole mass, read by bph
`imagefile`	`'sph.image'`	`txt`	ASCII picture that txt turns into a particle layout
`advectedfile`	`'sph.passivelyAdvected'`	`hyp`	per-particle passively advected quantities, read by hyp when present
`eosfile`	`'sph.eos'`	every run	tabulated equation of state, read when neos selects a table
`opacityfile`	`'sph.opacity'`	every run	tabulated opacities, read when cooling needs them
`profilefile`	`'eg.last1.muse_s2mm'`	`erg`	stellar-evolution profile that erg builds its star from
`stellarevolutioncodetype`	`1`	`erg`	which code wrote profilefile, since the column layouts differ

Other settings

Variable	Default	Applies to	Meaning
`tswitchtou`	`-1.d0`	every run	nintvar=12: time to hand over from a to u. <0 means use treloff.