Cactus Code Thorn EOS_Base
Author(s)    : Tom Goodale
Maintainer(s): Cactus team
Licence      : LGPL
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1. Purpose

This thorn provides a registration mechanism for various EOS.

These EOS can then be used by hydrodynamical routines.

Usage:

Creation of EOS:

A thorn providing an EOS should register that it does so by creating
an EOS handle with

int EOS_RegisterMethod(const char *name)

which returns a handle by which this EOS is referenced.

This handle can also be obtained at any time by calling

int EOS_Handle(const char *name)

Once the handle is created it can be used to register individual EOS
functions.  There are five of these

EOS_RegisterPressure         (int handle, CCTK_REAL (*func)(CCTK_REAL, CCTK_REAL))

   registers a function which returns pressure 
   as a function of rest mass density and specific internal energy

EOS_RegisterSpecificIntEnergy(int handle, CCTK_REAL (*func)(CCTK_REAL, CCTK_REAL))

   registers a function which returns specific internal energy  
   as a function of rest mass density and pressure

EOS_RegisterRestMassDens     (int handle, CCTK_REAL (*func)(CCTK_REAL, CCTK_REAL))

   registers a function which returns rest mass density  
   as a function of specific internal energy and pressure

EOS_RegisterDPressByDRho     (int handle, CCTK_REAL (*func)(CCTK_REAL, CCTK_REAL))

   registers a function which returns the derivative of pressure by
   rest mass density
   as a function of rest mass density and specific internal energy

EOS_RegisterDPressByDEps     (int handle, CCTK_REAL (*func)(CCTK_REAL, CCTK_REAL))

   registers a function which returns the derivative of pressure by
   specific internal energy
   as a function of rest mass density and specific internal energy

Usage from Fortran:

The Fortran usage is the same as the C usage.  If you register a
function from Fortran it is assumed to be a Fortran function.


Use of EOS by Hydrodynamics thorns:

There are five corresponding calling functions:

pressure = EOS_Pressure(handle, rho, eps)
eps      = EOS_SpecificIntEnergy(handle, rho, pressure)
rho      = EOS_RestMassDens(handle, eps, pressure)
dpdrho   = EOS_DPressByDRho(handle, rho, eps)
dpdeps   = EOS_DPressByDEps(handle, rho, eps)

each of these takes a handle as first argument, which should be
retrieved with

handle = EOS_Handle(name)

where 'name' is the name of the EOS.