This document describes how variable names are constructed in the source files of BHAC. This was done rigorously in VAC, and in BHAC we have kept most of the naming conventions, but introduced new structure to handle the AMR grid hierarchy. The patterns starting with ^ are expanded by the VACPP preprocessor. The meaning of some tokens is given below.
This page: [Equation] [Dimensions] [General] [Grid] [I/O] [Method] [Subroutine] [Examples]

Differential Equations and Physical Quantities

pw(igrid)%w  	:	w	- flow variables
pws(igrid)%w  	:	ws	- staggered flow variables
px(igrid)%x	:	x	- spatial variables

fC	- flux, defined at cell edges

t	- time
it	- integer time counter
r_	- R   direction for polar or cylindrical symmetry
phi_    - PHI direction for polar or cylindrical symmetry
z_      - Z   direction for polar or cylindrical symmetry

zero	- 0.D0
one	- 1.D0
two	- 2.D0
half	- 0.5D0
quarter - 0.25D0
dpi     - the value of pi (double precision)

smalldouble -a small number above machine precision
bigdouble   -a very large number

Dimensions, Directions, and Limits

dim	- dimension or direction
^D	- expands to 1,..,ndim
^ND	- expands to the value of ndim
dir	- direction (of vector variables)
^C	- expands to 1,..,ndir (Component)
^NC	- expands to the value of ndir
*min	- minimum of * (expected, or actual)
*max	- maximum of * (expected, or actual)
^LIM	- expands to min,max
^L	- expands to min1,min2,min3,max1,max2,max3
^S	- expands to min1:max1,min2:max2,min3:max3
*lo	- lowest  value of * (enforced by array boundaries)
*hi	- highest value of * (enforced by array boundaries)
^LLIM	- expands to lo,hi
^LL	- expands to lo1,lo2,lo3,hi1,hi2,hi3
^T	- expands to lo1:hi1,lo2:hi2,lo3:hi3

General Tokens

i*	- index for *
h*	- i*-1  Previous index
j*	- i*+1  Next index
n*	- number of *. Usually refers to an index i*=1..n*.
d*	- difference of *, derivative of *
grad*   - spatial derivative of *
l*	- limited value
*C	- add 1/2 to spatial index/indices
*CT	- add 1/2 to temporal index
*R	- on the right
*L	- on the left
*I	- input  (eg. ixI^L are the limits of useful part of input)
*O	- output (eg. ixO^L are the limits of useful part of output)
*2	- on the power two, squared
sqr*	- square root of
kr	- Kronecker delta 3*3 tensor
lvc	- Levi-Civita 3*3*3 tensor
^LEN*	- length of string for *
q*	- local variables to avoid name conflict with common ones
special*- user defined subroutines and parameters
*_	- indexname, integer parameters defined for legible code

Grid Related Tokens

G	- grid (boundaries included)
grid	- grid (boundaries included)
M	- mesh (without boundary layers)
mesh	- mesh (without boundary layers)
B	- boundary
dixB	- boundary width
volume	- volume of mesh
dvolume	- volume of cell
surface	- surface of cell edge
normal	- normalized normal vector of cell surface 

I/O Related Tokens

file	- input/output files
read    - reading from parameter or data files
save	- writing into output files
last	- last occasion (e.g. for saving into file)
*ini	- file containing initial conditions
*out	- file containing full results
head	- header string in files
name	- names (e.g. filename, variables, w)
wnames	- names of all w variables (e.g. 'rho m1 m2')
unit	- units for open, close, read and write statements
unitterm- standard output

Method Related Tokens

type*	- types (e.g. boundary, flow variables)
par	- parameters
eq	- equation
fix	- fixing certain problems (e.g. divbfix)
error	- error quantification
err	- same as error
courant	- Courant condition
step	- step in multistep methods
pred	- predictor (or half) step
full	- full step
advance - advancing from time t to t+dt
advect  - advecting in directions idimmin..idimmax
advect1 - a single step of a multistep time integration in advect
method	- spatial discretization method

Subroutine Name Tokens

get*	- subroutine names for getting values (e.g. getflux)
add*	- subroutine names for adding values  (e.g. addsource)


For example the variable name

ditsave = d + i + t + save
is the difference in the indices of the times between saves into the output files, i.e. the frequency of saving snap shots measured in time steps. Another example:
ixGhi^D = i + x + G + hi + ^D
is the highest possible indices for the coordinates for the grid for each dimensions.