Changes in the SimLine radiative transfer code

1.0 -> 1.1:

- restructuring of the field handling in the radiative transfer part,
  elimination of the emissivities -> 20% speed-up of the code
- Enabling compile-time and command line options giving the default
  values for the output file structure and setting overwrite mode
- Removal of a bug in the Sobolev part which could slow down the
  convergence in certain cases


1.1 -> 1.2:

- introduction of a first approximation for the treatment of turbulence
  and clumping in space or velocity space (effective optical depths)
  (Martin, Sanders & Hills 1984, MNRAS 208, 35)
- Addition of the turbulence correlation length as additional parameter
  in the set of physical input parameters
- Possibility to eliminate most of the annoying questions during the
  program execution by command line options or compiler directives


1.2 -> 1.21:

- removal of a severe bug in the central transfer code, addition of
  a second order term important for large velocity gradient regimes


1.21 -> 1.3:

- introduction of the treatment of a central HII region in the cloud
  core, addition of new physical parameters for the electron density 
  and temperature within the HII region
- new molecule added (SiO in the ground vibrational state)
- new collision rates for CS taken from Turner et al. 1992, ApJ 399,114,
  now all molecules except HCO+ can be treated at kinetic temperatures
  up to 300K
- improvement of the ray spacing in the final computation of the
  line profiles in case of large velocity gradients
- removal of a bug in the spatial intensity integration appearing at 
  density edges
- further exception handling added for very high intensities (e.g. 
  local masers)


1.3 -> 1.31

- removal of a bug in the transfer on the central ray which wasted
  computing time
- accuracy improvement for the routine computing the central optical 
  depth given as control output


1.31 -> 1.4:

- improvement of the accelerated lambda iteration, convergence speed
  up for large optical depths, "overshooting" prevented
- better extrapolation of the CO-ortho-H2 collision rates beyond 100K
  providing a smooth transition to the values for CO-para-H2
- addition of a two new observational parameters for a better map control
  (central offset and number of map points)
- increase of the size of all fields in frequency points


1.4 -> 1.5:

- introduction of new collision rates for HCO+ from T. Monteiro (1993)
  with up to 11 levels, now all molecules can be treated up to 300K
- removal of the rarely used input parameters lower and upper cut,
  cuts have to be introduced be the user via additional shells now
- increase of the maximum shell number
- acceleration of the convergence in the Sobolev part
- removal of two bugs which could prevent convergence in certain
  special cases at some machines
- modularized error treatment 


1.5 -> 1.51:

- removal of a format error writing a wrong comment line to some
  parameter files
- introduction of the background temperature as a free parameter, this
  makes old physical parameter files and population files incompatible


1.51 -> 2.0:

- name changed from LTR to SimLine since the original abbreviation 
  became meaningless
- removal of the molecular data from the code, they are now read
  from external files to obtain higher flexibility
- extension to arbitrary nonlinear molecules, this required changes in
  the input file format for observational parameters
- introduction of a data table treatment for the functional behaviour of
  the physical cloud input parameters, changes in that input file format
- introduction of FITS files as the default line output file format
- input of precomputed level populations as initial guess introduced
- definition of all field sizes in a single include file
- iterative improvement for large matrices introduced, acceleration
  of convergence for molecules with many transitions
- introduction of a smart maser treatment for weakly saturated masers


2.0 -> 2.01

- fixed bug that produced a numeric overflow at very high effective
  opacities in the macroturbulent description
- updated molecule files from JPL data base
- clean exception handling for zero collision rates introduced


2.01 -> 2.02

- improved accuracy of the small-tau approximation so that its range
  is extended now - small speedup
- fixed bug in the interpolation of the source function that could
  result in strong localized errors in case of considerable masering
- substituted linear extrapolation of collision rates at small 
  temperatures by square root extrapolation
- added more molecule files


2.02 -> 2.05

- Added option '-autonames' for an automatic generation of the names
  of the output files based on the input model name
- optical depth output added as a comment in the line files
- Transition from 0 to 0 generates a loop over all excited lines
- fixed small flaw in the call for the lambda iteration for level
  populations


2.05 -> 2.06

- Fixed wrong velocity order in FITS files
- Fixed a bug in the error handling when rewriting FITS files appearing
  with some compilers
- Reduced the range for the linear interpolation of the exponetials
- Added several molecules


2.06 -> 2.07

- Added new atoms/molecules: OI, CII, H2CO, CH3OH
- Updated constants for CI
- Fixed bug in the string handling of level names including spaces
- Introduced exception handling for levels with the same energy
- Restricted grid adjustment to significantly excited levels
- Increased accuracy in maser handling that could prevent convergence


2.07 -> 2.08

- Removed an inconsistent accuracy handling in sobolev introduced in 2.07
- added options -populateonly and -stoponerror
- Fixed a bug in the initial grid adjustment that could lead to a
  numerical singularity in case of strong negative systematic velocity
  gradients
- Added exception handling for floating point overflows in irrelevant
  collision rates


2.08 -> 2.09

- Improved handling of grid of rays in radiative transfer for observed lines
- Small adjustment of radial grid treatment
- reduced default value of epsz from 0.25 to 0.2
- Added error detection for temperatures below comsic background in input 


2.09 -> 2.10

- added exception handling for zero-width input shells
- added reader for LAMDA files
- added Windows libraries
- upgrade of Absoft compiler support to version 10.0


2.10 -> 2.11

- adaption of Makefile to new cfitsio library
- switch from g77 to gfortran for Linux
- indendation changed to be gfortran compatible


2.11 -> 2.12

- added exit codes to all stop commands for automatic fitting in MAGIX
- truncation of Gaunt factor approximation for high frequencies to prevent
  negative optical depths
- switch to composition of spline and trapezium integration for beam 
  integration as splines created overshooting in an extreme case