User Defined Spectral Models
EXSAS is designed to allow a user to include his own
spectral models. Up to 20 additive (ua01,
, ua20) and
multiplicative (um01, ,
um20) user defined models can be added to
the spectral analysis package at run time. The code
of a user defined model can be written in any language
(i.e. FORTRAN, C, etc.) as long as the user takes care
of appropriate variable and function call handling and
referencing to the EXSAS FORTRAN 77 code. An example
of an additive user defined spectral model can be found
in
An example of a user defined multiplicative model is given in
In general, a user defined model has to have the same parameter list as given in the following FORTRAN examples:
Here, E is the energy variable and P the parameter list of
NP model parameters. The output parameters are the photon
flux F and an error flag, which can be set to 0, if no
important decision has to be made. The variables E, P and F
have to be declared as double precision, the remaining two
parameters NP and IERR as integer. The unit of the independent
variable E is keV and of the dependent variable F is keV
s cm 
.
Before adding one or more user defined spectral models to EXSAS
one has to define an environment variable $user_def (for
example in your login file) which defines the path to a directory
where the source code of your model is stored.
Assume you run EXSAS on a UNIX like operating system and you want
to include an additive spectral model, something like a modified
power-law or so. The model is your first and only user defined
spectral model you want to add to EXSAS.
Let's call the file with the FORTRAN code of your model
ua01.for. Make a subdirectory, for example named
my_models using mkdir /home/..../my_models and define
the path to it in your .login file by adding the line
setenv user_def /home/....../my_models to your login script.
Then copy the shell script $XEXSAS/spectral/modespe/modespe.sh
to the $user_def directory and make sure that it is executable
(chmod u+x modespe.sh). This script file comes with EXSAS and
was designed to help you with the inclusion of your model (compilation,
linking, copying of library files to $user_def etc).
Assuming now that you are in $user_def and have copied modespe.sh to this directory, executing
from the UNIX command line will then first copy the EXSAS spectral
model library modespe.a and the FORTRAN source code
modespe_p.fom of the EXSAS executable modespe.exe
to your directory $user_def. Subsequently ua01.for
will be compiled to ua01.o and added to the library
modespe.a. Finally the EXSAS executable modespe.exe
is created by compiling modespe_p.fom and linking it with
modespe.a. If there is no error in your model file
ua01.for and the script file modespe.sh
finished successful the file modespe.exe is created in
the directory $user_def.
If you want to include more as one user defined model just give all model names separated by a "," as parameter to modespe.sh, for example like:
Note that you have to add all your user defined models in one step since the default EXSAS spectral model library modespe.a is copied from $XEXSAS/lib to $user_def every time you execute prisma.sh so that your old modespe.a file will be over written. This makes sure that you always add your user defined models to the newest and most up-to-date EXSAS library. Access to your user defined model is archived by checking the existence of the file modespe.exe in the directory $user_def. If the file modespe.exe exists in $user_def it will be executed, for example, by model/spectrum. Otherwise EXSAS executes its private copy of modespe.exe which it finds in $XEXSAS/exe.
| Author: Werner Becker (e-mail: web@mpe-garching.mpg.de ) / Page last modified: 18-MAY-98 |