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<h2>
CLAWPACK Sample Code
</h2>

Variable-coefficient traffic flow model.  The flux function is
  f(q,x) = u(x)*q*(1-q)
where the "speed limit" u(x) varies with x. 
It's value in cell i is stored in aux(i,1) (see setaux.f).

Here a Riemann problem is solved with 
   u(x) = 2 for x<0
   u(x) = 1 for x>0

The initial data is set in qinit.f.   
Set ql to 0.13 for Figure 16.9
Set ql to 0.2 for Figure 16.10

The method used is based on splitting the flux difference into f-waves Z
as described in Section 15.5 and implemented in rp1trvfw.f.

Note that this requires a modified routine step1fw.f in place of the library
routine step1.f in order to implement the modified wave-propagation
algorithm.

The transonic rarefaction case is very sensitive to the flux splitting used.
The approach taken in rp1trvfw.f gives the correct solution for this case
but has not been extensively tested...

    
Example [book/chap16/vctraffic]
to accompany the book <br> &nbsp;&nbsp;
  [www.clawpack.org/book.html Finite Volume Methods for Hyperbolic Problems]
  by R. J. LeVeque.

Converted to [www.clawpack.org Clawpack 4.6] form in 2011.
        
<h4>
Plots of results
</h4>
After running this code and creating plots via "make .plots", you should be
able to view the plots in [link: _plots/_PlotIndex.html].


<h4>
Fortran files
</h4>

<dl>
<dt>[code: Makefile]
<dd> Determines which version of fortran files
are used when compiling the code with make and specifies where output and
plots should be directed.  Type "make .help" at the Unix prompt for options.

<dt>[code: driver.f]
<dd>
The driver routine allocates storage and then calls the main Clawpack
routine.

<dt>[code: setprob.f]
<dd>
A routine by this name is called by the library routine
[clawcode: clawpack/1d/lib/claw1ez.f]
and is generally used to set any values needed for the specific problem
being solved.
    
    
<dt>[code: rp1.f]
<dd>
This is the Riemann solver, which takes the $q$ values stored in the
arrays <tt>ql</tt> and <tt>qr</tt> and returns the waves in the array
<tt>wave</tt> and speeds in the array <tt>s</tt> that result in solving the
Riemann problem at each cell interface, and the fluctuations <tt>amdq</tt>
and <tt>apdq</tt>.  See [claw:doc/rp1.html] for more information about 1d
Riemann solvers.
         
<dt>[code: qinit.f]
<dd>
This subroutine sets the initial data at time $t=0$.

</dl>

<h4>
Python files
</h4>
<dl>

<dt>[code: setrun.py]
<dd> This file contains a function that
specifies what run-time parameters will be used.

Some parameters that you might want to modify are described in the
[www.clawpack.org/doc.html documentation].

<dt>[code: setplot.py]
<dd> This file contains a function that
specifies what plots will be done and
sets various plotting parameters.

</dl>


<h4>
Data files
</h4>
<font color='red'>Warning:</font> These files are generally changed
when setting up a run, usually in [code: setrun.py].

<dl>
<dt>[code: claw.data]
<dd> This file contains a number of
parameter values that are used by CLAWPACK.
The values in this file are read by the library routine
[clawcode: clawpack/1d/lib/claw1ez.f].


<dt> [code: setprob.data]
<dd> This file may contain various
parameters used in setting the initial conditions or otherwise setting up
the problem.


</dl>

<h4>Library routines</h3>

In addition to the Fortran routines in this library, several library
routines from [claw:clawpack/1d/lib] are used.  See the [code: Makefile]
to determine which ones are used.

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