tla.xmds

XMDS is a code generator that integrates equations. You write them down in human readable form in a

<?xml version="1.0"?>
<!--Two Level Atom Example simulation to illustrate a cross propagating field-->

<!-- $Id: tla.xmds,v 1.9 2004/07/14 06:37:05 joehope Exp $ -->

<!--  Copyright (C) 2000-2004                                           -->
<!--                                                                    -->
<!--  Code contributed by Greg Collecutt, Joseph Hope and Paul Cochrane -->
<!--                                                                    -->
<!--  This file is part of xmds.                                        -->
<!--                                                                    -->
<!--  This program is free software; you can redistribute it and/or     -->
<!--  modify it under the terms of the GNU General Public License       -->
<!--  as published by the Free Software Foundation; either version 2    -->
<!--  of the License, or (at your option) any later version.            -->
<!--                                                                    -->
<!--  This program is distributed in the hope that it will be useful,   -->
<!--  but WITHOUT ANY WARRANTY; without even the implied warranty of    -->
<!--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the     -->
<!--  GNU General Public License for more details.                      -->
<!--                                                                    -->
<!--  You should have received a copy of the GNU General Public License -->
<!--  along with this program; if not, write to the Free Software       -->
<!--  Foundation, Inc., 59 Temple Place - Suite 330, Boston,            -->
<!--  MA  02111-1307, USA.                                              -->

<simulation>

  <name>tla</name>

  <author>Unknown Author</author>
  <description>
    Two level atom example simulation.  Illustrates a
    cross-propagating field.
  </description>

  <!-- Global system parameters and functionality -->
  <prop_dim>z</prop_dim>

  <!-- Global variables for the simulation -->
  <globals>
  <![CDATA[
    const double g  = 1;
    const double t0 = 1;
  ]]>
  </globals>

  <!-- Field to be integrated over -->
  <field>
    <dimensions>   t    </dimensions>
    <lattice>     100   </lattice>
    <domains>  (-10,15) </domains>
    <samples>1 0</samples>

    <vector>
      <name>main</name>
      <type>double</type>
      <components>E</components>
      <![CDATA[
        E = 2/t0/cosh(t/t0);
      ]]>
    </vector>

    <vector>
      <name>cross</name>
      <type>double</type>
      <components>P N</components>
      <![CDATA[
        P =  0;
	N = -1;
      ]]>
    </vector>
  </field>

  <!-- The sequence of integrations to perform -->
  <sequence>
    <integrate>
      <algorithm>RK4EX</algorithm>
      <interval>4</interval>
      <lattice>50</lattice>
      <samples>50 50</samples>
      <vectors>main cross</vectors>
      <![CDATA[
        dE_dz =  g*P;
      ]]>
      <cross_propagation>
        <vectors>cross</vectors>
        <prop_dim>t</prop_dim>
	<![CDATA[
	  dP_dt =  E*N;
	  dN_dt = -E*P;
	]]>
      </cross_propagation>
    </integrate>
  </sequence>

  <!-- The output to generate -->
  <output format="ascii" precision="double">
    <group>
      <sampling>
        <lattice>50</lattice>
        <moments>pow_dens</moments>
	<![CDATA[
	  pow_dens = E*E;
	]]>
      </sampling>
    </group>

    <group>
      <sampling>
        <vectors>main cross</vectors>
        <lattice>50</lattice>
        <moments>P_out N_out</moments>
	<![CDATA[
	  P_out = P;
	  N_out = N;
	]]>
      </sampling>
      </group>
  </output>

</simulation>