Check Lattice Graph

After writing a new lattice definition, you will want to check that it is correct before running a real simulation on it. ALPS provides the printgraph tool for this: it reads a parameter file, builds the graph from the LATTICE (or GRAPH) it specifies — exactly the way an ALPS application would build it internally — and prints the resulting graph as <GRAPH> XML, listing every <VERTEX> and <EDGE>. Comparing this output against what you intended is a quick way to catch mistakes such as a wrong extent, a missing bond, or an incorrect boundary condition.

To run it, type:

printgraph parameter_file

parameter_file is a plain ALPS parameter file — the same format used as input to parameter2xml — so no conversion step is needed first. If no file name is given, printgraph reads the parameter file from standard input instead; if the file name ends in .xml, it is read as an XML parameter file.

For example, the parameter file

LATTICE = "square lattice"
L = 2

selects the built-in square lattice (see A Library of Lattices and Graphs) with a 2 x 2 periodic extent. Running printgraph on it produces:

<GRAPH dimension="2" vertices="4" edges="8">
  <VERTEX id="1" type="0"><COORDINATE>0 0</COORDINATE></VERTEX>
  <VERTEX id="2" type="0"><COORDINATE>0 1</COORDINATE></VERTEX>
  <VERTEX id="3" type="0"><COORDINATE>1 0</COORDINATE></VERTEX>
  <VERTEX id="4" type="0"><COORDINATE>1 1</COORDINATE></VERTEX>
  <EDGE source="1" target="2" id="1" type="0" vector="0 1"/>
  <EDGE source="1" target="3" id="2" type="0" vector="1 0"/>
  <EDGE source="2" target="1" id="3" type="0" vector="0 1"/>
  <EDGE source="2" target="4" id="4" type="0" vector="1 0"/>
  <EDGE source="3" target="4" id="5" type="0" vector="0 1"/>
  <EDGE source="3" target="1" id="6" type="0" vector="1 0"/>
  <EDGE source="4" target="3" id="7" type="0" vector="0 1"/>
  <EDGE source="4" target="2" id="8" type="0" vector="1 0"/>
</GRAPH>

Each of the 4 sites appears once as a <VERTEX>, with its Cartesian coordinates; each of the 8 bonds appears once as an <EDGE>, with periodic boundary conditions producing the wrap-around bonds (e.g. source="2" target="1") alongside the “straight” ones. For a larger or unfamiliar lattice, redirecting the output to a file (printgraph parameter_file > graph.xml) makes it easier to inspect.

For an overview of the rest of this section, see Lattice Definitions. For the LATTICE/GRAPH input parameters used to select a lattice or graph by name in a simulation, see Common Parameters. For the other ALPS documentation sections, see the General Introduction.