Appendix D XML output

The FHI-aims can print results of the calculations in an XML format. This functionality is provided by the xml_write module. The module is quite general and capable of printing any XML, but also has convenient functions for printing scalars, vectors, matrices and $n$-dimensional arrays. The formatting of the data in the XML elements is both human-readable and machine-readable. The obvious advantage is that such an output from the code is extremely easy and fast to parse.

There are two ways how the XML module can be used. There is a global XML file which can be turned on with xml_file <filename> in control.in. Printing to this file is as simple as loading the module and calling one of its routines. Note however that if the block of code that prints to this global file calls another code also printing to the global file, the XML output of these two codes might get intertwined, resulting in a valid but nonsensical XML file.

A second way how to use the XML module is to create a new “local” XML file with the open_xml_file routine and use that one by calling the module printing routines with the optional argument file=<xml_file_instance>.