Adding Support for Serpent Versions

One of the main goals for this project is to include support for more SERPENT versions. The goal of this document is to detail what steps are required in order to include support for additional SERPENT versions.


Supporting additional versions is an ongoing task. See #117 and linked issues for updates


  1. Include the version as an option in the serpentVersion setting - serpentVersion

  2. Update the Default Settings

  3. Update serpentTools/variables.yaml to include the version and any new variable groups present in the results files - New Variables

  4. If serpentTools/variables.yaml is updated, update Variable Groups using the script docs/

New Variables

As detailed in Variable Groups, serpentTools utilizes a collection of variable groups to expedite what data is extracted from results and branching files. Some versions of SERPENT may have different data, as more features are added to the code, whiles some may have the same data with different names. Variables and variable groups can be added to serpentTools/variables.yaml as sets. Since the order of the variables present in the file is not important, and we are simply interested in if a variable found in a file is in a group, the set provides a good framework for this inspection.

The basic structure of serpentTools/variables.yaml is given below for a single version:

    |- group_0
        | - variable_0
        | - variable_1
    |- group_1
         | - variable_0
         | - variable_1

There is also a base version that serves as a catch-all, as detailed in Variable Lookup Procedure.

Variables are loaded from serpentTools/variables.yaml as nested dictionaries:

variables = {
    version0: {group_0: {variable_0, variable_1, ...},
               group_1: {variable_0, variable_1, ...},
    version1: {group_0: {variable_0, variable_1, ...},
               group_1: {variable_0, variable_1, ...},

Variable Lookup Procedure

The lookup procedure for variable groups is as follows. For a specific SERPENT version V and variable group g,

  • If the variable group is explicitly declared under variables[V], then take the

    variables from variables[V][g]

  • If the group is declared under variables['base'], then

    take the variables from variables['base'][g]

  • Otherwise, raise an error

The 'base' serves to store variables that are invariant across all SERPENT versions. As the development of SERPENT progresses, it is not unlikely that the 'base' group may dwindle, as each version listed in serpentTools/variables.yaml expands.

Shared Variable Groups

For variable groups that are similar between two versions but not contained in 'base', one can take advantage of YAML anchors and aliases, implemented in PyYAML as & and * characters. An example of sharing a group between two versions this way is given below:

  parentG: !!set &parentG
    {vx0, vx1, ...}
  childG: *parentG

Loading such a file would return a dictionary like:

{parentV: {parentG: {vx0, vx1, ...}},
 childV: {childV:{vx0, vx1, ...}}}

Versions with New File Formats

In the event that a future version of SERPENT causes substantial changes to the layout of output files, such that present readers will not work, then version-specific read methods will have to be written. If/when this happens, a procedure will be developed and added here.


This is a mapping variable located in the ResultsReader parser. The variable is a nested dictionary, where the keys describe the version and the nested dictionary describes the various data blocks within the results file (_res.m).

In general the results file is divided into three main blocks: - metadata: general description of the simulation - resdata: time-dependent values, e.g. k-eff - universes: universe dependent values, such as cross-sections The mapping through the variable MapStrVersions should reflect this.

The basic mapping definition relies on the following structure:

MapStrVersions = {'2.1.29':                             # serpent version
{'meta': 'VERSION',                             # The starting keyword of the metadata block
'rslt': 'MIN_MACROXS',          # The starting keyword of the resdata block
'univ': 'GC_UNIVERSE_NAME',     # The starting keyword of the universes block
'days': 'BURN_DAYS',                    # A keyword used in Serpent to describe time, days
'burn': 'BURNUP',               # A keyword used in Serpent to describe burnup, MWd/kgU
'infxs': 'INF_',                # A prefix in Serpent used to describe infinite cross-sections
'b1xs': 'B1_',                                  # A prefix in Serpent used to describe b1 cross-sections
'varsUnc': ['MICRO_NG', 'MICRO_E', 'MACRO_NG', 'MACRO_E']}} # Only the variables that have no uncertainties in the universe block

In order to support different serpent versions, these keywords would need to be updated.