MetaConfigurations.jl

Define a set of configurations as a single, more abstract and comprehensive meta-configuration.

] add MetaConfigurations

Besides providing functions for manipulating configurations, MetaConfigurations.jl is also a meta package for a common API through which configuration file handlers like JSON.jl and YAML.jl are unified.

Motivation

Assume you want to describe four experiments, each of which consists of a combination of two parameters.

# experiment 1
description: "Experiment with α=0.1 and β=95%"
alpha: 0.1
beta: 95%

# experiment 2
description: "Experiment with α=0.01 and β=95%"
alpha: 0.01
beta: 95%

# experiment 3
description: "Experiment with α=0.1 and β=97.5%"
alpha: 0.1
beta: 97.5%

# experiment 4
description: "Experiment with α=0.01 and β=97.5%"
alpha: 0.01
beta: 97.5%

MetaConfigurations.jl can derive these combinations from a single, more abstract and comprehensive representation, which we call a meta-configuration:

description: "Experiment with α=$(alpha) and β=$(beta)"
alpha:
  - 0.1
  - 0.01
beta:
  - 95%
  - 97.5%

The desired list of experiments is obtained from this meta-configuration by expansions and String interpolations:

using MetaConfigurations
configurations = expand(
    parsefile("example.yml"), # read the above meta-configuration
    "alpha",
    "beta"
) # create a list of cells from the matrix spanned by alpha and beta
interpolate!.(configurations, "description") # fill in the placeholders in each description

Deriving configurations from meta-configurations

Let's take a closer look on the operations provided by this package. We have already seen the first two of them.

MetaConfigurations.expand: We can expand any property that has a vector of values, like the properties alpha and beta in the example above. Consider at first the expansion of a single vector-valued property p with length n. This expansion will result in a vector of n configurations, in each of which p has only one of its initial values. The expansion of multiple properties, like above, is taken out sequentially. By expanding properties, we transform a single, comprehensive meta-configuration into a set of configurations.

MetaConfigurations.interpolate: Interpolation substitutes all placeholders in a String property with the corresponding values of other properties in the same configuration. In the above example, we have seen how the placeholders $(alpha) and $(beta) have been replaced with the actual values of alpha and beta.

MetaConfigurations.patch: A patch defines an additional key-value pair in a copy of a configuration. For example, we might want wo create a copy of the above configurations vector in which each configuration has a fixed value for an additional property gamma:

patch.(configurations; gamma=1000)

Reading and writing configuration files

MetaConfigurations.jl is also a meta-package that unifies the APIs of JSON.jl and YAML.jl. To which backend an operation is delegated is automatically determined from the file name extension.

using MetaConfigurations

cfg = parsefile("example.yml") # read from a YAML file
save("example.json", cfg) # store it as a JSON file

By default, MetaConfigurations.jl parses files into objects of the type Dict{String,Any}. You can change this behaviour through the dicttype argument, e.g. to preserve the order of the configuration file or to use Symbol instances as keys.

using MetaConfigurations, OrderedCollections

cfg = parsefile("example.yml", dicttype=OrderedDict{Symbol, Any})

Finding properties

You can recursively find properties by their key:

# continuing the introductory example, ..
find(configurations, "description")

4-element Array{String,1}:
 "Experiment with α=0.1 and β=95%"
 "Experiment with α=0.1 and β=97.5%"
 "Experiment with α=0.01 and β=95%"
 "Experiment with α=0.01 and β=97.5%"