WrapRec :: Evaluation Framework for Recommender Systems

Get Started with WrapRec

Learn about the basic concepts in WrapRec


Overview

WrapRec is an open-source project, developed with C# which aims to simplify the evaluation of Recommender System algorithms. WrapRec is a configuration-based tool. All desing choices and parameters should be defined in a configuration file.

The easiest way to use WrapRec is to download the latest release, specify the details of experiments that you want to perform within a configuration file and run the WrapRec executable.

Get Started with a "Hello MovieLens" Example

MovieLens is one of the most widely-used benchmark datasets in Recommeder Systems research. Start to use WrapRec with a simple train-and-test scenario using the 100K version of this dataset.

To run the example Download the Hello MovieLens exmaple and extract it in the same folder that contains WrapRec executable. Run the example by the following command.
In Windows, you should have .Net Framework, and in Linux and Mac you should have .Net Mono installed to run WrapRec.

Windows

wraprec.exe sample.xml

Linux and Mac

mono wraprec.exe sample.xml

The example performs four simple experiment with MoviLens 100K dataset. The result of experiments will be stored in a folder results with csv format. Check WrapRec Outputs to understand more about the restuls and outputs of WrapRec.

You can start your experiments by modifying the sample configuration file. The configuration file is rather intuitive and easy to understand. Check Configuration section to undrestand the format of the configuration file in WrapRec.


WrapRec Architecture

WrapRec is designed based on the idea that for any evaluation experiment for Recommender Systems (and generally in Machine Learning), three main components should be present

Model
Defines the algorithm that is used to train and evalute Recommender System
Split
Specifies the data sources and how the data should be splitted for training and evaluation
Evaluation
Context
Defines a set of evaluators to evaluate a trained model

The overal architecture of WrapRec is summerized in the Figure below. WrapRec is not about implementation of actual algorithms for recommender systems. Instead, it provides functionalities to easily wrap exisiting algorithms into framework, to be able to perform extensive evaluation experiments in single framework.


Building Blocks in WrapRec

To perform an evaluation experiment with WrapRec, three main building blocks are required.

Model

Defines the algorithm that is used to train and evalute Recommender System

Currently WrapRec is able to wrap algorithms from two Recommender System toolkits: MyMediLite and LibFm. You can also plug your own algorithm to this framework. Check How to Extend WrapRec to learn how to extend WrapRec with your own algorithm or third party implementations.

Split

Specifies the data sources and how the data should be splitted for training and evaluation

In WrapRec data will be loaded through DataReader components. You can define in the configuration file what is the input data, what is the format and how it should be loaded. The data will be store in a DataContainer object. An Split defines, how the data in DataContainer can be splited for training and evaluation. WrapRec supports several splitting methods such as static, dynamic and Cross-Validation.

Evaluation Context

Defines a set of evaluators to evaluate a trained model

Evaluation Context is a component is WrapRec that consists of several Evaluators and store the results of evaluations that are done with Evaluator objects.


Configuration File

In WrapRec all the settings and desing choices are defined in a configuration file.

The overal format of the configuration file is defined as follow.

  • Components in the configuration file are loaded via Reflection and the parameters are dynamic. It means that you can specify the type of class and its properties and WrapRec creates the objects during runtime.
  • Parameters can have multiple values. WrapRec detects all parameters with multiple values and run multiple experiments, as many times and the catesian product of all parameters.
  • The three main components of an experiments (Model, Split and Evaluation Context) should be defined in the configuration file.


                    
                    

Experiment

In WrapRec evaluation experiments are defined in an experiment object. In the configuration file an experiment is defined in an experiment element.


                    
                        You can specify as many models and splits as you want in the experiment element.
                        For each combination of models and split WrapRec runs an evaluation experiment.
                        Models, Splits and EvalationContexts should be defined by their own elements.

                        In the experiments element, you can define as many experiment as you want.
                        experiments element is the starting point of parsing the configuration file
                        and runnig the experiments. You can specify which experiment(s) you want to run
                        using run attribute.
                    

WrapRec Output

For each experiment that you run with WrapRec, two csv files will be generated. The name of the files are [experimentId].csv and [experimentId].splits.csv. The first file contains the results of experiment (in tab separated by default) and the second file contains some statistics about the dataset and splits that is used for that experiment. These two files are stored in the path that are specified by the attribute resultsFolder. You can change the delimiter of the generated csv files using attribute delimiter="[delimiter]". WrapRec log some information when the experiments are running. You can change the verbosity of experiments using the attribute verbosity. The values can be trace (which log more details) and info.

Model

A model is defined with a model element. There are two obligatory attributes for a model element: id which is a name or id that you define for the model , and class which is a full type name (including namespace) of the model class.

Advanced hint: If the class is defined in another assembly, the path of the assembly should be prefix in the attribute class with a colon, that is, [path to assmebly]:[full type name]

In addition you can define the propeties of the model class in the sub-element parameters. Here is an example of a model definition:


                    The class specifies WrapRec wrapper class and the parameters specify the 
                    properties of the model. 
                    See detailed Documentation to see possible parameters
                    for different WrapRec models. 

                    
All parameters can have multiple values separated by comma. For each combinatio of parameters WrapRec creates an instance of the model object.

Hint: when you use a modelId in an experiment, for each combinatio of parameters one model instance will be used.

Split

An split is defined with an split element. With an split object you specify what is the source of data and how should the data be splitted into train and test sets. Using the attribute dataContainer you should specify what is the data source of the split.



                        An split can have four different types:
                        
  • Static
  • Dynamic
  • Cross-validation (cv)
  • Custom
By defualt the splits are created using the FeedbackSimpleSplit class. You can make your own split logic by defining your own custom class and use the type name in the parameter class. Your custom split class should extend class WrapRec.Data.Split. Check extending WrapRec to see how you can defined your ownd types.
The attributes trainRatios and numFolds can have multiple values (comma separated). This means that the for each combination of parameters one split object would be created.

Data

In WrapRec data are stored in a DataContainer object. The data is loaded into the DataContainer object via DataReader objects. A DataContainer should specify which DataReaders should be used to load data into it. DataReaders specify how data should be loaded.


                        


                        You can use the default reader class WrapRec.IO.CsvReader
                        to read csv data. If you are using this class there are few more parameters namely
                        hasHeader=[true|false] to indicate whether the csv has header or not
                        , delimiter=[delimiter] to specify delimiter in the csv file.
                        In addition you can specify the format of the csv file using the header=[comma separated fields] attribute.

                    

Evaluation Context

An Evaluation Context is defined with a evalContext element. An EvaluationContext object can have multiple evaluator objects that evaluate a trained model. Evaluators are defined with an evaluator element. Here is the fomrat of the evalContext element:



                        You can use multiple Evaluators in an evaluation context. evaluator
                        element has an obligatory attribute class that specifies
                        the evaluator class. Depending on the evaluator class, more parameters
                        can be used. Here is an example of an evaluation context with multiple evaluators:
                        
                        


                        Here three evaluators are used. The firs two are simple RMSE ane MAE evalutors.
                        If you want to use ranking-based evaluators, you can use class
                        WrapRec.Evaluation.RankingEvaluators. Here you can specify
                        more parameters. This evaluator measures the following metrics:

                        
  • Precision
  • Recall
  • MAP
  • MRR
  • NDCG
  • % of item coverage
You can specify what would be the source of candidate items (to generate ranked list) using the attribute candidateItemsMode. It can have one of the following values:
  • training
  • test
  • union
  • overlap
  • explicit

Extending WrapRec

You can add your own logic to WrapRec or wrap other toolkits to it. Currently WrapRec wraps two recommmender systems frameworks of LibFm and MyMediaLite. If you want to contribute on WrapRec, feel free to fork the WrapRec github repository and make a pull request.
You can also create your custom Experiment, Model, Split, DataReader and Evaluator in a different assembly and use them in the configuration file.