jFuzzyLogic is an open source fuzzy logic library implementing industry standards to simplify fuzzy systems developments.

Downloading: Why two versions?

For most applications, you should download the full version.
The core version is used mostly on mobile applications or applications where resources are limited and graphics capabilities are not required.

Getting the source code

You can download the source code form GitHub:

git clone https://github.com/pcingola/jFuzzyLogic.git

Publications & Citing

If you are using jFuzzyLogic in academic environments, please cite our publications:

• Cingolani, Pablo, and Jesús Alcalá-Fdez. "jFuzzyLogic: a Java Library to Design Fuzzy Logic Controllers According to the Standard for Fuzzy Control Programming"

  @article{cingolanijfuzzylogic,
    title={jFuzzyLogic: a Java Library to Design Fuzzy Logic Controllers According to the Standard for Fuzzy Control Programming},
    author={Cingolani, Pablo and Alcal{\'a}-Fdez, Jes{\'u}s}
    booktitle={International Journal of Computational Intelligence Systems},
    pages={61--75},
    year={2013}
  }
  

• Cingolani, Pablo, and Jesus Alcala-Fdez. "jFuzzyLogic: a robust and flexible Fuzzy-Logic inference system language implementation." Fuzzy Systems (FUZZ-IEEE), 2012 IEEE International Conference on. IEEE, 2012.

  @inproceedings{cingolani2012jfuzzylogic,
    title={jFuzzyLogic: a robust and flexible Fuzzy-Logic inference system language implementation},
    author={Cingolani, Pablo and Alcala-Fdez, Jesus},
    booktitle={Fuzzy Systems (FUZZ-IEEE), 2012 IEEE International Conference on},
    pages={1--8},
    year={2012},
    organization={IEEE}
  }
  

Command line options.

jFuzzyLogic provides several command line options that are useful for development. Here we show some common usage examples.

Running jFuzzyLogic without any command line option will show a simple help.

java -jar jFuzzyLogic.jar


Usage: java -jar jFuzzyLogic.jar [options]
Options:
   file.fcl                      : Load FCL file and show memebership functions.
  -c file.fcl                    : Compile. Generate C++ code from FCL file (to STDOUT)
  -e file.fcl in_1 in_2 ... in_n : Load FCL file, assign inputs i_1, i_2, ..., i_n and evaluate.
  demo                           : Run a demo exmaple (tipper.fcl)

java -jar jFuzzyLogic.jar demo

java -jar jFuzzyLogic.jar myfile.fcl

java -jar jFuzzyLogic.jar -e tipper.fcl 8.5 9

FUNCITON_BLOCK tipper
  VAR_INPUT         food = 8.500000
  VAR_INPUT      service = 9.000000
  VAR_OUTPUT         tip = 24.999984
  RULE_BLOCK No1
    Support   Rule name   Rule
    0.000000  1           IF (service IS poor) OR (food IS rancid) THEN tip IS cheap;
    0.000000  2           IF service IS good THEN tip IS average;
    0.750000  3           IF (service IS excellent) AND (food IS delicious) THEN tip IS generous;

The obvious advantages of having a standard language for fuzzy systems.

Fuzzy control language (FCL) is a language defined in the IEC 61131 part 7 specification.

Note: Unfortunately the FCL specification is not freely available and you have to buy the document from IEC. But you can access a free copy of the pre-release version of the spec. here.

Obviously, having a standard language to program fuzzy systems has many benefits. Before FCL, each fuzzy logic library implementation had different ways to define membership functions, rules, etc. Most of the time you had to learn APIs which were incompatible from one system to another. Furthermore, using APIs to create systems is cumbersome and error prone.
FCL simply removes all these problems. Furthermore, FCL is quite simple to learn and most people learn the basics by taking a looks at a couple of examples.

Fuzzy control language: For an introduction to FCL, please read the pre-release specification here.

The following example is FCL code for the classic "tipper" problem. The problem is how to calculate the tip in a restaurant (obviously, this is a toy example of a trivial problem. equivalent to a "hello world!" example in other programming languages):

You can download this file here.

/*
	Example: A tip calculation FIS (fuzzy inference system)
	Calculates tip based on 'service' and 'food'

									Pablo Cingolani 
*/

FUNCTION_BLOCK tipper	// Block definition (there may be more than one block per file)

// Define input variables
VAR_INPUT				
	service : REAL;
	food : REAL;
END_VAR

// Define output variable
VAR_OUTPUT				
	tip : REAL;
END_VAR

// Fuzzify input variable 'service': {'poor', 'good' , 'excellent'}
FUZZIFY service			
	TERM poor := (0, 1) (4, 0) ; 
	TERM good := (1, 0) (4,1) (6,1) (9,0);
	TERM excellent := (6, 0) (9, 1);
END_FUZZIFY

// Fuzzify input variable 'food': { 'rancid', 'delicious' }
FUZZIFY food			
	TERM rancid := (0, 1) (1, 1) (3,0) ;
	TERM delicious := (7,0) (9,1);
END_FUZZIFY

// Defzzzify output variable 'tip' : {'cheap', 'average', 'generous' }
DEFUZZIFY tip			
	TERM cheap := (0,0) (5,1) (10,0);
	TERM average := (10,0) (15,1) (20,0);
	TERM generous := (20,0) (25,1) (30,0);
	METHOD : COG;		// Use 'Center Of Gravity' defuzzification method
	DEFAULT := 0;		// Default value is 0 (if no rule activates defuzzifier)
END_DEFUZZIFY

// Inference rules
RULEBLOCK No1
	AND : MIN;	// Use 'min' for 'and'
	ACT : MIN;	// Use 'min' activation method
	ACCU : MAX;	// Use 'max' accumulation method

	RULE 1 : IF service IS poor OR food IS rancid THEN tip IS cheap;
	RULE 2 : IF service IS good THEN tip IS average; 
	RULE 3 : IF service IS excellent AND food IS delicious THEN tip IS generous;
END_RULEBLOCK

END_FUNCTION_BLOCK

java -jar jFuzzyLogic.jar tipper.fcl

Step by step explanation

• First you define each FUNCTION_BLOCK (there may be more than one in each file)
  

   FUNCTION_BLOCK tipper 

  
  
• Then input and output variables are defined.
  Note: Even though IEC-61131 defines several data types, the only variable type supported is REAL, which is the only one needed for fuzzy logic applications.
  

  VAR_INPUT
      service : REAL;
      food : REAL;
  END_VAR
  
  VAR_OUTPUT
      tip : REAL;
  END_VAR
  

  
  
• Next we define how each input variable is fuzzified is defined in FUZZIFY block. In each block we define one or more TERMs (also called LinguisticTerms). Each term is composed by a name and a membership function. E.g.:
  

  FUZZIFY service
      TERM poor := (0, 1) (4, 0) ; 
      TERM good := (1, 0) (4,1) (6,1) (9,0);
      TERM excellent := (6, 0) (9, 1);
  END_FUZZIFY
  

  
  In this lines we define how variable service will be fuzzified. Three terms are used, for instance term poor uses a piece-wise linear membership function defined by points (x0, y0) = (0, 1) and (x1, y1) = (4, 0)
  
  
  
  Similarly, we define food membership functions:
  

  FUZZIFY food
      TERM rancid := (0, 1) (1, 1) (3,0) ;
      TERM delicious := (7,0) (9,1);
  END_FUZZIFY
  

  
  
  
• Output variables are defuzzified to get a 'real' output number. Defuzzifiers are defined in DEFUZZIFY blocks. Linguistic terms (or simply terms) are defined just like in FUZZIFY blocks.

  DEFUZZIFY tip
      TERM cheap := (0,0) (5,1) (10,0);
      TERM average := (10,0) (15,1) (20,0);
      TERM generous := (20,0) (25,1) (30,0);
  

  
  
  
  
  Next, we state that 'Center of gravity' as defuzzifier method.

   METHOD : COG; 

  We also use '0' as default value, i.e. the value use when no rule activates this variable.

   DEFAULT := 0; 

• At this point we are ready to define the rules. This is done using a RULEBLOCK. First we must define some parameters. Use 'min' for 'and' (implicitly uses 'max' for 'or' to fulfill DeMorgan's Law).

  RULEBLOCK No1
      AND : MIN;
  

  Use 'min' activation method

   ACT : MIN; 

  Use 'maximum' as accumulation method.

   ACCU : MAX; 

  And now define some fuzzy rules

      RULE 1 : IF service IS poor OR food IS rancid THEN tip IS cheap;
      RULE 2 : IF service IS good THEN tip IS average; 
      RULE 3 : IF service IS excellent AND food IS delicious THEN tip is generous;
  

  Ok, that's it, you've got a fuzzy controller!

Here we show some details on jFuzzyLogic's structure as well as some basic FCL definitions.

How this package works and how classes are organized is briefly explained here.

• A fuzzy inference system (FIS) is composed by one or more FuncionBlock class, like in FCL. E.g.:

  FUNCTION_BLOCK functionBlock1
  ...
  END_FUNCTION_BLOCK
  
  FUNCTION_BLOCK functionBlock2
  ...
  END_FUNCTION_BLOCK
  

• Each FuncionBlock is composed by one or more RuleBlock class and some Variables, as well as Fuzzyfiers and Defuzzifiers. Again, like in FCL, e.g.:

  FUNCTION_BLOCK functionBlockName
  VAR_INPUT
  ...
  END_VAR
  
  VAR_OUTPUT
  ...
  END_VAR
  
  FUZZIFY inputVariable
  ...
  END_FUZZIFY
  
  DEFUZZIFY outputVariable
  ...
  END_DEFUZZIFY
  
  RULEBLOCK No1
  ...
  END_RULEBLOCK
  
  END_FUNCTION_BLOCK
  

• Each Rule class is composed by an antecedent (IF part) and a consequent (THEN part), e.g.:
  

  RULE 1 : IF service IS poor OR food IS rancid THEN tip IS cheap;
  

  • Antecedent: "service IS poor OR food IS rancid"
  • Consequent: "tip IS cheap". Note that there may be more than one consequent.
  • A rule implication (or activation) method can be defined (althought FCL does not allow different implication method for each rule, it can be defined at RULEBLOCK level). e.g.: ACT : MIN; // Use 'min' activation method

• Consequents are a 'collection' of RuleTerms classes (e.g. "tip IS cheap" is a RuleTerm)

• An Antecedent is represented by a RuleExpression class. A RuleExpression is just two terms connected by one RuleConnectionMethod (rule conectors are 'AND', 'OR' and 'NOT')
  e.g.: service IS poor OR food IS rancid
  
  • First term: "service IS poor"
  • Second term: "food IS rancid"
  • RuleConnectionMethod is 'OR'
  
  Note: Each term can be either a RuleTerm or a RuleExpression, this definition is recursive, so arbitrarily complex expressions can be created.

• Each RuleTerm is defined by a Variable and a LinguisticTermName. e.g.: service IS poor
  • Variable: service
  • LinguisticTermName: 'poor'
  • Connector: 'IS'
  It can also be 'negated' e.g.: service IS NOT excellent
  

• Each Variable has a name and some LinguisticTerms e.g.: For an input variable:

  FUZZIFY service            // Fuzzify input variable 'service': {'poor', 'good' , 'excellent'}
      TERM poor := (0, 1) (4, 0) ; 
      TERM good := (1, 0) (4,1) (6,1) (9,0);
      TERM excellent := (6, 0) (9, 1);
  END_FUZZIFY
  

  e.g.: For an output variable:

  DEFUZZIFY tip            // Defzzzify output variable 'tip' : {'cheap', 'average', 'generous' }
      TERM cheap := (0,0) (5,1) (10,0);
      TERM average := (10,0) (15,1) (20,0);
      TERM generous := (20,0) (25,1) (30,0);
      METHOD : COG;        // Use 'Center Of Gravity' defuzzification method
      DEFAULT := 0;        // Default value is 0 (if no rule activates defuzzifier)
  END_DEFUZZIFY
  

  As you can see, for an output variable you need to specify an accumulation (or RuleAgrregationMethod) and a Defuzzifier. e.g.:

  ACCU : MAX;          // Use 'max' accumulation method
  METHOD : COG;        // Use 'Center Of Gravity' defuzzification method
  

jFuzzyLogic provides convenient extensions to easily define membership functions.

Membership functions are broadly divided into two sub classes: continuous and discrete. One variable can only have either continuous or discrete membership functions.

Membership functions

• Triangular: trian min mid max

  FUZZIFY inVar2
    TERM poor := trian 0 2.5 5;
    TERM good := trian 2.5 5 7.5;
    TERM excellent := trian 5 7.5 10;
  END_FUZZIFY
  

  
  
  
• Trapetzoidal: trape min midLow midHigh max

  FUZZIFY inVar3
    TERM poor := trape 0 2 3 4;
    TERM good := trape 3 4 5 6;
    TERM excellent := trape 5 6 7 8;
  END_FUZZIFY
  

  
  
  
• Gauss: gauss mean stdev

  FUZZIFY inVar5
    TERM poor := gauss 2 2;
    TERM good := gauss 5 2;
    TERM excellent := gauss 8 2;
  END_FUZZIFY
  

  
  
  
• Generalized bell: gbell a b mean

  FUZZIFY inVar4
    TERM poor := gbell 2 4 2;
    TERM good := gbell 2 4 5;
    TERM excellent := gbell 2 4 8;
  END_FUZZIFY
  

  
  
  
• Sigmoidal: sigm gain center

  FUZZIFY inVar6
    TERM poor := sigm -4 3;
    TERM good := sigm 4 7;
  END_FUZZIFY
  

  
  
  
• Singleton: just one number (where singleton membership is 1)

  FUZZIFY inVar7
    TERM poor := 2;
    TERM good := 5;
    TERM excellent := 8;
  END_FUZZIFY
  

  
  
  
• Piece-wise linear: (x_1, y_1) (x_2, y_2) .... (x_n, y_n)

  FUZZIFY inVar1
    TERM poor := (0,1) (2, 1) (4, 0) ; 
    TERM good := (1, 0) (2, 0.5) (3, 0.7) (4,1) (4.5, 1) (5, 0.6) 
                        (6, 0.3) (7, 0.3) (8, 0.8) (9, 0.8) (10,0);
    TERM excellent := (6, 0) (9, 1) (10,1);
  END_FUZZIFY
  

  
  
  

Running FCL code from your Java code is very easy.

This is a simple Java code used to load a fuzzy inference system (FIS), this code available at TestTipper.java

package net.sourceforge.jFuzzyLogic.test;

import net.sourceforge.jFuzzyLogic.FIS;
import net.sourceforge.jFuzzyLogic.rule.FuzzyRuleSet;

/**
 * Test parsing an FCL file
 * @author pcingola@users.sourceforge.net
 */
public class TestTipper {
    public static void main(String[] args) throws Exception {
        // Load from 'FCL' file
        String fileName = "fcl/tipper.fcl";
        FIS fis = FIS.load(fileName,true);

        // Error while loading?
        if( fis == null ) { 
            System.err.println("Can't load file: '" + fileName + "'");
            return;
        }

        // Show 
        JFuzzyChart.get().chart(functionBlock);

        // Set inputs
        fis.setVariable("service", 3);
        fis.setVariable("food", 7);

        // Evaluate
        fis.evaluate();

        // Show output variable's chart
        Variable tip = functionBlock.getVariable("tip");
        JFuzzyChart.get().chart(tip, tip.getDefuzzifier(), true);

        // Print ruleSet
        System.out.println(fis);
    }
}

• FIS stands for Fuzzy Inference System and it is how the IEC norm refers to whatever you put in an FCL file. So in order to load an FCL file, we use FIS.load(fileName) function.
  

  String fileName = "fcl/tipper.fcl";
  FIS fis = FIS.load(fileName,true);
  

• If an error is detected when loading or parsing the FCL file FIS.load() returns null.

  if( fis == null ) { // Error while loading?
    System.err.println("Can't load file: '" + fileName + "'");
    return;
  }
  

• Now we can plot all variables in the FIZ (each LinguisticTerm in each Variable in the FUNCTION_BLOCK). This might be useful when you are debugging your code.

  JFuzzyChart.get().chart(functionBlock);
  

  And we get the following images:
  

  

  

• In order to make actual calculations and run the FIS, we must setting the input variables

  fis.setVariable("service", 3);
  fis.setVariable("food", 7);
  

• Now we can run the system

  fis.evaluate();
  

• If we want to know the system's output we can read the output variable's values (in this case there's only one output variable 'tip')

  Variable tip = functionBlock.getVariable("tip");
  JFuzzyChart.get().chart(tip, tip.getDefuzzifier(), true);
  

• We can also plot output's defuzzifier

  fis.getVariable("tip").chartDefuzzifier(true);
  

  
  
• And, of course, we can print the FIS

  System.out.println(fis);
  

Obtaining the system's output

public class TestTipper {
  public static void main(String[] args) throws Exception {
    FIS fis = FIS.load("fcl/tipper.fcl", true); // Load from 'FCL' file
    fis.setVariable("service", 3); // Set inputs
    fis.setVariable("food", 7);
    fis.evaluate(); // Evaluate

    // Show output variable
    System.out.println("Output value:" + fis.getVariable("tip").getValue()); 
  }
}

Rule usage

package net.sourceforge.jFuzzyLogic;
import net.sourceforge.jFuzzyLogic.rule.Rule;
public class Zzz {

  public static void main(String[] args) throws Exception {
    FIS fis = FIS.load("fcl/tipper.fcl", true); // Load from 'FCL' file
    fis.setVariable("service", 3); // Set inputs
    fis.setVariable("food", 7);
    fis.evaluate(); // Evaluate
    System.out.println("Output value:" + fis.getVariable("tip").getValue()); // Show output variable

    // Show each rule (and degree of support)
    for( Rule r : fis.getFunctionBlock("tipper").getFuzzyRuleBlock("No1").getRules() )
      System.out.println(r);
  }
}

Output value:11.701603788948043
1       (0.25)  if (service IS poor) OR (food IS rancid) then tip IS cheap [weight: 1.0]
2       (0.6666666666666666)    if service IS good then tip IS average [weight: 1.0]
3       (0.0)   if (service IS excellent) AND (food IS delicious) then tip IS generous [weight: 1.0]

Adding rules programatically

//  RULE 3 : IF ((service IS good) OR (service IS excellent)) AND food IS delicious THEN tip is generous;
Rule rule3 = new Rule("Rule3", ruleBlock);

RuleTerm term1 = new RuleTerm(service, "good", false);
RuleTerm term2 = new RuleTerm(service, "excellent", false);
RuleTerm term3 = new RuleTerm(food, "delicious", false);

RuleExpression antecedentOr = new RuleExpression(term1, term2, new RuleConnectionMethodOrMax());
RuleExpression antecedentAnd = new RuleExpression(antecedentOr, term3, new RuleConnectionMethodAndMin());

rule3.setAntecedents(antecedentAnd);
rule3.addConsequent(tip, "generous", false);
ruleBlock.add(rule3);

IF (var1 IS low) AND ( (var2 IS medium) AND (var3 IS high) ) THEN ....

This section shows how to add jFuzzyLogic as a library in your Java projects.

In order to use jFuzzyLogic in your projects, you must add jFuzzyLogic.jar as one of your JAR files (libraries). This is done like you'd do it with any other JAR file. Since this is a basic Java programming skill, so I won't get into many details.

Full example project: Here, you can download a ZIP file with a sample Eclipse project that uses jFuzzyLogic.

This video shows how to create a Java project that uses jFuzzyLogic using the Eclipse IDE.
Note: The Java code is copied from TestTipper.java and the FCL code is from tipper.fcl file.

We provide a convenient Eclipse plug-in to help developing FCL programs.

The Eclipse plug-in for FCL files provides some interesting features: syntax coloring, auto-completion, outline, quick outline, etc. Some features shown in this image (click to enlarge)

Eclipse plug-in install instructions:

• Open Eclipse
• Click on the menu Help -> Install new software you'll see the software update window
• Click on Add
  
• Name: jFuzzyLogicUpdateSite
  
• Location: http://jfuzzylogic.sourceforge.net/eclipse/
  
• Click OK an follow the instructions.
  

• Some required dependencies will also be intalled (Xtext)
  
• You will have to restart eclipse after installing this plugin
  

Eclipse plug-in feature examples

jFuzzyLogic can compile FCL into C++ code.

A built in compiler allows to compiler FCL code into C++. For instance, by simply running the following command, we can create a C++ program that has the same functionality as the FCL program:

java -jar jFuzzyLogic.jar -c tipper.fcl > tipper.cpp

jFuzzyLogic provides a parameter optimization framework, allowing to learn or refine fuzzy parameters using machine learning algorithms.

//---
// Load FIS (Fuzzy Inference System)
//---
FIS fis = FIS.load("fcl/qualify.fcl");
RuleBlock ruleBlock = fis.getFunctionBlock().getRuleBlock();

//---
// Create a list of parameter to optimize
//---
ArrayList parameterList = new ArrayList();

// Add variables. 
// Note: Fuzzy sets' parameters for these 
// variables will be optimized
Parameter.parameterListAddVariable(parameterList
                                    , fis.getVariable("scoring"));
Parameter.parameterListAddVariable(parameterList
                                    , fis.getVariable("credLimMul"));

// Add every rule's weight
for( Rule rule = ruleBlock ) 
    Parameter.parameterListAddRule(parameterList, rule);

//---
// Create an error function to be 
// optimzed (i.e. minimized)
//---
ErrorFunctionQualify errorFunction = new ErrorFunctionQualify();

//---
// Optimize (using 'Delta jump optimization')
//---
OptimizationDeltaJump optimizationDeltaJump = 
        new OptimizationDeltaJump(ruleBlock
                , errorFunction, parameterList);

// Number optimization of iterations
optimizationDeltaJump.setMaxIterations(20);

optimizationDeltaJump.optimize(true);

public class ErrorFunctionQualify extends ErrorFunction {
    public double evaluate(RuleBlock ruleBlock) {
        double error;
        // Calculate your desired error here...
        return error;
    }
}