Package com.yahoo.searchlib.rankingexpression

Class RankingExpression

java.lang.Object
com.yahoo.searchlib.rankingexpression.RankingExpression
All Implemented Interfaces:
Serializable
public class RankingExpression extends Object implements Serializable

A ranking expression. Ranking expressions are used to calculate a rank score for a searched instance from a set of rank features.

A ranking expression wraps a expression node tree and may also optionally have a name.

The identity of a ranking expression is decided by both its name and expression tree. Two expressions which looks the same in string form are the same.

Simple usage


try {
    MapContext context = new MapContext();
    context.put("one", 1d);
    RankingExpression expression = new RankingExpression("10*if(i>35,if(i>one,if(i>=670,4,8),if(i>8000,5,3)),if(i==478,90,91))");
    double result = expression.evaluate(context);
   }
catch (ParseException e) {
    throw new RuntimeException(e);
}

Or, usage optimized for repeated evaluation of the same expression


// Members in a class living across multiple evaluations
RankingExpression expression;
ArrayContext contextPrototype;

...

// Initialization of the above members (once)
// Create reusable, gbdt optimized expression and context.
// The expression is multithread-safe while the context created is not
try {
    RankingExpression expression = new RankingExpression("10*if(i>35,if(i>one,if(i>=670,4,8),if(i>8000,5,3)),if(i==478,90,91))");
    ArrayContext contextPrototype = new ArrayContext(expression);
    ExpressionOptimizer optimizer = new ExpressionOptimizer(); // Increases evaluation speed of gbdt form expressions by 3-4x
    OptimizationReport triviaAboutTheOptimization = optimizer.optimize(expression, contextPrototype);
}
catch (ParseException e) {
    throw new RuntimeException(e);
}

...

// Execution (many)
context = contextPrototype.clone(); // If evaluation is multithreaded - skip this if execution is single-threaded
context.put("one",1d);
double result = expression.evaluate(context);
Author:
Simon Thoresen Hult, bratseth
See Also:

  • Constructor Details

    • RankingExpression

      public RankingExpression(Reader reader) throws ParseException
      Creates an anonymous ranking expression by consuming from the reader
      Throws:
      ParseException

    • RankingExpression

      public RankingExpression(String name, Reader reader) throws ParseException
      Creates a new ranking expression by consuming from the reader
      Parameters:
      name - the name of the ranking expression
      reader - the reader that contains the string to parse.
      Throws:
      ParseException - if the string could not be parsed.

    • RankingExpression

      public RankingExpression(String name, String expression) throws ParseException
      Creates a new ranking expression by consuming from the reader
      Parameters:
      name - the name of the ranking expression
      expression - the expression to parse.
      Throws:
      ParseException - if the string could not be parsed.

    • RankingExpression

      public RankingExpression(String expression) throws ParseException
      Creates a ranking expression from a string
      Parameters:
      expression - The reader that contains the string to parse.
      Throws:
      ParseException - if the string could not be parsed.

    • RankingExpression

      public RankingExpression(File file) throws ParseException
      Creates a ranking expression from a file. For convenience, the file.getName() up to any dot becomes the name of this expression.
      Parameters:
      file - the name of the file whose content to parse.
      Throws:
      ParseException - if the string could not be parsed.
      IllegalArgumentException - if the file could not be found

    • RankingExpression

      public RankingExpression(String name, ExpressionNode root)
      Creates a named ranking expression from an expression root node.

    • RankingExpression

      public RankingExpression(ExpressionNode root)
      Creates a ranking expression from an expression root node.
      Parameters:
      root - The root node.

  • Method Details

    • copy

      public RankingExpression copy()
      Returns a deep copy of this expression

    • getName

      public String getName()
      Returns the name of this ranking expression, or "" if no name is set.
      Returns:
      The name of this expression.

    • setName

      public void setName(String name)
      Sets the name of this ranking expression.
      Parameters:
      name - The name to set.

    • getRoot

      public ExpressionNode getRoot()
      Returns the root of the expression tree of this expression.
      Returns:
      The root node.

    • setRoot

      public void setRoot(ExpressionNode root)
      Sets the root of the expression tree of this expression.
      Parameters:
      root - The root node to set.

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • equals

      public boolean equals(Object obj)
      Overrides:
      equals in class Object

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • getRankProperties

      public Map<String,String> getRankProperties(SerializationContext context)
      Creates the necessary rank properties required to implement this expression.
      Parameters:
      context - context for serialization
      Returns:
      a list of named rank properties required to implement this expression

    • propertyName

      public static String propertyName(String expressionName)
      Returns the rank-property name for a given expression name.
      Parameters:
      expressionName - the expression name to mangle.
      Returns:
      the property name.

    • propertyExpressionName

      public static String propertyExpressionName(String expressionName)

    • extractScriptName

      public static String extractScriptName(String propertyName)

    • type

      public com.yahoo.tensor.TensorType type(com.yahoo.tensor.evaluation.TypeContext<Reference> context)
      Validates the type correctness of the given expression with the given context and returns the type this expression will produce from the given type context
      Throws:
      IllegalArgumentException - if this expression is not type correct in this context

    • evaluate

      public Value evaluate(Context context)
      Returns the value of evaluating this expression over the given context.
      Parameters:
      context - The variable bindings to use for this evaluation.
      Returns:
      the evaluation result.
      Throws:
      IllegalArgumentException - if there are variables which are not bound in the given map

    • from

      public static RankingExpression from(String expression)
      Creates a ranking expression from a string
      Throws:
      IllegalArgumentException - if the string is not a valid ranking expression