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tessl/maven-ai-catboost--catboost-spark-macros-2-13

Scala macro annotations for generating parameter getter and setter methods in CatBoost Spark ML components

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CatBoost Spark Macros

CatBoost Spark Macros provides compile-time macro annotations for automatically generating parameter getter and setter methods in Apache Spark ML components. This library eliminates boilerplate code by transforming parameter field declarations into complete getter/setter method pairs at compile time.

Package Information

  • Package Name: catboost-spark-macros_2.13
  • Package Type: maven
  • Language: Scala 2.13
  • Installation: Add to your pom.xml: 
    <dependency>
  <groupId>ai.catboost</groupId>
  <artifactId>catboost-spark-macros_2.13</artifactId>
  <version>1.2.8</version>
</dependency>

Core Imports

import ai.catboost.spark.params.macros.ParamGetterSetter

Basic Usage

import ai.catboost.spark.params.macros.ParamGetterSetter
import org.apache.spark.ml.param._

class MySparkMLComponent extends Params {
  
  // Annotate parameter declarations to auto-generate getters/setters
  @ParamGetterSetter
  final val learningRate: DoubleParam = new DoubleParam(this, "learningRate", "Learning rate for training")
  
  @ParamGetterSetter  
  final val maxDepth: IntParam = new IntParam(this, "maxDepth", "Maximum tree depth")
  
  @ParamGetterSetter
  final val features: StringArrayParam = new StringArrayParam(this, "features", "Feature column names")
}

// The macro automatically generates these methods:
// def getLearningRate: Double = $(learningRate)
// def setLearningRate(value: Double): this.type = set(learningRate, value)
// def getMaxDepth: Int = $(maxDepth)  
// def setMaxDepth(value: Int): this.type = set(maxDepth, value)
// def getFeatures: Array[String] = $(features)
// def setFeatures(value: Array[String]): this.type = set(features, value)

Capabilities

Parameter Macro Annotation

The @ParamGetterSetter annotation automatically transforms parameter field declarations into getter and setter method pairs.

@compileTimeOnly("enable macro paradise to expand macro annotations")
private[spark] class ParamGetterSetter extends StaticAnnotation

Supported Parameter Types:

// Basic parameter types
BooleanParam     → Boolean
DoubleParam      → Double  
FloatParam       → Float
IntParam         → Int
LongParam        → Long
DurationParam    → java.time.Duration

// Array parameter types  
DoubleArrayParam → Array[Double]
IntArrayParam    → Array[Int]
StringArrayParam → Array[String]

// Generic parameter types
Param[T]                    → T
EnumParam[T]                → T  
OrderedStringMapParam[T]    → java.util.LinkedHashMap[String, T]

Usage Pattern:

The annotation must be applied to parameter field declarations following this exact pattern:

@ParamGetterSetter
final val parameterName: ParameterType = new ParameterType(this, "parameterName", "description")

Generated Methods:

For each annotated parameter, the macro generates:

// Getter method - returns current parameter value
def get{CapitalizedParameterName}: ParameterValueType = $(parameterName)

// Setter method - sets parameter value and returns this for chaining  
def set{CapitalizedParameterName}(value: ParameterValueType): this.type = set(parameterName, value)

Macro Implementation

The macro transformation logic that processes annotated parameter declarations.

private[spark] object ParamGetterSetterMacro {
  /**
   * Core macro implementation method that transforms parameter declarations
   * @param c Macro context for compilation
   * @param annottees Variable arguments representing annotated expressions
   * @return Transformed code expression with generated getter/setter methods
   */
  def impl(c: whitebox.Context)(annottees: c.Expr[Any]*): c.Expr[Any]
}

Usage Examples

Basic Parameter Setup

import ai.catboost.spark.params.macros.ParamGetterSetter
import org.apache.spark.ml.param._

class CatBoostClassifier extends Params {
  
  @ParamGetterSetter
  final val iterations: IntParam = new IntParam(this, "iterations", "Number of boosting iterations")
  
  @ParamGetterSetter
  final val learningRate: DoubleParam = new DoubleParam(this, "learningRate", "Learning rate")
  
  @ParamGetterSetter
  final val catFeatures: IntArrayParam = new IntArrayParam(this, "catFeatures", "Categorical feature indices")
  
  // Generated methods are now available:
  // getIterations: Int, setIterations(value: Int): this.type
  // getLearningRate: Double, setLearningRate(value: Double): this.type  
  // getCatFeatures: Array[Int], setCatFeatures(value: Array[Int]): this.type
}

Method Chaining

val classifier = new CatBoostClassifier()
  .setIterations(1000)
  .setLearningRate(0.1)
  .setCatFeatures(Array(0, 2, 4))

// Access parameter values
val currentIterations = classifier.getIterations  // 1000
val currentRate = classifier.getLearningRate      // 0.1

Complex Parameter Types

import ai.catboost.spark.params.macros.ParamGetterSetter
import org.apache.spark.ml.param._

class AdvancedModel extends Params {
  
  @ParamGetterSetter
  final val hyperParams: OrderedStringMapParam[Double] = 
    new OrderedStringMapParam(this, "hyperParams", "Hyperparameter configuration")
  
  @ParamGetterSetter
  final val enabled: BooleanParam = new BooleanParam(this, "enabled", "Enable advanced features")
  
  // Generated methods:
  // getHyperParams: java.util.LinkedHashMap[String, Double]
  // setHyperParams(value: java.util.LinkedHashMap[String, Double]): this.type
  // getEnabled: Boolean  
  // setEnabled(value: Boolean): this.type
}

Error Handling

The macro performs compile-time validation and will abort compilation with descriptive error messages for:

  • Invalid parameter types: Unsupported parameter types not in the predefined list
  • Wrong type parameters: Generic parameters without exactly one type parameter
  • Invalid usage: Annotation used on non-parameter declarations

Example compile-time errors:

// Error: "Bad paramType: CustomParam"
@ParamGetterSetter
final val custom: CustomParam = new CustomParam(this, "custom", "desc")

// Error: "Param must have one type parameter"  
@ParamGetterSetter  
final val multi: Param[String, Int] = new Param(this, "multi", "desc")

// Error: "Annotation @ParamGetterSetter can be used only with Param declarations"
@ParamGetterSetter
val notAParam: String = "invalid"

Dependencies

The macro requires the following Scala dependencies:

  • scala.annotation.{StaticAnnotation, compileTimeOnly}
  • scala.language.experimental.macros
  • scala.reflect.macros.whitebox

Compilation Requirements

  • Macro Paradise: Requires macro paradise plugin or Scala 2.13+ for macro annotation support
  • Compilation Order: Must be compiled before dependent code that uses the generated methods
  • Runtime Removal: Uses @compileTimeOnly to ensure the annotation is removed from runtime bytecode

docs

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