org.apache.pig.piggybank.evaluation.math

Class ULP

java.lang.Object

org.apache.pig.EvalFunc<java.lang.Double>

org.apache.pig.piggybank.evaluation.math.ULP

public class ULP
extends EvalFunc<java.lang.Double>

math.ULP implements a binding to the Java function Math.ulp(double). Given a single data atom it Returns the size of an ulp of the argument.

Parameters:

value - Double.

Return Value:

Double

Return Schema:

ULP_inputSchema

Example:

register math.jar;
A = load 'mydata' using PigStorage() as ( float1 );
B = foreach A generate float1, math.ULP(float1);

Author:

ajay garg

See Also:

Math.ulp(double),

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.pig.EvalFunc

EvalFunc.SchemaType

Field Summary

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

Constructors

Constructor and Description
ULP()

Method Summary

Modifier and Type	Method and Description
java.lang.Double	exec(Tuple input) java level API
java.util.List<FuncSpec>	getArgToFuncMapping() Allow a UDF to specify type specific implementations of itself.
Schema	outputSchema(Schema input) Report the schema of the output of this UDF.

Methods inherited from class org.apache.pig.EvalFunc

allowCompileTimeCalculation, finish, getCacheFiles, getInputSchema, getLoadCaster, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, getShipFiles, isAsynchronous, needEndOfAllInputProcessing, progress, setEndOfAllInput, setInputSchema, setPigLogger, setReporter, setUDFContextSignature, warn

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ULP

public ULP()

Method Detail

exec

public java.lang.Double exec(Tuple input)
                      throws java.io.IOException

java level API

Specified by:

exec in class EvalFunc<java.lang.Double>

Parameters:

input - expects a single numeric value

output - returns a single numeric value, the size of an ulp of the argument.

Returns:

result, of type T.

Throws:

java.io.IOException

outputSchema

public Schema outputSchema(Schema input)

Description copied from class: EvalFunc

Report the schema of the output of this UDF. Pig will make use of this in error checking, optimization, and planning. The schema of input data to this UDF is provided.

The default implementation interprets the OutputSchema annotation, if one is present. Otherwise, it returns null (no known output schema).

Overrides:

outputSchema in class EvalFunc<java.lang.Double>

Parameters:

input - Schema of the input

Returns:

Schema of the output

getArgToFuncMapping

public java.util.List<FuncSpec> getArgToFuncMapping()
                                             throws FrontendException

Description copied from class: EvalFunc

Allow a UDF to specify type specific implementations of itself. For example, an implementation of arithmetic sum might have int and float implementations, since integer arithmetic performs much better than floating point arithmetic. Pig's typechecker will call this method and using the returned list plus the schema of the function's input data, decide which implementation of the UDF to use.

Overrides:

getArgToFuncMapping in class EvalFunc<java.lang.Double>

Returns:

A List containing FuncSpec objects representing the EvalFunc class which can handle the inputs corresponding to the schema in the objects. Each FuncSpec should be constructed with a schema that describes the input for that implementation. For example, the sum function above would return two elements in its list:

1. FuncSpec(this.getClass().getName(), new Schema(new Schema.FieldSchema(null, DataType.DOUBLE)))
2. FuncSpec(IntSum.getClass().getName(), new Schema(new Schema.FieldSchema(null, DataType.INTEGER)))

This would indicate that the main implementation is used for doubles, and the special implementation IntSum is used for ints.

Throws:

FrontendException