Add relative tolerance checks to approxEquals

Fixes holdenk#214

src/main/2.0/scala/com/holdenkarau/spark/testing/DataFrameSuiteBase.scala

@@ -146,7 +146,7 @@ trait DataFrameSuiteBaseLike extends SparkContextProvider
     * @param tol max acceptable tolerance, should be less than 1.
     */
   def assertDataFrameApproximateEquals(
-    expected: DataFrame, result: DataFrame, tol: Double) {
+    expected: DataFrame, result: DataFrame, tol: Double = 0.0, relTol: Double = 0.0) {
 
     assert(expected.schema, result.schema)
 
@@ -160,7 +160,7 @@ trait DataFrameSuiteBaseLike extends SparkContextProvider
 
       val unequalRDD = expectedIndexValue.join(resultIndexValue).
         filter{case (idx, (r1, r2)) =>
-          !DataFrameSuiteBase.approxEquals(r1, r2, tol)}
+          !DataFrameSuiteBase.approxEquals(r1, r2, tol, relTol)}
 
       assertEmpty(unequalRDD.take(maxUnequalRowsToShow))
     } finally {
@@ -178,15 +178,42 @@ trait DataFrameSuiteBaseLike extends SparkContextProvider
     rdd.zipWithIndex().map{ case (row, idx) => (idx, row) }
   }
 
-  def approxEquals(r1: Row, r2: Row, tol: Double): Boolean = {
-    DataFrameSuiteBase.approxEquals(r1, r2, tol)
+  def approxEquals(r1: Row, r2: Row, tol: Double = 0.0, relTol: Double = 0.0): Boolean = {
+    DataFrameSuiteBase.approxEquals(r1, r2, tol, relTol)
   }
 }
 
 object DataFrameSuiteBase {
+  trait WithinToleranceChecker {
+    def apply(a: Double, b: Double): Boolean
+    def apply(a: BigDecimal, b: BigDecimal): Boolean
+  }
+
+  class WithinAbsoluteToleranceChecker(tolerance: Double)
+      extends WithinToleranceChecker {
+    def apply(a: Double, b: Double): Boolean =
+      (a - b).abs <= tolerance
+    def apply(a: BigDecimal, b: BigDecimal): Boolean =
+      (a - b).abs <= tolerance
+  }
+
+  class WithinRelativeToleranceChecker(relativeTolerance: Double)
+      extends WithinToleranceChecker {
+    def apply(a: Double, b: Double): Boolean =
+      (a - b).abs / (a.abs max b.abs) <= relativeTolerance
+    def apply(a: BigDecimal, b: BigDecimal): Boolean =
+      (a - b).abs / (a.abs max b.abs) <= relativeTolerance
+  }
 
   /** Approximate equality, based on equals from [[Row]] */
-  def approxEquals(r1: Row, r2: Row, tol: Double): Boolean = {
+  def approxEquals(r1: Row, r2: Row, tol: Double = 0.0, relTol: Double = 0.0): Boolean = {
+    val withinTolerance =
+      if(tol != 0.0 || relTol == 0.0) {
+        new WithinAbsoluteToleranceChecker(tol)
+      } else {
+        new WithinRelativeToleranceChecker(relTol)
+      }
+
     if (r1.length != r2.length) {
       return false
     } else {
@@ -212,7 +239,7 @@ object DataFrameSuiteBase {
               {
                 return false
               }
-              if (abs(f1 - o2.asInstanceOf[Float]) > tol) {
+              if (!withinTolerance(f1, o2.asInstanceOf[Float])) {
                 return false
               }
 
@@ -222,18 +249,17 @@ object DataFrameSuiteBase {
               {
                 return false
               }
-              if (abs(d1 - o2.asInstanceOf[Double]) > tol) {
+              if (!withinTolerance(d1, o2.asInstanceOf[Double])) {
                 return false
               }
 
             case d1: java.math.BigDecimal =>
-              if (d1.subtract(o2.asInstanceOf[java.math.BigDecimal]).abs
-                    .compareTo(new java.math.BigDecimal(tol)) > 0) {
+              if (!withinTolerance(BigDecimal(d1), BigDecimal(o2.asInstanceOf[java.math.BigDecimal]))) {
                 return false
               }
 
             case d1: scala.math.BigDecimal =>
-              if ((d1 - o2.asInstanceOf[scala.math.BigDecimal]).abs > tol) {
+              if (!withinTolerance(d1, o2.asInstanceOf[scala.math.BigDecimal])) {
                 return false
               }
 

src/test/1.3/scala/com/holdenkarau/spark/testing/SampleDataFrameTest.scala

@@ -18,6 +18,7 @@ package com.holdenkarau.spark.testing
 
 import org.apache.spark.sql.Row
 import org.scalatest.FunSuite
+import java.math.{ BigDecimal => JBigDecimal }
 
 class SampleDataFrameTest extends FunSuite with DataFrameSuiteBase {
   val byteArray = new Array[Byte](1)
@@ -64,10 +65,10 @@ class SampleDataFrameTest extends FunSuite with DataFrameSuiteBase {
     val row6 = Row("1")
     val row6a = Row("2")
     val row7 = Row(1.toFloat)
-    val row8 = Row(new java.math.BigDecimal(1.0))
-    val row8a = Row(new java.math.BigDecimal(1.0 + 1.0E-6))
-    val row9 = Row(scala.math.BigDecimal(1.0))
-    val row9a = Row(scala.math.BigDecimal(1.0 + 1.0E-6))
+    val row8 = Row(new JBigDecimal(1.0))
+    val row8a = Row(new JBigDecimal(1.0 + 1.0E-6))
+    val row9 = Row(BigDecimal(1.0))
+    val row9a = Row(BigDecimal(1.0 + 1.0E-6))
     assert(false === approxEquals(row, row2, 1E-7))
     assert(true === approxEquals(row, row2, 1E-5))
     assert(true === approxEquals(row3, row3, 1E-5))
@@ -82,6 +83,35 @@ class SampleDataFrameTest extends FunSuite with DataFrameSuiteBase {
     assert(true === approxEquals(row9, row9a, 1.0E-6))
   }
 
+  test("dataframe approxEquals on rows with relative tolerance") {
+    import sqlContext.implicits._
+    // Use 1 / 2^n as example numbers to avoid numeric errors
+    val relTol = 0.125
+    val orig = 0.25
+    val within = orig - relTol * orig
+    val outside = within - 1.0E-4
+    def assertRelativeApproxEqualsWorksFor[T](constructor: Double => T) = {
+      assertResult(true) {
+        approxEquals(
+          Row(constructor(orig)),
+          Row(constructor(within)),
+          relTol = relTol
+        )
+      }
+      assertResult(false) {
+        approxEquals(
+          Row(constructor(orig)),
+          Row(constructor(outside)),
+          relTol = relTol
+        )
+      }
+    }
+    assertRelativeApproxEqualsWorksFor[Double](identity)
+    assertRelativeApproxEqualsWorksFor[Float](_.toFloat)
+    assertRelativeApproxEqualsWorksFor[BigDecimal](BigDecimal.apply)
+    assertRelativeApproxEqualsWorksFor[JBigDecimal](new JBigDecimal(_))
+  }
+
   test("verify hive function support") {
     import sqlContext.implicits._
     // Convert to int since old versions of hive only support percentile on