[SPARK-7794] [MLLIB] update RegexTokenizer default settings

The previous default is `{gaps: false, pattern: "\\p{L}+|[^\\p{L}\\s]+"}`. The default pattern is hard to understand. This PR changes the default to `{gaps: true, pattern: "\\s+"}`. jkbradley

Author: Xiangrui Meng <meng@databricks.com>

Closes #6330 from mengxr/SPARK-7794 and squashes the following commits:

5ee7cde [Xiangrui Meng] update RegexTokenizer default settings

2 files changed, 25 insertions, 25 deletions

diff --git a/mllib/src/main/scala/org/apache/spark/ml/feature/Tokenizer.scala b/mllib/src/main/scala/org/apache/spark/ml/feature/Tokenizer.scala
index 3f7f4f96fc..31f3a1aa4c 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/feature/Tokenizer.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/feature/Tokenizer.scala
@@ -26,6 +26,8 @@ import org.apache.spark.sql.types.{ArrayType, DataType, StringType}
 /**
  * :: AlphaComponent ::
  * A tokenizer that converts the input string to lowercase and then splits it by white spaces.
+ *
+ * @see [[RegexTokenizer]]
  */
 @AlphaComponent
 class Tokenizer(override val uid: String) extends UnaryTransformer[String, Seq[String], Tokenizer] {
@@ -45,9 +47,9 @@ class Tokenizer(override val uid: String) extends UnaryTransformer[String, Seq[S
 
 /**
  * :: AlphaComponent ::
- * A regex based tokenizer that extracts tokens either by repeatedly matching the regex(default)
- * or using it to split the text (set matching to false). Optional parameters also allow filtering
- * tokens using a minimal length.
+ * A regex based tokenizer that extracts tokens either by using the provided regex pattern to split
+ * the text (default) or repeatedly matching the regex (if `gaps` is true).
+ * Optional parameters also allow filtering tokens using a minimal length.
  * It returns an array of strings that can be empty.
  */
 @AlphaComponent
@@ -71,8 +73,8 @@ class RegexTokenizer(override val uid: String)
   def getMinTokenLength: Int = $(minTokenLength)
 
   /**
-   * Indicates whether regex splits on gaps (true) or matching tokens (false).
-   * Default: false
+   * Indicates whether regex splits on gaps (true) or matches tokens (false).
+   * Default: true
    * @group param
    */
   val gaps: BooleanParam = new BooleanParam(this, "gaps", "Set regex to match gaps or tokens")
@@ -84,8 +86,8 @@ class RegexTokenizer(override val uid: String)
   def getGaps: Boolean = $(gaps)
 
   /**
-   * Regex pattern used by tokenizer.
-   * Default: `"\\p{L}+|[^\\p{L}\\s]+"`
+   * Regex pattern used to match delimiters if [[gaps]] is true or tokens if [[gaps]] is false.
+   * Default: `"\\s+"`
    * @group param
    */
   val pattern: Param[String] = new Param(this, "pattern", "regex pattern used for tokenizing")
@@ -96,7 +98,7 @@ class RegexTokenizer(override val uid: String)
   /** @group getParam */
   def getPattern: String = $(pattern)
 
-  setDefault(minTokenLength -> 1, gaps -> false, pattern -> "\\p{L}+|[^\\p{L}\\s]+")
+  setDefault(minTokenLength -> 1, gaps -> true, pattern -> "\\s+")
 
   override protected def createTransformFunc: String => Seq[String] = { str =>
     val re = $(pattern).r
diff --git a/mllib/src/test/scala/org/apache/spark/ml/feature/TokenizerSuite.scala b/mllib/src/test/scala/org/apache/spark/ml/feature/TokenizerSuite.scala
index a46d08d651..eabda089d0 100644
--- a/mllib/src/test/scala/org/apache/spark/ml/feature/TokenizerSuite.scala
+++ b/mllib/src/test/scala/org/apache/spark/ml/feature/TokenizerSuite.scala
@@ -29,35 +29,34 @@ case class TokenizerTestData(rawText: String, wantedTokens: Array[String])
 
 class RegexTokenizerSuite extends FunSuite with MLlibTestSparkContext {
   import org.apache.spark.ml.feature.RegexTokenizerSuite._
-  
+
   test("RegexTokenizer") {
-    val tokenizer = new RegexTokenizer()
+    val tokenizer0 = new RegexTokenizer()
+      .setGaps(false)
+      .setPattern("\\w+|\\p{Punct}")
       .setInputCol("rawText")
       .setOutputCol("tokens")
-
     val dataset0 = sqlContext.createDataFrame(Seq(
       TokenizerTestData("Test for tokenization.", Array("Test", "for", "tokenization", ".")),
       TokenizerTestData("Te,st. punct", Array("Te", ",", "st", ".", "punct"))
     ))
-    testRegexTokenizer(tokenizer, dataset0)
+    testRegexTokenizer(tokenizer0, dataset0)
 
     val dataset1 = sqlContext.createDataFrame(Seq(
       TokenizerTestData("Test for tokenization.", Array("Test", "for", "tokenization")),
       TokenizerTestData("Te,st. punct", Array("punct"))
     ))
+    tokenizer0.setMinTokenLength(3)
+    testRegexTokenizer(tokenizer0, dataset1)
 
-    tokenizer.setMinTokenLength(3)
-    testRegexTokenizer(tokenizer, dataset1)
-
-    tokenizer
-      .setPattern("\\s")
-      .setGaps(true)
-      .setMinTokenLength(0)
+    val tokenizer2 = new RegexTokenizer()
+      .setInputCol("rawText")
+      .setOutputCol("tokens")
     val dataset2 = sqlContext.createDataFrame(Seq(
       TokenizerTestData("Test for tokenization.", Array("Test", "for", "tokenization.")),
-      TokenizerTestData("Te,st.  punct", Array("Te,st.", "", "punct"))
+      TokenizerTestData("Te,st.  punct", Array("Te,st.", "punct"))
     ))
-    testRegexTokenizer(tokenizer, dataset2)
+    testRegexTokenizer(tokenizer2, dataset2)
   }
 }
 
@@ -67,9 +66,8 @@ object RegexTokenizerSuite extends FunSuite {
     t.transform(dataset)
       .select("tokens", "wantedTokens")
       .collect()
-      .foreach {
-        case Row(tokens, wantedTokens) =>
-          assert(tokens === wantedTokens)
-    }
+      .foreach { case Row(tokens, wantedTokens) =>
+        assert(tokens === wantedTokens)
+      }
   }
 }