[SPARK-20047][FOLLOWUP][ML] Constrained Logistic Regression follow up

## What changes were proposed in this pull request?
Address some minor comments for #17715:
* Put bound-constrained optimization params under expertParams.
* Update some docs.

## How was this patch tested?
Existing tests.

Author: Yanbo Liang <[email protected]>

Closes #17829 from yanboliang/spark-20047-followup.

Author: yanboliang

mllib/src/main/scala/org/apache/spark/ml/classification/LogisticRegression.scala

@@ -183,14 +183,15 @@ private[classification] trait LogisticRegressionParams extends ProbabilisticClas
    * The bound matrix must be compatible with the shape (1, number of features) for binomial
    * regression, or (number of classes, number of features) for multinomial regression.
    * Otherwise, it throws exception.
+   * Default is none.
    *
-   * @group param
+   * @group expertParam
    */
   @Since("2.2.0")
   val lowerBoundsOnCoefficients: Param[Matrix] = new Param(this, "lowerBoundsOnCoefficients",
     "The lower bounds on coefficients if fitting under bound constrained optimization.")
 
-  /** @group getParam */
+  /** @group expertGetParam */
   @Since("2.2.0")
   def getLowerBoundsOnCoefficients: Matrix = $(lowerBoundsOnCoefficients)
 
@@ -199,44 +200,47 @@ private[classification] trait LogisticRegressionParams extends ProbabilisticClas
    * The bound matrix must be compatible with the shape (1, number of features) for binomial
    * regression, or (number of classes, number of features) for multinomial regression.
    * Otherwise, it throws exception.
+   * Default is none.
    *
-   * @group param
+   * @group expertParam
    */
   @Since("2.2.0")
   val upperBoundsOnCoefficients: Param[Matrix] = new Param(this, "upperBoundsOnCoefficients",
     "The upper bounds on coefficients if fitting under bound constrained optimization.")
 
-  /** @group getParam */
+  /** @group expertGetParam */
   @Since("2.2.0")
   def getUpperBoundsOnCoefficients: Matrix = $(upperBoundsOnCoefficients)
 
   /**
    * The lower bounds on intercepts if fitting under bound constrained optimization.
    * The bounds vector size must be equal with 1 for binomial regression, or the number
    * of classes for multinomial regression. Otherwise, it throws exception.
+   * Default is none.
    *
-   * @group param
+   * @group expertParam
    */
   @Since("2.2.0")
   val lowerBoundsOnIntercepts: Param[Vector] = new Param(this, "lowerBoundsOnIntercepts",
     "The lower bounds on intercepts if fitting under bound constrained optimization.")
 
-  /** @group getParam */
+  /** @group expertGetParam */
   @Since("2.2.0")
   def getLowerBoundsOnIntercepts: Vector = $(lowerBoundsOnIntercepts)
 
   /**
    * The upper bounds on intercepts if fitting under bound constrained optimization.
    * The bound vector size must be equal with 1 for binomial regression, or the number
    * of classes for multinomial regression. Otherwise, it throws exception.
+   * Default is none.
    *
-   * @group param
+   * @group expertParam
    */
   @Since("2.2.0")
   val upperBoundsOnIntercepts: Param[Vector] = new Param(this, "upperBoundsOnIntercepts",
     "The upper bounds on intercepts if fitting under bound constrained optimization.")
 
-  /** @group getParam */
+  /** @group expertGetParam */
   @Since("2.2.0")
   def getUpperBoundsOnIntercepts: Vector = $(upperBoundsOnIntercepts)
 
@@ -256,7 +260,7 @@ private[classification] trait LogisticRegressionParams extends ProbabilisticClas
     }
     if (!$(fitIntercept)) {
       require(!isSet(lowerBoundsOnIntercepts) && !isSet(upperBoundsOnIntercepts),
-        "Pls don't set bounds on intercepts if fitting without intercept.")
+        "Please don't set bounds on intercepts if fitting without intercept.")
     }
     super.validateAndTransformSchema(schema, fitting, featuresDataType)
   }
@@ -393,31 +397,31 @@ class LogisticRegression @Since("1.2.0") (
   /**
    * Set the lower bounds on coefficients if fitting under bound constrained optimization.
    *
-   * @group setParam
+   * @group expertSetParam
    */
   @Since("2.2.0")
   def setLowerBoundsOnCoefficients(value: Matrix): this.type = set(lowerBoundsOnCoefficients, value)
 
   /**
    * Set the upper bounds on coefficients if fitting under bound constrained optimization.
    *
-   * @group setParam
+   * @group expertSetParam
    */
   @Since("2.2.0")
   def setUpperBoundsOnCoefficients(value: Matrix): this.type = set(upperBoundsOnCoefficients, value)
 
   /**
    * Set the lower bounds on intercepts if fitting under bound constrained optimization.
    *
-   * @group setParam
+   * @group expertSetParam
    */
   @Since("2.2.0")
   def setLowerBoundsOnIntercepts(value: Vector): this.type = set(lowerBoundsOnIntercepts, value)
 
   /**
    * Set the upper bounds on intercepts if fitting under bound constrained optimization.
    *
-   * @group setParam
+   * @group expertSetParam
    */
   @Since("2.2.0")
   def setUpperBoundsOnIntercepts(value: Vector): this.type = set(upperBoundsOnIntercepts, value)
@@ -427,28 +431,40 @@ class LogisticRegression @Since("1.2.0") (
       numFeatures: Int): Unit = {
     if (isSet(lowerBoundsOnCoefficients)) {
       require($(lowerBoundsOnCoefficients).numRows == numCoefficientSets &&
-        $(lowerBoundsOnCoefficients).numCols == numFeatures)
+        $(lowerBoundsOnCoefficients).numCols == numFeatures,
+        "The shape of LowerBoundsOnCoefficients must be compatible with (1, number of features) " +
+          "for binomial regression, or (number of classes, number of features) for multinomial " +
+          "regression, but found: " +
+          s"(${getLowerBoundsOnCoefficients.numRows}, ${getLowerBoundsOnCoefficients.numCols}).")
     }
     if (isSet(upperBoundsOnCoefficients)) {
       require($(upperBoundsOnCoefficients).numRows == numCoefficientSets &&
-        $(upperBoundsOnCoefficients).numCols == numFeatures)
+        $(upperBoundsOnCoefficients).numCols == numFeatures,
+        "The shape of upperBoundsOnCoefficients must be compatible with (1, number of features) " +
+          "for binomial regression, or (number of classes, number of features) for multinomial " +
+          "regression, but found: " +
+          s"(${getUpperBoundsOnCoefficients.numRows}, ${getUpperBoundsOnCoefficients.numCols}).")
     }
     if (isSet(lowerBoundsOnIntercepts)) {
-      require($(lowerBoundsOnIntercepts).size == numCoefficientSets)
+      require($(lowerBoundsOnIntercepts).size == numCoefficientSets, "The size of " +
+        "lowerBoundsOnIntercepts must be equal with 1 for binomial regression, or the number of " +
+        s"classes for multinomial regression, but found: ${getLowerBoundsOnIntercepts.size}.")
     }
     if (isSet(upperBoundsOnIntercepts)) {
-      require($(upperBoundsOnIntercepts).size == numCoefficientSets)
+      require($(upperBoundsOnIntercepts).size == numCoefficientSets, "The size of " +
+        "upperBoundsOnIntercepts must be equal with 1 for binomial regression, or the number of " +
+        s"classes for multinomial regression, but found: ${getUpperBoundsOnIntercepts.size}.")
     }
     if (isSet(lowerBoundsOnCoefficients) && isSet(upperBoundsOnCoefficients)) {
       require($(lowerBoundsOnCoefficients).toArray.zip($(upperBoundsOnCoefficients).toArray)
-        .forall(x => x._1 <= x._2), "LowerBoundsOnCoefficients should always " +
+        .forall(x => x._1 <= x._2), "LowerBoundsOnCoefficients should always be " +
         "less than or equal to upperBoundsOnCoefficients, but found: " +
         s"lowerBoundsOnCoefficients = $getLowerBoundsOnCoefficients, " +
         s"upperBoundsOnCoefficients = $getUpperBoundsOnCoefficients.")
     }
     if (isSet(lowerBoundsOnIntercepts) && isSet(upperBoundsOnIntercepts)) {
       require($(lowerBoundsOnIntercepts).toArray.zip($(upperBoundsOnIntercepts).toArray)
-        .forall(x => x._1 <= x._2), "LowerBoundsOnIntercepts should always " +
+        .forall(x => x._1 <= x._2), "LowerBoundsOnIntercepts should always be " +
         "less than or equal to upperBoundsOnIntercepts, but found: " +
         s"lowerBoundsOnIntercepts = $getLowerBoundsOnIntercepts, " +
         s"upperBoundsOnIntercepts = $getUpperBoundsOnIntercepts.")