This patch adds an API entry point for single decision tree feature importances.

Author: sethah <seth.hendrickson16@gmail.com>

Closes #9912 from sethah/SPARK-11861.

## What changes were proposed in this pull request?
```GeneralizedLinearRegression``` supports ```save/load```.
cc mengxr
## How was this patch tested?
unit test.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #11465 from yanboliang/spark-13615.

## What changes were proposed in this pull request?

In order to make `docs/examples` (and other related code) more simple/readable/user-friendly, this PR replaces existing codes like the followings by using `diamond` operator.

```
-    final ArrayList<Product2<Object, Object>> dataToWrite =
-      new ArrayList<Product2<Object, Object>>();
+    final ArrayList<Product2<Object, Object>> dataToWrite = new ArrayList<>();
```

Java 7 or higher supports **diamond** operator which replaces the type arguments required to invoke the constructor of a generic class with an empty set of type parameters (<>). Currently, Spark Java code use mixed usage of this.

## How was this patch tested?

Manual.
Pass the existing tests.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #11541 from dongjoon-hyun/SPARK-13702.

## What changes were proposed in this pull request?
Although we defined ```checkModelData``` in [```read/write``` test](https://github.com/apache/spark/blob/master/mllib/src/test/scala/org/apache/spark/ml/regression/LinearRegressionSuite.scala#L994) of ML estimators/models and pass it to ```testEstimatorAndModelReadWrite```, ```testEstimatorAndModelReadWrite``` omits to call ```checkModelData``` to check the equality of model data. So actually we did not run the check of model data equality for all test cases currently, we should fix it.
BTW, fix the bug of LDA read/write test which did not set ```docConcentration```. This bug should have failed test, but it does not complain because we did not run ```checkModelData``` actually.
cc jkbradley mengxr
## How was this patch tested?
No new unit test, should pass the exist ones.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #11513 from yanboliang/ml-check-model-data.

## What changes were proposed in this pull request?

Remove last usage of jblas, in tests

## How was this patch tested?

Jenkins tests -- the same ones that are being modified.

Author: Sean Owen <sowen@cloudera.com>

Closes #11560 from srowen/SPARK-13715.

`HadoopFsRelation` is used for reading most files into Spark SQL.  However today this class mixes the concerns of file management, schema reconciliation, scan building, bucketing, partitioning, and writing data.  As a result, many data sources are forced to reimplement the same functionality and the various layers have accumulated a fair bit of inefficiency.  This PR is a first cut at separating this into several components / interfaces that are each described below.  Additionally, all implementations inside of Spark (parquet, csv, json, text, orc, svmlib) have been ported to the new API `FileFormat`.  External libraries, such as spark-avro will also need to be ported to work with Spark 2.0.

### HadoopFsRelation
A simple `case class` that acts as a container for all of the metadata required to read from a datasource.  All discovery, resolution and merging logic for schemas and partitions has been removed.  This an internal representation that no longer needs to be exposed to developers.

```scala
case class HadoopFsRelation(
    sqlContext: SQLContext,
    location: FileCatalog,
    partitionSchema: StructType,
    dataSchema: StructType,
    bucketSpec: Option[BucketSpec],
    fileFormat: FileFormat,
    options: Map[String, String]) extends BaseRelation
```

### FileFormat
The primary interface that will be implemented by each different format including external libraries.  Implementors are responsible for reading a given format and converting it into `InternalRow` as well as writing out an `InternalRow`.  A format can optionally return a schema that is inferred from a set of files.

```scala
trait FileFormat {
  def inferSchema(
      sqlContext: SQLContext,
      options: Map[String, String],
      files: Seq[FileStatus]): Option[StructType]

  def prepareWrite(
      sqlContext: SQLContext,
      job: Job,
      options: Map[String, String],
      dataSchema: StructType): OutputWriterFactory

  def buildInternalScan(
      sqlContext: SQLContext,
      dataSchema: StructType,
      requiredColumns: Array[String],
      filters: Array[Filter],
      bucketSet: Option[BitSet],
      inputFiles: Array[FileStatus],
      broadcastedConf: Broadcast[SerializableConfiguration],
      options: Map[String, String]): RDD[InternalRow]
}
```

The current interface is based on what was required to get all the tests passing again, but still mixes a couple of concerns (i.e. `bucketSet` is passed down to the scan instead of being resolved by the planner).  Additionally, scans are still returning `RDD`s instead of iterators for single files.  In a future PR, bucketing should be removed from this interface and the scan should be isolated to a single file.

### FileCatalog
This interface is used to list the files that make up a given relation, as well as handle directory based partitioning.

```scala
trait FileCatalog {
  def paths: Seq[Path]
  def partitionSpec(schema: Option[StructType]): PartitionSpec
  def allFiles(): Seq[FileStatus]
  def getStatus(path: Path): Array[FileStatus]
  def refresh(): Unit
}
```

Currently there are two implementations:
 - `HDFSFileCatalog` - based on code from the old `HadoopFsRelation`.  Infers partitioning by recursive listing and caches this data for performance
 - `HiveFileCatalog` - based on the above, but it uses the partition spec from the Hive Metastore.

### ResolvedDataSource
Produces a logical plan given the following description of a Data Source (which can come from DataFrameReader or a metastore):
 - `paths: Seq[String] = Nil`
 - `userSpecifiedSchema: Option[StructType] = None`
 - `partitionColumns: Array[String] = Array.empty`
 - `bucketSpec: Option[BucketSpec] = None`
 - `provider: String`
 - `options: Map[String, String]`

This class is responsible for deciding which of the Data Source APIs a given provider is using (including the non-file based ones).  All reconciliation of partitions, buckets, schema from metastores or inference is done here.

### DataSourceAnalysis / DataSourceStrategy
Responsible for analyzing and planning reading/writing of data using any of the Data Source APIs, including:
 - pruning the files from partitions that will be read based on filters.
 - appending partition columns*
 - applying additional filters when a data source can not evaluate them internally.
 - constructing an RDD that is bucketed correctly when required*
 - sanity checking schema match-up and other analysis when writing.

*In the future we should do that following:
 - Break out file handling into its own Strategy as its sufficiently complex / isolated.
 - Push the appending of partition columns down in to `FileFormat` to avoid an extra copy / unvectorization.
 - Use a custom RDD for scans instead of `SQLNewNewHadoopRDD2`

Author: Michael Armbrust <michael@databricks.com>
Author: Wenchen Fan <wenchen@databricks.com>

Closes #11509 from marmbrus/fileDataSource.

Add save/load for feature.py. Meanwhile, add save/load for `ElementwiseProduct` in Scala side and fix a bug of missing `setDefault` in `VectorSlicer` and `StopWordsRemover`.

In this PR I ignore the `RFormula` and `RFormulaModel` because its Scala implementation is pending in https://github.com/apache/spark/pull/9884. I'll add them in this PR if https://github.com/apache/spark/pull/9884 gets merged first. Or add a follow-up JIRA for `RFormula`.

Author: Xusen Yin <yinxusen@gmail.com>

Closes #11203 from yinxusen/SPARK-13036.

## What changes were proposed in this pull request?

It avoids counting the dataframe twice.

Author: Abou Haydar Elias <abouhaydar.elias@gmail.com>
Author: Elie A <abouhaydar.elias@gmail.com>

Closes #11491 from eliasah/quantile-discretizer-patch.

## What changes were proposed in this pull request?

This PR fixes typos in comments and testcase name of code.

## How was this patch tested?

manual.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #11481 from dongjoon-hyun/minor_fix_typos_in_code.

## What changes were proposed in this pull request?
Remove duplicated periods at the end of some sharedParams in ScalaDoc, such as [here](https://github.com/apache/spark/pull/11344/files#diff-9edc669edcf2c0c7cf1efe4a0a57da80L367)
cc mengxr srowen
## How was this patch tested?
Documents change, no test.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #11344 from yanboliang/shared-cleanup.

## What changes were proposed in this pull request?

After SPARK-6990, `dev/lint-java` keeps Java code healthy and helps PR review by saving much time.
This issue aims remove unused imports from Java/Scala code and add `UnusedImports` checkstyle rule to help developers.

## How was this patch tested?
```
./dev/lint-java
./build/sbt compile
```

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #11438 from dongjoon-hyun/SPARK-13583.

## What changes were proposed in this pull request?

Make some cross-cutting code improvements according to static analysis. These are individually up for discussion since they exist in separate commits that can be reverted. The changes are broadly:

- Inner class should be static
- Mismatched hashCode/equals
- Overflow in compareTo
- Unchecked warnings
- Misuse of assert, vs junit.assert
- get(a) + getOrElse(b) -> getOrElse(a,b)
- Array/String .size -> .length (occasionally, -> .isEmpty / .nonEmpty) to avoid implicit conversions
- Dead code
- tailrec
- exists(_ == ) -> contains find + nonEmpty -> exists filter + size -> count
- reduce(_+_) -> sum map + flatten -> map

The most controversial may be .size -> .length simply because of its size. It is intended to avoid implicits that might be expensive in some places.

## How was the this patch tested?

Existing Jenkins unit tests.

Author: Sean Owen <sowen@cloudera.com>

Closes #11292 from srowen/SPARK-13423.

Estimator for Generalized Linear Models(GLMs) which will be solved by IRLS.

cc mengxr

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #11136 from yanboliang/spark-12811.

JIRA: https://issues.apache.org/jira/browse/SPARK-13506

## What changes were proposed in this pull request?

just chang R Snippet Comment in  AssociationRulesSuite

## How was this patch tested?

unit test passsed

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #11387 from zhengruifeng/ars.

[SPARK-13545][MLLIB][PYSPARK] Make MLlib LogisticRegressionWithLBFGS's default parameters consistent in Scala and Python

## What changes were proposed in this pull request?
* The default value of ```regParam``` of PySpark MLlib ```LogisticRegressionWithLBFGS``` should be consistent with Scala which is ```0.0```. (This is also consistent with ML ```LogisticRegression```.)
* BTW, if we use a known updater(L1 or L2) for binary classification, ```LogisticRegressionWithLBFGS``` will call the ML implementation. We should update the API doc to clarifying ```numCorrections``` will have no effect if we fall into that route.
* Make a pass for all parameters of ```LogisticRegressionWithLBFGS```, others are set properly.

cc mengxr dbtsai
## How was this patch tested?
No new tests, it should pass all current tests.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #11424 from yanboliang/spark-13545.

Part of task for [SPARK-11219](https://issues.apache.org/jira/browse/SPARK-11219) to make PySpark MLlib parameter description formatting consistent.  This is for the tree module.

closes #10601

Author: Bryan Cutler <cutlerb@gmail.com>
Author: vijaykiran <mail@vijaykiran.com>

Closes #11353 from BryanCutler/param-desc-consistent-tree-SPARK-12634.

## What changes were proposed in this pull request?

This is another try of PR #11323.

This PR removes DataFrame RDD operations except for `foreach` and `foreachPartitions` (they are actions rather than transformations). Original calls are now replaced by calls to methods of `DataFrame.rdd`.

PR #11323 was reverted because it introduced a regression: both `DataFrame.foreach` and `DataFrame.foreachPartitions` wrap underlying RDD operations with `withNewExecutionId` to track Spark jobs. But they are removed in #11323.

## How was the this patch tested?

No extra tests are added. Existing tests should do the work.

Author: Cheng Lian <lian@databricks.com>

Closes #11388 from liancheng/remove-df-rdd-ops.

jira: https://issues.apache.org/jira/browse/SPARK-13028
MaxAbsScaler works in a very similar way as MinMaxScaler, but scales in a way that the training data lies within the range [-1, 1] by dividing through the largest maximum value in each feature. The motivation to use this scaling includes robustness to very small standard deviations of features and preserving zero entries in sparse data.

Unlike StandardScaler and MinMaxScaler, MaxAbsScaler does not shift/center the data, and thus does not destroy any sparsity.

Something similar from sklearn:
http://scikit-learn.org/stable/modules/generated/sklearn.preprocessing.MaxAbsScaler.html#sklearn.preprocessing.MaxAbsScaler

Author: Yuhao Yang <hhbyyh@gmail.com>

Closes #10939 from hhbyyh/maxabs and squashes the following commits:

fd8bdcd [Yuhao Yang] add tag and some optimization on fit
648fced [Yuhao Yang] Merge remote-tracking branch 'upstream/master' into maxabs
75bebc2 [Yuhao Yang] Merge remote-tracking branch 'upstream/master' into maxabs
cb10bb6 [Yuhao Yang] remove minmax
91ef8f3 [Yuhao Yang] ut added
8ab0747 [Yuhao Yang] Merge remote-tracking branch 'upstream/master' into maxabs
a9215b5 [Yuhao Yang] max abs scaler

## What changes were proposed in this pull request?
ML StringIndexer does not protect itself from column name duplication.

We should still improve a way to validate a schema of `StringIndexer` and `StringIndexerModel`.  However, it would be great to fix at another issue.

## How was this patch tested?
unit test

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #11370 from yu-iskw/SPARK-12874.

This reverts commit 157fe64f.

## What changes were proposed in this pull request?

This PR removes DataFrame RDD operations. Original calls are now replaced by calls to methods of `DataFrame.rdd`.

## How was the this patch tested?

No extra tests are added. Existing tests should do the work.

Author: Cheng Lian <lian@databricks.com>

Closes #11323 from liancheng/remove-df-rdd-ops.

## What changes were proposed in this pull request?
Like #11027 for ```LogisticRegression```, ```LinearRegression``` with L1 regularization should also cache the value of the ```standardization``` rather than re-fetching it from the ```ParamMap``` for every OWLQN iteration.
cc srowen

## How was this patch tested?
No extra tests are added. It should pass all existing tests.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #11367 from yanboliang/spark-13490.

## What changes were proposed in this pull request?

Change line 113 of QuantileDiscretizer.scala to

`val requiredSamples = math.max(numBins * numBins, 10000.0)`

so that `requiredSamples` is a `Double`.  This will fix the division in line 114 which currently results in zero if `requiredSamples < dataset.count`

## How was the this patch tested?
Manual tests.  I was having a problems using QuantileDiscretizer with my a dataset and after making this change QuantileDiscretizer behaves as expected.

Author: Oliver Pierson <ocp@gatech.edu>
Author: Oliver Pierson <opierson@umd.edu>

Closes #11319 from oliverpierson/SPARK-13444.

https://issues.apache.org/jira/browse/SPARK-13011

Author: Xusen Yin <yinxusen@gmail.com>

Closes #11124 from yinxusen/SPARK-13011.

Author: Grzegorz Chilkiewicz <grzegorz.chilkiewicz@codilime.com>

Closes #11216 from grzegorz-chilkiewicz/master.

`GraphImpl.fromExistingRDDs` expects preprocessed vertex RDD as input. We call it in LDA without validating this requirement. So it might introduce errors. Replacing it by `Graph.apply` would be safer and more proper because it is a public API. The tests still pass. So maybe it is safe to use `fromExistingRDDs` here (though it doesn't seem so based on the implementation) or the test cases are special. jkbradley ankurdave

Author: Xiangrui Meng <meng@databricks.com>

Closes #11226 from mengxr/SPARK-13355.

## What changes were proposed in this pull request?
In order to provide better and consistent result, let's change the default value of MLlib ```LogisticRegressionWithLBFGS convergenceTol``` from ```1E-4``` to ```1E-6``` which will be equal to ML ```LogisticRegression```.
cc dbtsai
## How was the this patch tested?
unit tests

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #11299 from yanboliang/spark-13429.

[SPARK-13295][ ML, MLLIB ] AFTSurvivalRegression.AFTAggregator improvements - avoid creating new instances of arrays/vectors for each record

As also mentioned/marked by TODO in AFTAggregator.AFTAggregator.add(data: AFTPoint) method a new array is being created for intercept value and it is being concatenated
with another array which contains the betas, the resulted Array is being converted into a Dense vector which in its turn is being converted into breeze vector.
This is expensive and not necessarily beautiful.

I've tried to solve above mentioned problem by simple algebraic decompositions - keeping and treating intercept independently.

Please let me know what do you think and if you have any questions.

Thanks,
Narine

Author: Narine Kokhlikyan <narine.kokhlikyan@gmail.com>

Closes #11179 from NarineK/survivaloptim.

ML ```KMeansModel / BisectingKMeansModel / QuantileDiscretizer``` should set parent.

cc mengxr

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #11214 from yanboliang/spark-13334.

Part of task for [SPARK-11219](https://issues.apache.org/jira/browse/SPARK-11219) to make PySpark MLlib parameter description formatting consistent.  This is for the fpm and recommendation modules.

Closes #10602
Closes #10897

Author: Bryan Cutler <cutlerb@gmail.com>
Author: somideshmukh <somilde@us.ibm.com>

Closes #11186 from BryanCutler/param-desc-consistent-fpmrecc-SPARK-12632.

## What changes were proposed in this pull request?

This PR tries to fix all typos in all markdown files under `docs` module,
and fixes similar typos in other comments, too.

## How was the this patch tested?

manual tests.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #11300 from dongjoon-hyun/minor_fix_typos.

[SPARK-12153][SPARK-7617][MLLIB] add support of arbitrary length sentence and other tuning for Word2Vec

add support of arbitrary length sentence by using the nature representation of sentences in the input.

add new similarity functions and add normalization option for distances in synonym finding
add new accessor for internal structure(the vocabulary and wordindex) for convenience

need instructions about how to set value for the Since annotation for newly added public functions. 1.5.3?

jira link: https://issues.apache.org/jira/browse/SPARK-12153

Author: Yong Gang Cao <ygcao@amazon.com>
Author: Yong-Gang Cao <ygcao@users.noreply.github.com>

Closes #10152 from ygcao/improvementForSentenceBoundary.

## What changes were proposed in this pull request?
Fix MLlib LogisticRegressionWithLBFGS regularization map as:
```SquaredL2Updater``` -> ```elasticNetParam = 0.0```
```L1Updater``` -> ```elasticNetParam = 1.0```
cc dbtsai
## How was the this patch tested?
unit tests

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #11258 from yanboliang/spark-13379.

This PR fixes some warnings found by `build/sbt mllib/test:compile`.

Author: Xiangrui Meng <meng@databricks.com>

Closes #11227 from mengxr/fix-mllib-warnings-201602.

This documents the implementation of ALS in `spark.ml` with example code in scala, java and python.

Author: BenFradet <benjamin.fradet@gmail.com>

Closes #10411 from BenFradet/SPARK-12247.

This enhancement extends the existing SparkML Binarizer [SPARK-5891] to allow Vector in addition to the existing Double input column type.

A use case for this enhancement is for when a user wants to Binarize many similar feature columns at once using the same threshold value (for example a binary threshold applied to many pixels in an image).

This contribution is my original work and I license the work to the project under the project's open source license.

viirya mengxr

Author: seddonm1 <seddonm1@gmail.com>

Closes #10976 from seddonm1/master.

JIRA: https://issues.apache.org/jira/browse/SPARK-12363

This issue is pointed by yanboliang. When `setRuns` is removed from PowerIterationClustering, one of the tests will be failed. I found that some `dstAttr`s of the normalized graph are not correct values but 0.0. By setting `TripletFields.All` in `mapTriplets` it can work.

Author: Liang-Chi Hsieh <viirya@gmail.com>
Author: Xiangrui Meng <meng@databricks.com>

Closes #10539 from viirya/fix-poweriter.

https://issues.apache.org/jira/browse/SPARK-12746

Author: Earthson Lu <Earthson.Lu@gmail.com>

Closes #10697 from Earthson/SPARK-12746.

https://issues.apache.org/jira/browse/SPARK-12765

Author: Liu Xiang <lxmtlab@gmail.com>

Closes #10720 from sloth2012/sloth.

cc jkbradley

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #9535 from yu-iskw/SPARK-11515.