[SPARK-18812][MLLIB] explain "Spark ML"

## What changes were proposed in this pull request?

There has been some confusion around "Spark ML" vs. "MLlib". This PR adds some FAQ-like entries to the MLlib user guide to explain "Spark ML" and reduce the confusion.

I check the [Spark FAQ page](http://spark.apache.org/faq.html), which seems too high-level for the content here. So I added it to the MLlib user guide instead.

cc: mateiz

Author: Xiangrui Meng <meng@databricks.com>

Closes #16241 from mengxr/SPARK-18812.
This commit is contained in:
Xiangrui Meng 2016-12-09 17:34:52 -08:00
parent cf33a86285
commit d2493a203e

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@ -35,6 +35,18 @@ The primary Machine Learning API for Spark is now the [DataFrame](sql-programmin
* The DataFrame-based API for MLlib provides a uniform API across ML algorithms and across multiple languages.
* DataFrames facilitate practical ML Pipelines, particularly feature transformations. See the [Pipelines guide](ml-pipeline.html) for details.
*What is "Spark ML"?*
* "Spark ML" is not an official name but occasionally used to refer to the MLlib DataFrame-based API.
This is majorly due to the `org.apache.spark.ml` Scala package name used by the DataFrame-based API,
and the "Spark ML Pipelines" term we used initially to emphasize the pipeline concept.
*Is MLlib deprecated?*
* No. MLlib includes both the RDD-based API and the DataFrame-based API.
The RDD-based API is now in maintenance mode.
But neither API is deprecated, nor MLlib as a whole.
# Dependencies
MLlib uses the linear algebra package [Breeze](http://www.scalanlp.org/), which depends on