Came up with some confusion regarding the information on SparkUI. The
following info is gathered while factorizing a large matrix using ALS:
1. some stages have more succeeded tasks than total tasks, which are
displayed in the 5th column.
2. duplicate stages with exactly same stageID (stage 1/3/7)
3. Clicking into some stages, some executors cannot be addressed. Does
that mean lost of executor or this does not matter?