Monthly Archives: June 2019

Archive of posts published in the specified Month

Machine Learning Part 6 — Matrix multiplication in SQL

This is the sixth part of the ML series. For your convenience you can find other parts in the table of contents in Part 1 – Linear regression in MXNet Today we are going to implement a matrix multiplication in Redshift. Let’s go.…

Spark and NegativeArraySizeException

Recently I was debugging the following crash in Spark:

Disabling Kryo solves the issue. To do that just set spark.serializer to org.apache.spark.serializer.JavaSerializer. Other workaround is to change Kryo’s reference management, as explained on Github:

Spark and NullPointerException in UTF8String.contains

Recently I was debugging a NullPointerException in Spark. The stacktrace was indicating this:

After some digging I found out that the following query causes the problem:

If I commented out the line with the comment the NPE was no longer there.…

Playing With args4j Part 5 — Safe setters

This is the fifth part of the Playing With args4j series. For your convenience you can find other parts in the table of contents in Part 1 – Mixins There is one more problem with our setters — they are not type safe.…

Playing With args4j Part 4 — Nicer setters

This is the fourth part of the Playing With args4j series. For your convenience you can find other parts in the table of contents in Part 1 – Mixins Last time we ended with the setter of a form

. What we don’t…