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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. First, let’s see what we want to calculate: Nothing fancy. … Continue reading Machine Learning Part 6 — Matrix multiplication in SQL
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:
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. Also, when I replaced either df2(“ref”) or df1(“ref”) with lit(“ref”) it was not crashing … Continue reading Spark and NullPointerException in UTF8String.contains
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. This means that we may have integer parameter: And then we can … Continue reading Playing With args4j Part 5 — Safe 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 like here is the last parameters — why would we want to … Continue reading Playing With args4j Part 4 — Nicer setters