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Evan Chan velvia

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View gist:8921238

Useful Scalac Flags

So, there have been some discussions and angry tweets recently about irritating Scala "features" (like value discarding and auto-tupling) that can actually be turned off by selecting the right compiler flag in conjunction with -Xfatal-warnings. I highly recommend a set of options something like those below.

scalacOptions ++= Seq(
  "-encoding", "UTF-8",       // yes, this is 2 args
velvia / gist:8967611
Last active Aug 29, 2015
Chunking Array Serializer/Deserializer in Scala
View gist:8967611
// We want a generic way to chunk large arrays into segments of byte arrays
// and to do so in a way that doesn't blow up memory for large objects, ie ability to chunk / page / stream
trait ChunkingArraySerDe[T] {
def apply(data: Array[T], chunkSize: Int): Iterator[Array[Byte]]
def unapply(serialized: Iterator[Array[Byte]]): Array[T]
// For arrays with fixed-size elements
trait PrimitiveChunkingSerDe[@specialized(Int, Long, Boolean) T] extends ChunkingArraySerDe[T] {
velvia / gist:10447394
Created Apr 11, 2014
Patch to spark-jobserver to clean up GC
View gist:10447394
case StopContext(name) =>
if (contexts contains name) {"Shutting down context {}", name) // watch for termination event
contexts(name) ! PoisonPill
sender ! ContextStopped
} else {
sender ! NoSuchContext
velvia / gist:909408dc6f053d6934be
Created Jun 29, 2015
Patch to Phantom 1.8.x for ByteBuffer handling
View gist:909408dc6f053d6934be
// Primitive.scala - only change is asCql method
implicit object BlobIsPrimitive extends Primitive[ByteBuffer] {
override type PrimitiveType = java.nio.ByteBuffer
val cassandraType = CQLSyntax.Types.Blob
override def fromRow(column: String, row: Row): Try[ByteBuffer] = nullCheck(column, row) {
r => r.getBytes(column)
velvia / gist:213b837c6e02c4982a9a
Last active Sep 21, 2015
Notes for velvia/filo 50x performance improvement
View gist:213b837c6e02c4982a9a be turned into a blog post later. These are notes with references to commits, the blog post will have snippets of code so folks don't have to look things up.

How I tuned Filo for 50x speedup in 24 hours

Filo is an extreme serialization library for vector data. Think of it as the good parts of Parquet without the HDFS and file format garbage -- just the serdes and fast columnar storage.

I recently added a JMH benchmark for reading a Filo binary buffer containing 10,000 Ints using the simplest apply() method to sum up all the Ints.

Oh, and before we get started - avoid throwing exceptions in inner loops, especially Try(....).getOrElse(...) patterns. Even if they occur only occasionally they can be extremely expensive.

velvia /
Created Sep 30, 2015
Calling a function by type parameter in Scala

Let's say you have a Scala function which takes type parameter:

  def myFunc[K]: T

Let's say I have several functions like that. Right now, if K could be one of several different values, I'd need some code like the following:

  kType match {
velvia / gist:69ca1ab5e758d3b0ab13
Created Mar 2, 2015
JTS custom CoordinateSequence example
View gist:69ca1ab5e758d3b0ab13
import com.vividsolutions.jts.geom._
import com.vividsolutions.jts.geom.impl.PackedCoordinateSequence
import com.vividsolutions.jts.geom.util.GeometryTransformer
* A custom CoordSequence based on byte arrays for compactness and speed
* Just 2 dimensions for now.
* It's an example of creating a custom CoordinateSequence.
* NOTE: This is much more memory efficient, but slower because of deserialization cost.
velvia / spark-jobserver-ui-thoughts
Created Jul 29, 2016
Thoughts on requirements for SJS UI
View spark-jobserver-ui-thoughts
* See all current contexts
* For each context see all the jobs that are running
* History of past jobs for a given context. Actually this is not technically available via API; but history of past jobs
* Be able to see configuration for each job present or past (this is available via a tiny "C" link in current UI)
* Job results
* Link to Spark UI for detailed analysis
velvia / sparkjobapi.scala
Last active Dec 13, 2016
SCarman's spark job API on top of existing API
View sparkjobapi.scala
package spark.jobserver.api
import com.typesafe.config.Config
import org.scalactic._
import spark.jobserver.api._
trait ContextProvider[C] {
val ctx: C with ContextLike = null
def context: C with ContextLike = ctx
View gist:5690cd1b44ee7f2057a81b3b6cc100fc
:: problems summary ::
[FAILED ] org.scala-sbt#main;0.13.11!main.jar: The HTTP response code for did not indicate a success. See log for more detail. (323ms)
[FAILED ] org.scala-sbt#main;0.13.11!main.jar: The HTTP response code for did not indicate a success. See log for more detail. (323ms)
==== typesafe-ivy-releases: tried
[FAILED ] org.scala-sbt#compiler-interface;0.13.11!compiler-interface.jar: The HTTP response code for did not indicate a success. See log for more detail. (308ms)
[FAILED ] org.scala-sbt#compiler-interface;0.13.11!compiler-interface.jar: The HTTP response code for https:
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