A quick hack to wrap Google Guava's cache with a slightly more scala-friendly API. The main goal is to have a getOrElseUpdate method that is actually thread safe, unlike the one on Scala's ConcurrentMap.

beräkna punktprodukten (skalär produkt) för två glesa vektorer i Scala. Map val Sparse1 = Map[Int, Int]() for (k <- 0 to 20) { Sparse1 getOrElseUpdate (k, 

But it turns out that Scala collections already provide the getOrElseUpdate method on mutable maps. The 8 lines above translate simply into: 1 2. def getModelState(modelPrefixedId: String) = modelStates. The getOrElseUpdate is useful for accessing maps that act as caches. Say you have an expensive computation triggered by invoking a function f : scala> def f(x: String) = { println("taking my time."); sleep(100) x.reverse } f: (x: String)String The getOrElseUpdate is useful for accessing maps that act as caches. Say you have an expensive computation triggered by invoking a function f : scala> def f(x: String) = { println("taking my time."); sleep(100) x.reverse } f: (x: String)String Since we supported 2.10 we included our own simple atomic implementation.

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Som titel import scala.collection.mutable val map = mutable. getOrElseUpdate(100, (0, 0)) res3: (Int, Int) = (0,0) scala> googleMap res4:  Jag är helt ny på att programmera med Scala och jag har följande problem: Jag getOrElseUpdate(key, new ListBuffer()) get('Strings') += 'a' get('Strings') += 'b'  beräkna punktprodukten (skalär produkt) för två glesa vektorer i Scala. Map val Sparse1 = Map[Int, Int]() for (k <- 0 to 20) { Sparse1 getOrElseUpdate (k,  Can the highlighted with comment line be rewritten using the getOrElseUpdate method? P.S. I am only at the 4th part of the "Scala for the impatient", so please don't teach me now about functional Scala which, I am sure, can be more beautiful here. Thanks. This is typically logic you would write in Java, and it looks great in some ways: it uses pattern matching, the tuple arrow (->), etc.But it turns out that Scala collections already provide the getOrElseUpdate method on mutable maps. Scala’s Predef object offers an implicit conversion that lets you write key -> value as an alternate syntax ms getOrElseUpdate (k, d) If key k is defined in map But the method getOrElseUpdate of scala.co The ScalaDoc states that a scala.collection.concurrent.TrieMap is thread-safe: A concurrent hash-trie or TrieMap is a concurrent thread-safe lock-free implementation of a hash array mapped trie.

The getOrElseUpdate is useful for accessing maps that act as caches. Say you have an expensive computation triggered by invoking a function f : scala> def f(x: String) = { println("taking my time."); sleep(100) x.reverse } f: (x: String)String

The factory creates 'Some(x)' if the argument is not null, and 'None' if it is null. The 'getOrElse(Default)' method goes into the Scala class hierarchy… Return optional values from a function with the Option class.

Spark version : 2 Steps:. install conda on all nodes (python2.7) ( pip install conda ) create requirement1.txt with "numpy > requirement1.txt "Run kmeans.py application in yarn-client mode.

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HashMap defines getOrElseUpdate, += HashMap API. scala> val numbers = collection.mutable.Map(1 -> 2) numbers: scala.collection.mutable.Map[Int,Int] = Map((1,2)) scala> numbers.get(1) res0: Option[Int] = Some(2) scala> numbers.getOrElseUpdate(2, 3) res54: Int = 3 scala> numbers res55: scala.collection.mutable.Map[Int,Int] = Map((2,3), (1,2)) scala> numbers += (4 -> 1) res56: numbers.type = Map((2,3), (4,1), (1,2)) 2011-05-29 · Scala is amazing! It allows us to pass a function to getOrElseUpdate in case the value hasn’t already been evaluated. So f(x) is only evaluated iff the key x is not available. Note we call this a Memoize1 class since it extends Function1, i.e., a function that takes 1 argument. In this tutorial, we’ll learn how to use Play’s caching API with Scala. This API, while surprisingly simple, addresses many of the situations where we’d like to cache results rather than re-fetching them from a slower system.
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Oct 9, 2019 ```scala private def consumeAbortedTxnsUpTo(offset: Long): Unit = { while ( abortedTransactions. getOrElseUpdate(abortedTxn.producerId  Nov 27, 2020 [source, scala]¶. compute( split: Partition, context: TaskContext): Iterator[T].

.getOrElseUpdate makes it convenient to use a mutable Map as a cache: the second parameter to .getOrElseUpdate is a lazy "by-name" parameter, and is only evaluated when the key is not found in the Map. This provides the common "check if key present, if so return value, otherwise insert new value and return that" workflow built in. As discussed above, the getOrElseUpdate () method retrieves the specified tweets from the cache if they exist, otherwise, it calls our wrapper for the Twitter API to retrieve the latest values. This is a very common usage pattern for any cache.
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17/01/10 19:17:20 ERROR ShuffleBlockFetcherIterator: Failed to get block(s) from bigdata-hdp-apache1828.xg01.diditaxi.com:7337 java.lang.NullPointerException: group

Extract the getOrElseUpdate into another interface that concurrent maps do not inherit, but non-thread-safe maps like mutable.HashMap do. Have ParTrieMap throw an exception for getOrElseUpdate.

OS: Ubuntu Linux 18.10. Java: java version "1.8.0_201" Java(TM) SE Runtime Environment (build 1.8.0_201-b09) Java HotSpot(TM) 64-Bit Server VM (build 25.201-b09, mixed mode)

Remove these request types or add at least one field to the request type. Play Framework - The High Velocity Web Framework For Java and Scala. Note : getOrElseUpdate is not an atomic operation in EhCache and is implemented  Scala parallel collections allow you to solve data parallelism problems in ms getOrElseUpdate(k, d), If key k is defined in map ms, return its associated value. scala> Map('a' -> 1, 'b' -> 2) res4: scala.collection.immutable.Map[Char getOrElseUpdate(2, 3) res54: Int = 3 scala> numbers res55: scala.collection.

You can vote up the ones you like or vote down the ones you don't like, and go to the original project or source file by following the links above each example. A quick hack to wrap Google Guava's cache with a slightly more scala-friendly API. The main goal is to have a getOrElseUpdate method that is actually thread safe, unlike the one on Scala's ConcurrentMap. [Redirected to scala-language since I'm not on scala-user.] Someone asked me recently why I'm against extending Function1 casually. In this we have a pretty good example. I'm not sure why you declared the map to be an implicit val: implicit val cache = mutable.Map[Int, String]() I imagine you didn't do that with the intention of placing a competing A good anecdotal example from the Scala community for this is the latest pattern matcher in the Scala compiler - although the previous one was more efficient, and knew how to optimize overlapping match cases better, the new pattern matcher rewrite is simpler to understand, less buggy and easier to maintain.