Different events can cause the JVM to pause all the application threads. Such pauses are called Stop-The-World (STW) pauses. The most common cause for an STW pause to be triggered is garbage collection (example in github) , but different JIT actions (example), biased lock revocation (example), certain JVMTI operations , and many more also require the application to be stopped.
Tag Archives: JIT
This got me thinking about the different ways in Java to concatenate Strings and how they would all perform against each other. These are the methods I’m going to investigate:
- Using the + operator
- Using a StringBuilder
- Using a StringBuffer
- Using String.concat()
- Using String.join (new in Java8)
- Concatenating two Strings together as a single call, for example in a logging message. Because this is only one call you would have thought that performance is hardly an issue but the results are still interesting and shed light on the subject.
- Concatenating two Strings in a loop. Here performance is much more of an issue especially if your loops are large.
My initial thoughts and questions were as follows:
- The + operator is implemented with StringBuilder, so at least in the case of concatenating two Strings it should produce similar results to StringBuilder. What exactly is going on under the covers?
- StringBuilder should be the most efficient method, after all the class was designed for the very purpose of concatenating Strings and supersedes StringBuffer. But what is the overhead of creating the StringBuilder when compared with String.concat()?
- StringBuffer was the original class for concatenating Strings – unfortunately its methods are synchronized. There really is no need for the synchronization and it was subsequently replaced by StringBuilder which is not synchronized. The question is, does the JIT optimise away the synchronisation?
- String.concat() ought to work well for 2 strings but does it work well in a loop?
- String.join() has more functionality that StringBuilder, how does it affect performance if we instruct it to join Strings using an empty delimiter?
HOPE is a specialized method-at-a-time JIT compiler written in Python for translating Python source code into C++ and compiles this at runtime. In contrast to other existing JIT compliers, which are designed for general purpose, we have focused our development of the subset of the Python language that is most relevant for astrophysical calculations. By concentrating on this subset, HOPE is able to achieve the highest possible performance
By using HOPE, the user can benefit from being able to write common numerical code in Python and having the performance of compiled implementation. To enable the HOPE JIT compilation, the user needs to add a decorator to the function definition. The package does not require additional information, which ensures that HOPE is as non-intrusive as possible: