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Gravel

Gravel is a Smalltalk implementation for the JVM. For more information ask around in the gravel-st google group or see the wiki.

Getting started

Gravel Smalltalk requires maven and an (Oracle|OpenJDK) Java 7 installation. Generate an eclipse project with the usual

mvn eclipse:eclipse

To open the IDE; load everything in eclipse and start st.gravel.tools.StartJetty. Then point your browser to http://localhost:8080/browser

What is Gravel

Gravel is a modern Smalltalk implementation for the JVM. It's aim is to provide an interactive development environment in the Smalltalk philosophy as well as a stable and fast runtime platform. Gravel aims to be fully ANSI Smalltalk compatible.

Implementation

The parser and patching-compiler of Gravel is written in Smalltalk with Type annotations. These type annotations allow these parts of gravel to be transformed to Java source code. The runtime system then uses this compiler to generate bytecode. It uses the JSR-292 invokedynamic facilities.

Features

  • Traits
  • Optional typing
  • Patching compiler
  • Full block closures
  • Resumable exceptions
  • Namespaces
  • Mirror based reflection facilities

Common Smalltalk features that we probably won't support

  • become:
  • thisContext

Benchmarks

Some preliminary benchmark results of running DeltaBlue>>longBenchmark for five iterations on my Intel(R) Xeon(R) CPU E31270 @ 3.40GHz. The good stuff:

Reference Java Implementation :

Duration: 2030 ms
Duration: 2012 ms
Duration: 1996 ms
Duration: 2042 ms
Duration: 2057 ms

Reference Smalltalk Implementation in Gravel:

Duration: 3651 ms
Duration: 1420 ms
Duration: 1311 ms
Duration: 1376 ms
Duration: 1304 ms

As we can see after the first iteration the hotspot compiler kicks.

The bad: Gravel isn't at its best with the Richards benchmark. To compare Java with Gravel:

Java:

Duration: 28 ms
Duration: 8 ms
Duration: 8 ms
Duration: 7 ms
Duration: 7 ms

Gravel:

100 iterations run in: 1937 ms
100 iterations run in: 1280 ms
100 iterations run in: 1272 ms
100 iterations run in: 1295 ms
100 iterations run in: 1278 ms