The goal of this experiment was to add the support for the Graal JIT to jython, a Python interpreter running on the JVM. The implementation was made following this guide.
After making the decision to use Jython for this experiment, the first thing I did was to rewrite the Mandelbrot benchmark in Python, staying as close to the original as possible.
I then ran the benchmarks and got the following results:
- The Python benchmark is around 2 times faster with Jython than with the regular Python2.7 interpreter
- The native Java benchmark is more than 20 times faster than the Python benchmark with Jython
I was expecting faster results with the native Java code, but definitely not by a factor of 20...
My Python code could be an issue (since I wanted to keep it as simple as possible), but even then I thought that there was room for improvements and went on with the implementation.
The Truffle framework is used if Jython is started with a file and with the argument --truffle.
After that, the class ASTVisitor (that wound up not being an actual Visitor) makes a translation of the Jython AST using the Truffle framework.
The new AST is then executed by the Graal VM.
The implementation part was very straightforward, and I only had a few serious issues:
- First of all, there was no way to differenciate between an access to a function parameter or a local variable with the Jython AST, so I had to manually add the parameters to the frame during a function call and treat them as local variables
- Also, as I didn't want to compile the whole
timemodule to run the benchmark, I created a special node to manage calls totime.time()
My first implementation could only use objects, and adding the support for primitive types reduced the execution time by a factor of 4 (which corresponds to the results obtained by the author of the guide).
Here are the results obtained by running the Mandelbrot benchmark 100 times for each interpreter, and keeping the 10 last results:
| Interpreter | Time (µs) |
|---|---|
| Java | 110 311 ± 3 527 |
| Jython + Graal | 148 214 ± 1 334 |
| Jython | 2 814 300 ± 539 700 |
| Python2.7 | 5 528 607 ± 300 144 |
In the end, the results are very close to native Java, and the execution time was actually divided by nearly 20, which seemed impossible at first.