# A surprisingly fast, surprisingly simple Actor library for Java

As part of my research work on
[Syndicate](https://syndicate-lang.org), in 2020 I built this simple
Actor library in and for Java.

It's a hybrid of Erlang-style and E-style Actor models: Erlang-style
in that it includes monitors and links, and E-style in that it peers
denote targets for messages via references to individual *objects*
with an actor. Actors are thus similar to E's *vats*.

So far, I've limited myself to implementing a straightforward Actor
system, not including Dataspace or Syndicate primitives.

## Quickstart

    git clone https://git.syndicate-lang.org/syndicate-lang/syndicate-java
    ant jar

Then, if you'd like to run the simple million-actor/200-message
benchmark discussed below, run `make ziprun`.

## Surprisingly fast

It's quite interesting all by itself, though: it's *very* fast and
able to use all the cores in a machine very effectively. For example:

    $ java ... ...example2.Main 1000000 200
    2021-05-10 11:02:35.087 INFO Actor(1) Available processors: 48
    2021-05-10 11:02:38.573 INFO Actor(1) Start
    2021-05-10 11:02:44.161 INFO Actor(1) Stop after 200000000 messages; 4.8 seconds, 41999160.0 Hz

That little benchmark has one million actors, each sending 200
messages to its neighbour in a ring, on my AMD 48-core machine. The
whole workload, 200 million messages, is delivered in under 5 seconds;
or, about 40 million messages per second. I was surprised that such a
simple system was able to perform so well.

Here's that same benchmark run on a single core:

    $ taskset -c 0 java ... ...example2.Main 1000000 200
    2021-05-10 11:07:42.104 INFO Actor(1) Available processors: 1
    2021-05-10 11:07:47.826 INFO Actor(1) Start
    2021-05-10 11:08:52.078 INFO Actor(1) Stop after 200000000 messages; 63.5 seconds, 3149903.9 Hz

That's just over 3 million messages per second on a single core. Neat, huh?

## Surprisingly simple

It's also only ~730 lines of code:

```
~/src/syndicate-java$ cloc src/main/java/
      12 text files.
      12 unique files.
       0 files ignored.

github.com/AlDanial/cloc v 1.86  T=0.01 s (965.7 files/s, 69128.5 lines/s)
-------------------------------------------------------------------------------
Language                     files          blank        comment           code
-------------------------------------------------------------------------------
Java                            12            126              6            727
-------------------------------------------------------------------------------
SUM:                            12            126              6            727
-------------------------------------------------------------------------------
```

## Next steps

Next steps are to implement proper Dataspace model entities, with
assertions and facets etc., and then build an actual Dataspace to go
with it. I'll be trying to reuse as much of this implementation style
as possible since it performs so well.