Franck Pommereau

This release introduces a first version of a graphical ABCD simulator. Invoking command abcd with option --simul yields a window in which you may execute your ABCD code interactively, going back and forth into the trace executed so far. The top-right panel shows the source code, with the currently executable actions highlighted. The top-left panel shows all the currently executable actions with their modes. Here, we have selected one of the modes of the odd() net action, so it is highlighted in green. The bottom-right panel shows the current state of buffers. Finally the bottom-left panel shows the current trace; clicking on an action in this trace puts the other panels into the states corresponding to when the action had just been executed. (A special action allows to observe the initial state.) Using the buttons on the middle-left, you may execute a selected action, remove the last action from the trace, or resume simulation when you are done with trace inspection (which selects the last obtained state).

Moreover, a reachability checker has been introduced also. It is still very suboptimal since it computes the reachability graph by directly using SNAKES firing, future version will improve efficiency using model compilation and introduce CTL* model-checking. Right now, to check properties, just insert assertions at the very end of your ABCD spec, for instance assert 5 not in _["buff"] allows to check that no token whose value is 5 is ever inserted into buffer buff, where _ is simply a Marking object and "buff" is a buffer name (including the instance path for buffers nested into nets, just as show in the bottom-right panel of the simulator). Then, using option --check, the state space of the Petri net corresponding to the ABCD model is computed and each assertion is checked against every reachable state. Whenever a state that violates an assertion is reached, a trace from the initial state to this error state is printed and the analysis stops immediately. If you combine --check with --simul, such an error trace is displayed in the simulator instead of on your terminal.

Finally, this release fixes several bugs, in particular a blocking bug on transitions firing that appeared with the latests releases of Python.

As usual, you may download the source code or install the Ubuntu package.

This new version successfully passes the tests under Python 3.2, only the doctests have been passed, so there is probably still undetected compatibility problems. Notice that tests fail on Python 3.1, but presumably everybody already has 3.2 considering how long 3.1 has existed. Other changes in this release include small bug fixes and a new ABCD example (dinning philosophers).
So far, SNAKES is compatible with Python 2.5 to 3.2 (except 3.1), Pypy (at least 1.5 because 1.4 has a blocking bug), Stackless and Unladen Swallow. Currently, Jython compatibility is broken (on exactly the same problem that broke Pypy 1.4).
As usual, you may download the source code or Ubuntu packages.

I've been asked a few times how SNAKES version are numbered. As for many software, it is major.minor.revision. But I currently stick with major=0 and reached minor=9 already, so I'm currently only incrementing the revision number. Before to move to major=1, I'll wait to have the following changes implemented:

• PNML support replaced: a Python implementation of the PNML standard is in progress, it will fully implement and respect the standard. I will release it independently of SNAKES, and then update SNAKES to rely on this new library.
• Full API documentation and doctests for every class, method and function. I wish I could export it into Google code wiki format to have proper on-line documentation. For hand-written parts of the doc, I should move from AsciiDoc to Sphinx.
• Further polishing of some parts, in particular, the plugin system needs to be simplified a bit.

This new version features a complete rewrite of the ABCD compiler. The main visible changes are:

My home page at LACL does not exist any more: I've moved to IBISC as a professor and built a new home page there. I've migrated most of the old content except:

• publications that have been hosted since a few months on this blog;
• outdated pages;
• SNAKES API reference manual since it is distributed together with SNAKES.

I also plan to host a copy of SNAKES API on SNAKES development page (as soon as I have finished the script to convert it in wiki format).