Improve flexibility of C++ standalone generated code

[thesamovar]

At the moment, the C++ standalone generated code works, but is not terribly user readable, and even less user modifiable. Some things that would improve that:

• Insert comments into the generated C++ code that correspond to the original Python code
• Collect features together into classes. For example, NeuronGroup at the moment consists of a bunch of arrays, fixed set of templates (state update, threshold, reset), and in indefinite number of initialisation statements. These could be automatically grouped together into a single NeuronGroup class. This would allow users to more easily modify generated code, e.g. to loop through a set of variables and create a NeuronGroup for each iteration of the loop.

[thesamovar]

From issue #191 which is a duplicate basically:

From Brian 2 list:

We need to support multiple runs in standalone code, or at least make
it easier to modify the code yourself. For example, rather than
generating sequential code in one long block, we could generate
functions for each run() call and then in your own code you could as it
were link to the Brian-generated code. Actually this strikes me as a
good way of designing standalone mode: we would provide a main.cpp but
the user could also write their own if they wanted more control.

[thesamovar]

I wrote some new code for C++ standalone that adds a lot of flexibility in the cpp_standalone_improvements branch. This might be of interest to @yger.

First of all, the new main() function is split into several functions defined in run.cpp. Using the CPPStandaloneDevice.run_function context manager, you can make sure that the output lines of code generated by the device are put into named functions that live in run.cpp rather than in the main() function. Combined with the ability to directly insert lines of code into main.cpp using the CPPStandaloneDevice.insert_device_code function, and the ability to add source and header files using the build method, you can now extend a generated project to do anything you want. Actually I just realised you also need to be able to add include files to main.cpp and run.cpp, but I'll add that option to build now.

[thesamovar]

This is just a quick note to myself. I also added makefiles to C++ standalone which generate a correct dependency structure which in principle saves some rebuilding if nothing changes. At the moment, it rewrites all files each time, so this doesn't help at all. However, I think if I just check that the contents of a file haven't changed before I write it, then this would solve the problem. I'm assuming that make uses the timestamps of the files rather than their contents to determine whether or not to rebuild (otherwise, it shouldn't be rebuilding on repeated runs). Hopefully with this done, iterating on development using C++ standalone should be much quicker.

[thesamovar]

OK, I fixed the issue i mentioned in the previous post. In addition to not writing files if their contents hadn't changed, I also had to make sure to sort all sorts of lists that were coming from dicts, because the order of items in a dict is randomised in recent Python versions and this was changing the contents of files. I updated the dev/ideas/devices/cpp_standalone_stdp example so that changing the duration of the run doesn't cause a recompile by using the command line arguments and inserting code. This sort of approach means it's now possible to use C++ standalone for exploring parameter spaces, for example, without having to recompile each time.

[thesamovar]

I think that's all I'm going to do on this issue for now, and maybe at all. The features in the first post are probably quite complicated for not a lot of benefit. I think the current version of C++ standalone is fully flexible now, but it would be good if someone tried it out for a real problem.

[yger]

Cool

I'll have a look asap to those changes and test them, as soon as I
understand if I could merge them with my openmp branch. But that sounds
great !

Pierre

2014-02-12 23:29 GMT+01:00 Dan Goodman notifications@github.com:

I think that's all I'm going to do on this issue for now, and maybe at
all. The features in the first post are probably quite complicated for not
a lot of benefit. I think the current version of C++ standalone is fully
flexible now, but it would be good if someone tried it out for a real
problem.

Reply to this email directly or view it on GitHubhttps://github.com//issues/152#issuecomment-34926239
.