Change unsigned integer datatypes to signed about brian2cuda HOT 3 CLOSED

We briefly talked about this already, but just to put it in writing: the integer types in Brian 2's C++ code are a bit of a mess, unfortunately. We should certainly unify them at some point.
In general our approach in generated code (so this does not quite apply to the spike queue) is that the model's state variables have types with explicit sizes, e.g. int32_t and this type is used everywhere when we generate code for this variable. Explicitly written code in templates should also take this type into account with a construct like this:

{%set c_type = c_data_type(variables[varname].dtype) %}
{{c_type}} var = ...

But, we only did this where we really had to (e.g. a StateMonitor can record variables that have double, integer, or boolean types), for synapse indices we simply assume 32bit integers in many places. And then of course we often assume that int is 32bit big, which we shouldn't. Finally, the issue between unsigned and signed types is a bit tricky. I think in the beginning I often used the unsigned types for all this variables (indices, etc.) that cannot be negative, but some people with more experience in C++ than me seem to advise against it:
http://wesmckinney.com/blog/avoid-unsigned-integers/
https://google.github.io/styleguide/cppguide.html#Integer_Types

Well, there's definitely room for improvement... From the Brian 2 side, I think it would be good to deal with this at the same time as brian-team/brian2#417.

from brian2cuda.

Just referencing this brian2 merge here, which tries to avoid unsigned int in general. Right now we use unsigned int in many places and its still rather messy. So I suppose exchanging unsigned types for signed types everywhere would make sense, following above's advices.

from brian2cuda.

We are not using unsigned int anymore. We still use int32_t for some indices and int at most other places. But since this seems to not create any problems in brian2 either, we will stick with how it is right now.

from brian2cuda.