las3_pub / predictable_parallel_patterns

The strain_local resources can be used to get unique IDs for resources that would, in a serial execution, only be used once in the call chain. This is a first prototype implementation and needs further tesitng. The current implementation adds linear overhead to each steal proportional to the number of used  resources. We might be able to reduce it, but for a first version it is fine.

The flag can be used to run code annotated with PLS outside of a scheduler environment,
i.e. the app does not crash if the code is called without context. The compile option
allows to omit all spawn and sync calls during compilation, creating the equivalent serial code.

Remove easy profiler for now. It might be useful for later on to get a grasp of general behaviour, but because of its issues with coroutines it is not worth profiling code with it right now.

It is now possible to use a memory mapped stack that throws a SIGSEV if thes coroutine stacks are exhausted.

Remove the strict static memory allocation scheme in favour of placing objects on the heap at startup. This still keeps the requirements posed for modern, high performance embedded systems, but makes APIs a lot cleaner.

Older CMAKE versions wont work with export targets in different directories. For now we simply add the context_switcher manually to the export target of pls.

We still see very sporadic crashes, however the current version is at least a starting point for refactoring and debugging. Next steps have to be to re-enable tooling support (i.e. add code to let sanitizers do their work).

The current version has race conditions and is hard to debug (especially because of the fibers, if a wrong thread executes on a fiber we get segfalts very fast). To combat this mess we now refactor the code bit by bit while also adding tests where it can be done with reasonably effort).

The project is currently really messy and there are sporadic sigsevs. This indicates that we still have a race in our code. Thread Sanitizer does not work with our current implementation, as it needs annotations for fibers.

The next step is to clean up the project and maybe add thread sanitizer support to our fiber implementation. This should help finding the remaining bugs.

The deque trades tasks when stealing. Right now only the fast local path is tested and implemented. For the next step to work we also need to add the resource stack and resource tarding to the system.

The current state shows the minimum actions taken to execute a parallel call: get the thread local, find the active frame, execute on the next frame and return to the active frame.

The rationale to do an custom implementation is that the existing solutions are quite a bit slower and/or require more memory.

The basic calling works, next we measure on both x86 and arm and then decide on how we implement our fiber/'staggered stack' abstraction.

We now cover all implementations that have a chance of being fast.
ARM implementations for our 'fast fiber call' are still missing. After we add them we decide on how to proceed.

We implement a minimal concepts of user level threads. This shows the minimum requirements for our 'staggered' stack implementation: we need to be able to switch to a new stack and allow someone else to continue the calling function right before the switch.