So one of my goals in developing DALIS/H2D2 was to make it possible to run a single instance of a program on multiple platforms. Since the H2D2 virtual machine can run code for a timeslice and then persist the entire state of the running program, it should be possible to put an executing H2D2 program into hibernation, move it to a different platform (ie a machine with an entirely different type of OS or processor) and then carry on running the same program. No matter what point the program was frozen at, the code should be able to carry on where it left off.
Well I've now gotten to the point where I can test that theory. The first experiment is to run a program on Windows for a few milliseconds and then complete the execution on Linux. To make this work I needed to make sure that all my data was persisted in sizes that are the same on different platforms, so I need to use
int32_t instead of
int, that type of thing. Since I've written my code in a cross-platform way and since I'm using data sizes that will be the same on different platforms everything should just work. So here we go, I'm running my mandelbrot program on Windows for 200ms:
...so that outputs a file called 'demo.hby' which is the H2D2 bytecode including its persisted state (all the program instructions, the call and data stacks and the values of all variables). Now I need to move that file to my Linux box and run the code from where it stopped. On the Linux machine I have already compiled the H2D2 virtual machine from source using GCC of course. Here goes:
Awesome! It works! I guess it's not much more than a neat trick at the moment, but I think it's an achievement of sorts. If you had some kind of long running process, it might be handy to be able to wake it, run it on whatever machine was available, and then put it back into hibernation. Okay, you can't start re-writing all your business logic in H2D2 just yet... but it's early days. This is why I always imagined DALIS / H2D2 to be a cloud based language, where you don't care what type of platform or processor is being used from one moment to the next.
So the next obvious experiment is to do the same thing, but on the Raspberry Pi... maybe I'll do it in reverse, by starting the program on the Raspberry Pi and then finishing it on Windows.