Is this just compiler optimized memoization? I mean this is great for parallelization as well but I thought this was standard in the functional programming paradigm. Maybe I am wrong.
As I recall, memorization usually involves associating the results of calling a pure function with the particular input values so the computation of the function is reduced to a lookup operation.
The calculation of the pure function is still used for any other combination of input values.
Supercompilation looks at the unevaluated symbolic recursive code and replaces the code in some cases with simpler, specialized code tuned to the actual input values, so does a memoizing not only of the result, but the code used to calculate the function to begin with.
There are currently no production-grade compilers that make use of supercompilation in the functional world. Memoization is about caching results of pure functions; supercompilation is about deep program transformation.
Any idea why there aren't? Not even to a small degree? To me, it looks like fairly straight-forward rewriting. Perhaps it's hard to tell how much is useful?
> deep program transformation
It doesn't have to be deep, does it? You can't transform the entire program, so there's an arbitrary cut-off anyway.
I think there are a few big problems. Performance is a big one, code bloat is another. You also need a very good termination heurestic or there will be edge cases where compilation time spins out of control.
Supercompilation acts as global program optimization. As far as I'm aware, there were no attempts to supercompile separate libraries.
In fact, supercompilation subsumes many common optimizations, such as function inlining, constant propagation, list fusion, etc. So we can say that it's actually used "to a small degree", although I wouldn't really call it "supercompilation" per se.
The reason that full-blown supercompilation is not used is that it's too unpredictable -- the direct consequence of being too smart. I've elaborated on it in the final section of the blog post.
The calculation of the pure function is still used for any other combination of input values.
Supercompilation looks at the unevaluated symbolic recursive code and replaces the code in some cases with simpler, specialized code tuned to the actual input values, so does a memoizing not only of the result, but the code used to calculate the function to begin with.