ANN: HIntegerByInt

[Isaac Dupree]

Isaac Dupree wrote:

> John Meacham wrote:
>  > Excellent! this has always been a project I wanted to do in the back
>  > of my mind. I will likely make it the default Integer implementation
>  > for jhc. I look forward to the fun compiler optimizations it will
>  > inspire to make it speed comparable to gmp

Actually we have a few advantages over GMP:

We can do inlining, and analysis for static knowledge (e.g. small 
numbers or nonzero numbers), much more than in C, which knows nothing 
about its bignum type.  Probably this would work best with some 
knowledge baked into the compiler about the meaning of Integer 
operations (like the way GHC has metadata along with the definitions of 
its primitives, at least whether they're symmetric operations...) 
(Unless some way to specify that with compiler pragmas is invented, but 
computing with Integers may be a bit of a special case.)  I want to see 
compilers do more sophisticated constant folding (generally, computation 
at compile time), which has to watch out for non-pure, non-safe and 
non-total (nonterminating) functions as well as deciding whether some 
partial computation will reduce code size and improve speed, or just 
bloat it.

We can make a higher-level library/type, that relies on any Integer 
implementation, and gives a type that does not evaluate immediately, so 
optimizations (runtime) can be done on series of operations.  Er... the 
Integer type would probably have to provide operations that were more 
efficient and did weird things -- either a Haskell Integer 
implementation or GMP's mpn layer would probably be useful. (Haskell is 
a particularly good language for things like this, I think... if it is 
likely to be useful... It is useful for matrix operations in C++ :))


Another thing I was wondering is whether there's any point making it be 
able to work on the GMP-integer representation that GHC stores 
internally... probably not much.

Isaac