Hello!

I've performed a few simple tests using Haskell and C++ on primitives.

I've compilled all Haskell programs with -O2 optimizations, and C++ ones with -O3

ghc version - 7.10.2, gcc version : 5.1.1

I'm sending the codes in the zip file.

Problem1 - 100 000 000 iterations.

Time of execution (in seconds):
Int pure tail recursion: 6.911011299962411e-2
Int# pure tail recursion : 4.587398100011342e-2

IORef for loop 1.1533970820000832

IORef 'tail' recursion 1.0696569040001123

STRef for loop 1.1545546840006864

STRef tail recursion 1.1110019479992843

C++ : 2.7e-07

The llvm version could be as fast as C++ one in this problem.

Buuut... then there's problem 2 (using if or case) - 100 000 000 iterations:

Int# tail recursion 1.315346227000191

IORef for loop: 2.6442542390004746

STRef for loop: 2.669217500999366

C++: 0.158056

Here haskell is about 9 times slower than C++.

Problem 4 - executing the same functionality using bit operations - 100 000 000 iterations:

Int# tail recursion: 0.12361123500068061

C++: 0.131141

So, Haskell here is as fast as C++.

My question is: can IORefs and STRefs be optimized ? I would like very much to rely on them, but I would like to achieve great speeds.

Also, is can one achieve good speeds of execution when using cases or ifs ? If not, what is the other way to do it ? Compiler flags, Cmm optimizations - they are all welcome.

And the final question - how hard would it be to implement such optimizations in ghc compiler?

Regards,

Mateusz Kłoczko