Optimization of IORefs and STRefs - comparison to g++

[Mateusz Kłoczko]

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
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