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F# performance for symbolic computation
f#

Hi all,

I recently ported an interpreter for a domain-specific
functional language from SML-NJ to F#. I was expecting
a performance boost, especially since the SML-NJ version
I was using was quite old (over 10 years: version 110.0.7,
made in 2000). But it turns out that the F# version was
several times slower. I suspected there may be something
wrong with my implementation of the interpreter,
so I decided to test another function instead, one that
simply walks down an input AST t and builds another AST t',
obtained from t by some simple symbolic massaging.
Running the F# version of that function a mere 10,000
(10^4) times took 26 seconds on my PC laptop (Intel
Core i3, 4GB DDR3, running Windows 7). By contrast, it
took 1.4 seconds in SML-NJ. I'm wondering what accounts
for such a huge performance difference. I'm running
F# from the interactive environment, the fsi.exe repl.
Should I try compiling instead? Are there any flags
I should turn on/off? Any help will be very much
appreciated - many thanks in advance.

.

Very difficult to say without any implementation details. Best advice is to compile and run your implementation through a profiler. The profiler that ships with SharpDevelop should do the trick.

By on 2/13/2011 3:13 PM ()

Hi Danny,

Discussion of this post was continued on the
thread "Performance issues, continued." I did
post actual code there, not from my project,
but some generic AST-manipulating code instead
that was fairly similar in its essence (if not its size)
to what was going on in my own code.

As far as I can tell, it appears that F# does
not fare well in that regard (see the comparison
numbers to SML-NJ, MLton, and OCaml). If there
are any theories as to why F#'s performance
on such code lags behind all three of these
other systems, and whether anything can be
done to fix it, I haven't heard any.

By on 2/13/2011 3:30 PM ()

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