-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
On Monday 01 June 2009 10:21:36 am David Allsopp wrote: > Dario Teixeira wrote: > > Thanks -- that is also an interesting solution. I'm guessing it will > > be faster, though it might consume more memory in cases where only one > > field is actually used. I'll have to try it side-by-side with the > > object based solution to see how they compare in the real world with my > > So as I wouldn't immediately be told "the overhead is irrelevant", I ran a > "quick" benchmark before my last post. I compared summing 7 million > 3-int-field records and 7 million 3-int-field objects using names a, b, c. > On my machine, averaged out and with enough RAM that neither paging nor the > GC get in the way, objects were nearly 3 times slower. I then tried with > 10-int-field records and objects - in this case, objects were just over 4 > times slower (read on). This was in bytecode - I didn't bother with native > code. > > The overhead of an object is 2 words (one contains tracking information > about the actual class of the object and the other is a unique identifier) > + (I think) 1 extra word for every field (because each int is boxed in a > 1-tuple so that its tag can be recorded). Importantly, accessing fields in > a record is an O(1) operation but for objects it's O(log n) for the number > of fields because a binary search is done to locate the field with the > correct tag. ocamlopt may of course optimise this search by caching the > absolute index of the field in a "recognised" object layout; I didn't look > in the compiler. My test between 3 and 10 fields would suggest that this > optimisation does not apply in bytecode. > > > David This also matches what I've seen. It seems many optimizations are not performed in bytecode. As a result, the performance characteristics of objects change dramatically when compiled to native code. In my experience objects incur a 20% hit on runtime in native code. Peng -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.7 (GNU/Linux) iD8DBQFKJAoUfIRcEFL/JewRAjlOAJ98T4OTRDy9+TxhzZ6bVuzu7pFjHACdFreL gFn1gN+whdEntNO2JcZguzQ= =1FQS -----END PGP SIGNATURE----- _______________________________________________ Caml-list mailing list. Subscription management: http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list Archives: http://caml.inria.fr Beginner's list: http://groups.yahoo.com/group/ocaml_beginners Bug reports: http://caml.inria.fr/bin/caml-bugs
