I used the default ./configure options (no idea what they were).
The default's no optimization. At this point we're in development, so having a build that can be meaningfully thrown into a debugger's more important than the ultimate speed. (Besides, if we're faster without optimization, that's a good thing)
But more to the point - no one explained why the Parrot JIT ran the code 3 times slower and arrived at the wrong result.
Oh, that's easy--it's broken. :) Or possibly the JITted version keeps more stuff in the x686 floating point registers so some intermediate rounding's not going on that would happen without the JIT. I'm not sure why, but it'll require some poking around to see what's going on. Unfortunately x86 assembly's not my strong suit, so it'll end up having to wait until someone's got time to take a look at it.
--- Nicholas Clark <[EMAIL PROTECTED]> wrote:On Sat, Dec 27, 2003 at 06:17:34PM -0500, Dan Sugalski wrote: > Also, you might want to make sure you've built Parrot with > optimizations on. By default we don't enable GCC's -O to do any > optimization, and that does slow things down a bunch. On the other > hand, it makes debugging a whole lot easier. Perl 5 is built with > full optimization, so that'll make quite a difference. (Pass the > --optimize flag to Configure.pl to enable it, and expect the core ops > files to chew massive amounts of RAM and swap while it happens)
For benchmarking with gcc 3.x on x86 I'm tending to use -O2 -falign-loops=16 -falign-jumps=16 -falign-functions=16 -falign-labels=16 -mpreferred-stack-boundary=4 -minline-all-stringops
to disable the default code placement options, which as far as I can tell from the documentation chose whether to pad code to better alignments based on the amount of padding that would be needed. These defaults mean that changing the size of earlier parts of the object file can affect the alignment (and hence speed) of loops you didn't change. This is very confusing.
Nicholas Clark
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Dan Sugalski even samurai
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