[Sbcl-help] compiler speed

[Matt K. <kau...@cs...>]

Hello --

I have recently tried an experiment with a program I'm working on
(ACL2) in which I avoid explicit calls to compile-file, loading .lisp
source files instead of the resulting .fasl files before saving an
image.  In SBCL 1.0 on Ubuntu, the program's regression suite ran
significantly slower when I avoided compile-file (using the same
unloaded machine both times).  This surprised me, since my
understanding is that SBCL always compiles.  I did a similar
experiment with OpenMCL and found no such slowdown (in fact I got a
slight speedup by avoiding the compile-file calls).  Here are the SBCL
time results.

With explicit compile-file:
20300.204u 246.139s 5:44:54.95 99.2%	0+0k 0+0io 0pf+0w

Without explicit compile-file:
23021.082u 224.146s 6:30:23.08 99.2%	0+0k 0+0io 0pf+0w

Here is the optimize declaim form, which is evaluated before the
loading or compiling source files.

(declaim (optimize #+(or cmu sbcl lucid lispworks) (compilation-speed 0)
                   #+lispworks (debug 0)
                   #+cmu (extensions:inhibit-warnings 3)
                   #+sbcl (sb-ext:inhibit-warnings 3)
                   (speed 3)
                   (space #+cmu 1 #-cmu 0)
                   (safety 0)))

Any thoughts on what's going on?  Is it something as simple but
low-level as locality of code or the like?  By the way, I found in an
earlier version that a type error was missed when loading .fasl files
but was caught when loading .lisp files, so I'm wondering if some
optimization is missing when loading .lisp files.  If so, then my
model that compile-file is superfluous for SBCL is wrong (well, it's
wrong of course based on the timing results).

Thanks --
-- Matt Kaufmann