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povray: a benchmark with mainline, tree-ssa, and icc
- From: Scott Robert Ladd <coyote at coyotegulch dot com>
- To: gcc mailing list <gcc at gcc dot gnu dot org>
- Date: Sat, 17 Jan 2004 15:01:26 -0500
- Subject: povray: a benchmark with mainline, tree-ssa, and icc
Given some questions posed in the "Contributing tree-ssa to mainline"
thread, I decided to run a little benchmark.
The target of the benchmark is povray, a well-known ray-tracing program
that is also getting some heavy use in my household at the moment. I
pulled fresh source code for version 3.50c from their web site at
http://www.povray.org. I used the official povray "benchmark.pov" with
the settings in "benchmark.ini".
I ran these tests on a 2.8GHz Pentium 4 (Northwood) with 512MB RAM,
under Linux 2.6.0, using mainline and tree-ssa code pulled form CVS mere
hours ago. I also included results for Intel C++ 8.0, as a matter of
All times are in minutes:seconds, as reported by povray's internal
timer. Switches used were:
gcc: -O3 -march=pentium4 --finline-functions
-ffast-math -fomit-frame-pointer -funroll-loops
icc: -O3 -xN -tpp7 -ipo
The GCC switches are the default defined by povray, with the exception
of my changing the -march switch to specify the Pentium 4. I chose the
ICC switches myself.
A drum-roll, please.
gcc mainline 1:43 7:59
gcc tree-ssa 2:40 7:24
icc 8.0 1:53 5:50
I don't find these numbers comforting.
Tree-ssa is substantially slower at compiling than mainline, although it
does produce slightly faster code.
The ICC numbers speak for themselves. Yes, I verified the output as correct.
CAVEAT: This is only *one* platform, albeit a popular one, and only one
benchmark. I'm going to run a full set of tests in the next few days,
all on real world code.
Is povray a good benchmark? I think so, at least in terms of the kind of
work I do, which is mostly number crunching.
Some anecdotal observations: On a DSP application for one of my clients,
ICC is consistently 20% faster than GCC; tree-ssa offers a 5%
improvement over mainline. Alas, the application is under NDA, so I
can't provide more details. I do know that, with a very few exceptions,
the povray numbers above reflect the relative performance of these
compilers on my projects.
I realize some people do not see ICC as a valid competitor... however, I
don't see why GCC can't at least approach ICC's level of performance.
At this point, tree-ssa is a marginal improvement over mainline in code
quality, and a significant regression in terms of compile speed. Those
who know tree-ssa may have some insight into whether or not more
optimization can be squeezed out while also improving compile time.
Scott Robert Ladd
Coyote Gulch Productions (http://www.coyotegulch.com)
Software Invention for High-Performance Computing