This is the second of two assessed coursework exercises, both based on
SUSAN edge detector.
You may work in groups of two or three if you wish, but your report must
include an explicit statement of who did what.
Deadline: Monday 7th March. Submit your work electronically via CATE.
Copy the source code directory tree to your own directory:
cp -r /homes/phjk/ToyPrograms/ACA05/Susan ./
Now compile the susan.c program:
Now you can run the program:
time ./susan.x86 Ins/input_Cupboard.pgm Outs/Cupboard.pgm -e
This reads input from the file Ins/input_large.pgm, and
writes its output to the Outs directory. Both input and
output files are in PGM (Portable Gray Map) format (see ``man
pgm''. The ``time'' command runs the command line and reports
how much elapsed, user and system time it took.
You have been provided with a selection of input files of various sizes:
input_small.pgm (76x95 pixels; from Susan distribution)
input_large.pgm (384x288 pixels; from Susan distribution)
If you need a larger one, see /homes/phjk/ToyPrograms/ACA05/Susan_ExtraImages.
Basically, your job is to figure out how to run
susan as fast as you possibly can,
and to write a brief report explaining how you did it.
- You can choose any hardware platform you wish.
You are encouraged to find interesting and diverse
machines to experiment with. The goal is high
performance on your chosen platform
so it is OK to choose an interesting machine
even if it's not the fastest available.
On linux type ``cat /proc/cpuinfo''.
Try the Apple G5s, possibly PDAs, DSP processors, graphics
co-processor or FPGA.
- Make sure
the machine is quiescent before doing timing experiments.
Always repeat experiments for statistical significance.
- Choose a problem size which suits the performance of the
machine you choose - the runtime must be large enough
for an improvements to be evident. You might also
enjoy working with video - if so you will need to
set up the experiment. You are very welcome to
explore Susan's performance in its other modes, ``-s'' for smoothing,
``-c'' for corners.
- The numerical results reported by the application
need not be absolutely identical, but if not you must
justify the correctness of your results1.
- You can achieve full marks even if you do not
achieve the maximum performance.
- Marks are awarded for
- Systematic analysis of the application's behaviour
- Systematic evaluation of performance improvement hypotheses
- Drawing conclusions from your experience
- A professional, well-presented report detailing the
results of your work.
- You should produce a compact report in the style of an academic paper for presentation at an
international conference such as Supercomputing (www.sc2000.org).
The report must not be more than 7 pages in length.
You may find it useful to find out about:
- AMD's CodeAnalyst (installed on CSG Athlon machines -
StartProgrammingAMD) (if you have an
- Cachegrind and cg_annotate
- gprof - standard command-line profiling tool.
- kprof - kprof.sourceforge.net - graphical interface to gprof
- kcachegrind - kcachegrind.sourceforge.net - graphical interface to cachegrind
- VTune - Intel's (Windows and Linux) tool for understanding
CPU performance issues and mapping them back to source code
(http://www.intel.com/software/products/vtune/). Free trial.
- Sun's Performance Analyzer
(if you have a Sun Sparc machine)
http://oprofile.sourceforge.net/news/ (requires kernel rebuild)
You could investigate the potential benefits of more sophisticated compiler
- Intel's compilers
installed on various Linux systems in the Department).
- Codeplay's compilers (www.codeplay.com) (free demo download?)
- IBM's compilers for Apple G5 - XL C/C++ Advanced Edition (a beta download was available, possible donation from Apple or IBM?)
You are strongly invited to modify the source code to investigate
performance optimisation opportunities. You might wish to start with
a cleaned-up version of the code, called ``susan_arrays.c''.
Susan's brightness lookup table ruins performance on some platforms,
such as GPUs but you could try doing the calculation (or approximating
it) in the loop. Note that most of the lookup table entries are zero
(and many of the rest are 1).
The main criterion for assessment is this: you should have a
reasonably sensible hypothesis for how to improve performance, and you
should evaluate your hypothesis in a systematic way, using
experiments together, if possible, with analysis.
Hand in a concise report which
Please do not write more than seven pages.
- Explains what hardware and software you
- What hypothesis (or hypotheses) you investigated,
- How you evaluated what the
potential advantage could be,
- How you explored the effectiveness
of the approach experimentally
- What conclusions can you draw from your work
- If you worked in a group, indicate who was responsible for
Paul Kelly, Imperial College, 2005
- ... results1
- The gcc flag -ffloat-store is sometimes useful to check whether the difference in output is
due purely to register allocation.
- ... machine)2
- To use this, use a Windows machine and
copy the susan.x86.cygwin-gcc3-3-3.exe or susan-msvc-clv12.exe
version of the code (and