Assignment 4 Optimizing Program Performance

Assignment 4
Optimizing Program Performance
The goal of this assignment is to optimize, in stages, the performance of a convolution reverb
program. Convolution reverb is an audio digital signal processing technique where a “dry”
recording of an instrument (i.e. a recording without reverberation) is convolved with the impulse
response of an acoustical space such as a concert hall. The result of the convolution is a sound file
where the instrument sounds as if it were playing in the actual concert hall. This is a commonly
used, but computationally intensive, technique for adding natural-sounding reverberation to
recorded sounds.
You are to create a command-line program that takes in a dry recording and an impulse response,
and produces the convolved signal. It should be invoked from the command line as follows:
convol ve inputfile I Rfile out putfile
where convol ve is the name of your program, i nputfile is the dry recording in .wav format, I Rfile is
the impulse response in .wav format, and out putfile contains the convolved signal in .wav format.
All .wav files should be monophonic, 16-bit, 44.1 kHz sound files (at least initially, before
attempting the bonus part of the assignment).
Baseline Program
Create an initial version of your program where the convolution is implemented directly in the
time domain (i.e. use the input-side convolution algorithm found on p. 112-115 in the Smith text).
You will find this version of your program quite slow. Measure the run-time performance of your
program using a dry recording that is at least thirty seconds long, and an impulse response that is
at least 2 seconds long. You will reuse these same inputs for timing measurements after each
optimization that you do in the later stages of the assignment. There are many suitable dry
recordings and impulse responses available on the Internet as well as on the course D2L site. You
can use utility programs such as sox to convert sound files of different types (e.g. .aiff or .snd) to
the .wav format.
Although the program may be implemented in any programming language, it would be best to use
a language supported by the gcc compiler, since it is available on our servers, or can be installed
on a home machine. The gcc compiler supports the C, C++, and Objective-C languages.
Algorithm-Based Optimization
Create a second version of your program where you re-implement the convolution using a
frequency-domain convolution algorithm. A good candidate is the overlap-add FFT convolution
algorithm described on p. 311-318 in the Smith text, although you can try other algorithms if you
wish. You can also experiment with different Fast Fourier Transform (FFT) algorithms. Measure
the run-time performance of this second version of program using the same inputs that you used
for the baseline program. Be sure to use version control and regression testing as part of a
disciplined process of optimization.
Compiler-Level Optimization and Code Tuning
Use compiler-level optimization and manual code tuning to further optimize the performance of
your program. Do your improvements step by step, measuring and testing at each stage. Be sure
to use version control and profiling as you make changes. Use at least 5 different manual codetuning
techniques and at least one compiler optimization.
Report
Create a formal written report that describes how you optimized your code at each step. You must
show each version of your program, and describe what changes you made at every stage of the
process. You must also quantify the improvements with your timing measurements, and show the
regression tests you did. Use tables and/or graphs to help illustrate how you improved
performance at each stage of your work.
Bonus #1 (up to 5%)
Elaborate your program so that it can handle stereo (i.e. 2-channel) impulse response files, and
produce the appropriate stereo (2-channel) output file. In other words, your program will
convolve a monophonic dry input sound with a stereo impulse response, and output a stereo
sound file. Your program should be able to recognize automatically if the impulse response file
has one or two channels.
Bonus #2 (up to 5%)
Elaborate your program so that it can deal with .aiff and .snd file formats, both for input and
output. These formats should be automatically recognized using the suffixes appended to the
filename and the headers in the files. For example, convolve input.aiff ir.snd out put. wav specifies
.aiff format for the dry signal, .snd format for the impulse response, and .wav for the output file.
Submit the following to the D2L Assignment 4 Dropbox:
1. An electronic copy of your report (in Word or PDF format). Be sure you include all
supporting materials, including all versions of your program code, version control log reports,
timings, profiler reports, and regression tests.
2. An electronic copy of your source code. Your TA will compile and run your program to
confirm it does the convolution reverberation processing correctly. Be sure it can be run from
the command line as described above.
3. If you do any of the bonus parts, a copy of the corresponding source code for your program.
Indicate in your report if you are doing any of the bonus parts.
Advanced Programming Techniques
Assignment 4 Grading
Student:__________________________________________
Baseline program 4 ______
Algorithm-Based Optimization 8 ______
Minimum of 5 manual code tunings 10 ______
Minimum of one compiler optimization 2 ______
Profiling 6 ______
Timing measurements 6 ______
Regression Tests 6 ______
Version control 5 ______
Program Design Quality 5 ______
Report 10 ______
Total 62 ______ _____%
Bonus #1 5% _____%
Bonus #2 5% _____%
Grand Total _____%